田中　秀樹 （タナカ　ヒデキ）

コミュニケーション情報 byコメンテータガイド

• コメント

  ウナギの産卵、孵化、仔魚飼育の研究を行っています。養殖に使う天然の稚魚（シラスウナギ）の安定供給が心配されていますが、天然に依存しない完全養殖の実用化を目指しています。

• 報道関連出演・掲載一覧

  ＜報道関連出演・掲載一覧＞ ●2023/12/11 　中日こどもウィークリー 　ウナギの完全養殖について ●2023/11/23 　TOKYO FM「ONE MORNING」 　ウナギの完全養殖について ●2023/11/19 　東京新聞　 　ウナギの完全養殖について ●2023/1１/３ 　日刊工業新聞　 　ウナギの完全養殖について ●2023/11/1 　みなと新聞　 　ウナギの完全養殖について ●2023/7/25 　読売テレビ「かんさい情報ネットten.」 　ウナギの完全養殖に向けた研究について ●2023/7/23 　BSフジ「ガリレオX」 　「ウナギの完全養殖技術」について ●2022/8/3 　BSよしもと「ワシんとこ・ポスト」 　ニホンウナギの人工養殖の難しさについて ●2021/7/28 　テレQ九州放送「ふくサテ！」 　「シラスウナギの漁獲量」と「今年のうなぎの価格」との関係について ●2020/7/29 　読売テレビ「かんさい情報ネットten.」 　ニホンウナギの完全養殖について ●2020/7/23 　読売テレビ「朝生ワイドす・またん！」 　ウナギの完全養殖について ●2020/7/8 　毎日放送「ミント！」 　「シラスウナギ」漁が不漁だった去年からV字回復している理由について ●2019/12/16 　テレビ和歌山「6時のわかやま」 　ウナギの人工ふ化　初期飼育の成功について ●2019/11/28 　毎日放送「ミント！」 　ウナギの養殖研究について ●2019/11/11 　関西テレビ「報道ランナー」 　ウナギ孵化成功について ●2019/8/22 　テレビ朝日「超人女子戦士ガリベンガーV」 　うなぎの謎に包まれた生態について ●2018/4/18 　関西テレビ「みんなのニュース　報道ランナー」 　シラスウナギの減少の原因について

研究者情報

学位

• 博士（京都大学）

ホームページURL

https://jglobal.jst.go.jp/detail?JGLOBAL_ID=201801012158977040

J-Global ID

• 201801012158977040

プロフィール

• 大阪府出身

研究キーワード

• 魚類繁殖生理   ウナギ   水産養殖   

現在の研究分野（キーワード）

ウナギの産卵、孵化、仔魚飼育の研究を行っています。養殖に使う天然の稚魚（シラスウナギ）の安定供給が心配されていますが、天然に依存しない完全養殖の実用化を目指しています。

研究分野

• ライフサイエンス / 水圏生産科学 / 水産増養殖学

経歴

• 2018年04月 - 現在  近畿大学水産研究所浦神実験場教授
• 2016年04月 - 2018年03月  国立研究開発法人 水産研究・教育機構 増養殖研究所ウナギ種苗量産研究センター量産基盤グループ長
• 2011年04月 - 2016年03月  独立行政法人水産総合研究センター 増養殖研究所養殖技術部ウナギ量産研究グループ長
• 2004年04月 - 2011年03月  独立行政法人水産総合研究センター 養殖研究所生産技術部繁殖研究グループ長
• 2003年04月 - 2004年03月  独立行政法人水産総合研究センター 養殖研究所生産技術部ウナギ種苗研究チーム長
• 2002年04月 - 2003年03月  独立行政法人水産総合研究センター養殖研究所繁殖部初期発育研究室長
• 1991年04月 - 2002年03月  水産庁養殖研究所繁殖生理部主任研究官
• 1982年04月 - 1991年03月  水産庁養殖研究所繁殖生理部研究員

学歴

• 1980年04月 - 1982年03月   京都大学大学院   農学研究科   水産学専攻
• 1976年04月 - 1980年03月   京都大学   農学部   水産学科

所属学協会

• 日本魚類学会   日本水産学会   

研究活動情報

論文

• Diets comprising hen egg yolk and milk proteins as potential alternatives to shark egg-based diets for larvae of the Japanese eel Anguilla japonica

  Hirofumi Furuita; Tadao Jinbo; Masato Higuchi; Kazuharu Nomura; Ryusuke Sudo; Hiroyuki Matsunari; Koji Murashita; Hiromi Oku; Takeshi Yamamoto; Hideki Tanaka

  Fisheries Science 2024年 

  The only diet that has been capable of rearing eel larvae to the glass eel stage in captivity is the shark egg (SE)-based diet (SE). This study investigated the potential of alternative dietary components, namely hen egg yolk (HEY), milk proteins, and fish protein hydrolysate (FPH), on the growth and survival of eel larvae. In the first experiment, a diet containing HEY and skimmed milk powder (HS) was compared to SE. There were no significant differences in growth and survival rate between the two diets except in the early part of the experiment period. In the second experiment, HS was modified by the addition of FPH and casein (FC), and larval performance was evaluated for three dietary regimens (SE, HS, and FC). The performance of larvae fed HS and FC was found to be comparable or superior to those fed SE. It was observed that larvae fed the alternative diets to SE were able to progress to glass eels. However, more skeletal abnormalities were observed in HS in experiment 1. The results of this study indicate that a combination of HEY and milk proteins is suitable as a larval eel diet, and that it has the potential to replace SE.
• Effects of long-term feeding of fishmeal-free diet on growth parameters, bile acid status, and bile acid-related gene expression of yearling red sea bream Pagrus major (Temminck & Schlegel, 1843)

  Fumiaki Takakuwa; Koji Murashita; Yoshitsugu Noguchi; Takashi Inui; Kosei Watanabe; Shoya Sugiyama; Shinichi Yamada; Amal Biswas; Hideki Tanaka

  Aquaculture 570 2023年05月 [査読有り]
   

  We evaluated the effects of long-term feeding of a fishmeal-free (FMF) diet on the growth parameters and physiological status, especially the bile acid status, of red sea bream (Pagrus major) yearlings. Two isonitrogenous and isolipidic diets were prepared; a fishmeal-based diet as the control, and an FMF diet containing soybean meal, corn gluten meal, soy protein concentrate, and pea protein concentrate as plant-derived ingredients, and poultry by-product meal and feather meal as animal-derived ingredients. Six hundred red sea bream yearlings were accommodated in six net cages, and the two experimental diets were hand-fed for 36 weeks. Throughout the 36-week trial, mean body weight and feed intake were significantly lower in the FMF group than in the control group. The concentrations of serum total cholesterol and high-density lipoprotein cholesterol were also significantly lower in the FMF group than in the control group throughout the trial. The total bile acid amount per fish was significantly lower in the FMF group than in the control group between Week 32 and 36 when the water temperature was the lowest (14.3–17.2 °C). Gene expression levels of hepatic cyp7a1 and cyp8b1 tended to be lower in the FMF group than in the control group from Week 20 to the end of the trial. Expression levels of hepatic sqle were higher in the FMF group than in the control group through the trial period and were markedly high at Week 36. Expression of hmgcr was also higher in the FMF group than in the control group at Week 32 and 36. The hindgut asbt expression of fish fed the FMF diet was lower than those fed the control diet at Week 28 and 32. These results suggest that the long-term feeding of an FMF diet to red sea bream yearlings causes reduced growth due to a significant reduction in feed intake and bile acid production, and enterohepatic circulation are strongly disturbed when water temperatures are low from autumn to winter.
• Total Replacement of Fish Meal by the Combination of Fish Residue Meal and Soy Protein from Soymilk in the Diet of Red Sea Bream (Pagrus major).

  Amal Biswas; Yuta Takahashi; Kota Isaka; Fumiaki Takakuwa; Hideki Tanaka; Kenji Takii

  Animals : an open access journal from MDPI 12 23 2022年11月 [査読有り]
   

  Three experiments were performed to explore (i) the complete replacement of fish meal (FM) with a combination of fish residue meal (FRM, 65% round discarded fish + 35% byproduct), soy protein concentrate (SPC) from soymilk and corn gluten meal (CGM) in Trial 1 and (ii) the utilization of diets composed of increasing byproducts in FRM in the summer (Trial 2) and winter (Trial 3) seasons. In Trial 1, the ratio of (SPC + CGM):FM in the control diet (C) was 8:2. The FM component from diet C was replaced with FRM (diet, RM20), where the ratio of (SPC + CGM):FRM became 8:2, and this ratio was changed to 6:4, 4:6 and 2:8, and referred to as RM40, RM60 and RM80, respectively. In Trials 2 and 3, the ratios of round discarded fish and byproducts in FRM were adjusted to 65:35 (FRM1), 30:70 (FRM2) and 0:100 (FRM3), and the FRM component from diet RM40 in Trial 1 was replaced with FRM1, FRM2 and FRM3 to formulate diets RM1, RM2 and RM3, respectively. In Trials 1, 2 and 3, rearing periods were 10, 8 and 12 weeks, respectively. In Trials 1 and 3, there were no significant differences in growth parameters, nutrient retention efficiency or plasma constituents among the treatments, irrespective of the inclusion levels of FRM in the diets (p > 0.05). Although there were no significant differences in final mean weight (p > 0.05), daily feeding rate and feed conversion ratio in diet RM3 were significantly higher and lower, respectively, compared to the control group in Trial 2 (p < 0.05). These results suggest that FM can be entirely replaced with FRM, and that the total elimination of round discarded fish from FRM does not affect growth or health status in red sea bream either in summer or winter seasons.
• Bioavailability of porcine blood meal as a fish meal substitute in the diet for red sea bream ( Pagrus major , Temminck & Schlegel) fingerling

  Fumiaki Takakuwa; Hisao Sato; Naohiro Mineyama; Shinichi Yamada; Amal Biswas; Hideki Tanaka

  Aquaculture Research 53 13 4616 - 4626 2022年09月 [査読有り]
  
• Low- and high-temperature processed potato protein concentrates as alternatives to fishmeal in greater amberjack Seriola dumerili diets

  Fumiaki Takakuwa; Keinosuke Suzuri; Hiroaki Mikotaka; Shinichi Yamada; Amal Biswas; Hideki Tanaka

  Fisheries Science 88 5 581 - 592 2022年09月 [査読有り]
  
• Effect of additional heating of fish meal on in vitro protein digestibility and growth performance of white trevally (Pseudocaranx dentex) juveniles

  Fumiaki Takakuwa; Shota Hayashi; Shinichi Yamada; Amal Biswas; Hideki Tanaka

  AQUACULTURE RESEARCH 53 4 1254 - 1267 2022年03月 [査読有り]
   

  Fish meal (FM) used in fish farming is prepared by steaming, squeezing, defatting, drying and crushing raw fish material. However, how drying affects protein digestibility has not been systematically studied. Herein, we evaluate the effect of additional heating of FM on in vitro FM protein digestibility and growth performance of white trevally (Pseudocaranx dentex) juveniles. We heated conventional steam-dried Chilean FM from 50-200 degrees C for 1 h to prepare additionally heated FM (AHFM). In-vitro AHFM protein digestibility started to decrease significantly above 150 degrees C, along with substantial reduction in the protein digestion speed. Five isonitrogenous/isolipidic experimental diets were prepared by substituting different proportions of FM with AHFM produced by heating FM to 180 degrees C. In-vitro protein digestibility and digestion speed of the experimental diets decreased linearly with increasing AHFM content. After a 33-d feeding trial, the final bodyweight, specific growth rate, weight gain and feed efficiency of white trevallies decreased linearly and/or quadratically with increasing dietary AHFM levels. These findings indicate that in vitro protein digestibility of AHFM decreases linearly at temperatures above 150 degrees C, and the growth and feed efficiency of white trevallies are negatively affected by dietary inclusion of AHFM processed at 180 degrees C.
• Production of recombinant Japanese eel (Anguilla japonica) growth hormones and their effects on early-stage larvae.

  Ryusuke Sudo; Yutaka Kawakami; Kazuharu Nomura; Hideki Tanaka; Yukinori Kazeto

  General and comparative endocrinology 317 113977 - 113977 2022年01月 [査読有り]
   

  Growth hormone (Gh) regulates somatic growth in fishes, particularly through the Gh - insulin-like growth factor-I (Igf-I) axis. In this study, recombinant Japanese eel Ghs with or without C-terminal peptides of human chorionic gonadotropin (CTP), which are known to prolong the half-life, were produced using the HEK 293 and CHO expression system. The effect of recombinant Gh administration to eel larvae on their somatic growth was investigated in short-term feeding experiments, and it was found that three types of recombinant Ghs with CTP (CTP-reGh, reGh-CTP and reGh-CTP × 2) were more effective in promoting somatic growth in eel larvae than recombinant Ghs without CTP. Among the three recombinant Ghs with CTP, reGh-CTP × 2 had the highest growth-promoting effects, however only when provided in the short term. After long-term administration of reGh-CTP × 2, there was no difference in growth between the Gh administrated group and the control group. The survival rate of eel larvae were not affected by recombinant Ghs. In addition, the mRNA expression of gh, Gh receptors, Igf-I and IGF-II were measured by quantitative real-time PCR, and significant reductions in the expression of gh, Gh receptors and Igf-I were observed. These findings provide useful tools to study the mechanisms of somatic growth and increase understanding of Gh regulation in anguillid eel larvae.
• Correction to: Effects of rearing temperature manipulation on oocyte maturation progress in Japanese eel (Fisheries Science, (2021), 87, 5, (681-691), 10.1007/s12562-021-01531-8)

  Toshiomi Tanaka; Shinji Adachi; Kazuharu Nomura; Hideki Tanaka; Tatsuya Unuma

  Fisheries Science 87 5 693 - 695 2021年09月 

  In this article the black down arrows in Fig. 2a, that should indicate white letters ‘20 °C’ inside the arrows have disappeared. It should have appeared as shown below. The original article has been corrected.
• Effects of rearing temperature manipulation on oocyte maturation progress in Japanese eel

  Toshiomi Tanaka; Shinji Adachi; Kazuharu Nomura; Hideki Tanaka; Tatsuya Unuma

  Fisheries Science 87 5 681 - 691 2021年09月 [査読有り]
   

  During the induction of Japanese eel maturation, administering maturation-inducing steroids (MIS) or their precursors at an inappropriate maturational status is a major cause of poor egg quality. In this study, we investigated the feasibility of controlling oocyte maturation progress by rearing in cold and warm water to manipulate the timing of MIS administration. Mature females with oocytes at the migratory nucleus stage were reared for two terms (3 days to 1 day and 1 day to 0 days before MIS administration) at 20/20 degrees C, 20/15 degrees C, 15/20 degrees C, or 15/15 degrees C, and the maturational status was monitored based on their lipid droplet morphology and oocyte diameter. Oocytes matured faster at 20 degrees C than at 15 degrees C in either term. Next, the mature females were reared at 15 or 20 degrees C depending on the maturational status of each female 3 days and 1 day before MIS administration; the immature females were reared at 20 degrees C to accelerate their maturation. Consequently, the maturational status of most females was similar at MIS administration. After improvement, this method would lead most females to the optimum maturational status at MIS administration by properly rearing in cold and warm water.
• Availability of black soldier fly meal as an alternative protein source to fish meal in red sea bream (Pagrus major, Temminck & Schlegel) fingerling diets

  Fumiaki Takakuwa; Ryota Tanabe; Shohei Nomura; Takashi Inui; Shinichi Yamada; Amal Biswas; Hideki Tanaka

  AQUACULTURE RESEARCH 53 1 36 - 49 2021年08月 [査読有り]
   

  Black soldier fly meal (BM) is an outstanding candidate as a fish meal (FM) substitute because it contains relatively high protein and essential amino acids. In this study, we replaced FM in red sea bream diets (Pagrus major) with BM to investigate its effect on growth and feed utilization. Six isonitrogenous and isolipidic experimental diets were prepared by substituting 0%, 20%, 40%, 60%, 80% and 100% FM protein with BM (Control, BM20, BM40, BM60, BM80 and BM100, respectively). After the 8-week feeding trial, final body weight, weight gain, specific growth rate and feed efficiency decreased linearly with increasing dietary BM level (p < 0.05). Apparent digestibility of protein and fat and serum total cholesterol concentration decreased with increasing dietary BM levels (p < 0.05) Final body weight, WG, SGR and FE against dietary BM level had breaking points of 76.2%, 41.7%, 76.5% and 60.0%, respectively, in segmental regression analysis. In conclusion, the results suggest that BM can replace a maximum of 41.7% of FM in the diet of red sea bream without compromising growth performance or feed efficiency for 56 days.
• Partial replacement of fishmeal by a protein-rich product from methanotrophic bacteria in juvenile red sea bream (Pagrus major)

  Amal Biswas; Fumiaki Takakuwa; Shinichi Yamada; Asuka Furukawa; Masaru Shiratori; Tomohiko Koshiishi; Hiroyuki Tomokane; Hideki Tanaka

  Aquaculture Nutrition 2021年 [査読有り]
   

  The optimum level of fishmeal (FM) protein replacement by bacterial protein meal (BPM) was determined in the diet of juvenile red sea bream, Pagrus major. Six isoproteic and isolipidic diets were formulated to replace 0 (control diet), 190, 280, 370, 470 and 560 g of the FM protein kg-1 diet with BPM protein, and referred to as C, BP19, BP28, BP37, BP47 and BP56, respectively. Each diet was fed to triplicate groups of twenty fish (mean weight ~43 g) twice per day to apparent satiation. Fish fed diets C and BP19 did not show significant differences (p >.05) in growth, apparent digestibility or protein and lipid retention efficiency, but the daily feeding rate (DFR) was significantly lower under BP19 than under C. However, almost all growth parameters were significantly reduced when FM protein replacement with BPM was further increased from 280 to 560 g kg-1 diet (p <.05). The results of polynomial regression analysis (second-order) revealed significant negative correlations between dietary copper levels and final mean weight (R2 =.913), specific growth rate (R2 =.913) and DFR (R2 =.956). The results indicated that BPM could replace approximately 190 g of FM protein kg-1 diet in the juvenile red sea bream diet without compromising growth performance or feed efficiency.
• Methanotroph (Methylococcus capsulatus, Bath) bacteria meal as an alternative protein source for Japanese yellowtail, Seriola quinqueradiata

  Amal Biswas; Fumiaki Takakuwa; Shinichi Yamada; Akihisa Matsuda; Renée M. Saville; Allan LeBlanc; Joshua A. Silverman; Nobumitsu Sato; Hideki Tanaka

  Aquaculture 529 735700 - 735700 2020年12月 [査読有り]
  
• Availability of potato protein concentrate as an alternative protein source to fish meal in greater amberjack ( Seriola dumerili ) diets

  Fumiaki Takakuwa; Keinosuke Suzuri; Takao Horikawa; Kunpei Nagahashi; Shinichi Yamada; Amal Biswas; Hideki Tanaka

  Aquaculture Research 51 3 1293 - 1302 2020年03月 [査読有り]
   

  © 2019 John Wiley & Sons Ltd Potato protein concentrate (PPC) is a promising candidate as a fish meal (FM) substitute because it has high protein and essential amino acid content. In the present study, we replaced FM in greater amberjack diets with PPC to investigate the effect on growth and feed utilization. Four isonitrogenous, isolipidic and isocaloric experimental diets were prepared by substituting 0, 20, 40 and 60% of FM protein with PPC (Control, P20, P40 and P60 respectively). The in vitro protein digestibility of protein in PPC was 88.8%, relative to 100% protein in the FM. The in vitro protein digestibility of protein in the experimental diets also decreased with increasing PPC and was lowest at 84.2% in P60. After the 7-week feeding trial, final body weight, weight gain and thermal growth coefficient tended to decrease with increasing PPC and were significantly lower in P60 than in the control (p <.05). Further, fish fed with diets P40 and P60 showed significantly lower feed conversion and protein efficiency ratios than the control group (p <.05). In conclusion, the results suggest that PPC can replace up to 20% of FM in the diet of greater amberjack without compromising the growth performance or feed efficiency.
• Molecular diet analysis of Anguilliformes leptocephalus larvae collected in the western North Pacific

  Seinen Chow; Nobuharu Inaba; Satoshi Nagai; Hiroaki Kurogi; Yoji Nakamura; Takashi Yanagimoto; Hideki Tanaka; Daisuke Hasegawa; Taiga Asakura; Jun Kikuchi; Tsutomu Tomoda; Taketoshi Kodama

  PLOS ONE 14 11 e0225610 - e0225610 2019年11月 [査読有り]
   

  Natural diets of leptocephalus larvae have been enigmatic. In this study, we collected DNA samples from the gut contents and body surface of leptocephali belonging to the five Anguilliform families (Anguillidae, Chlopsidae, Congridae, Muraenidae, and Serrivomeridae) from the northwest Pacific and performed next-generation 18S rDNA sequencing. Wide variety of eukaryotes was detected in both samples, from which eight eukaryotic groups (jellyfish, conoid parasite, tunicate, copepod, krill, segmented worm, fungi, and dinoflagellate) were selected on the basis of abundance. All groups except conoid parasites were common in both the samples. Cnidarian 18S rDNA reads were the most abundant in both the samples; however, the number of samples having cnidarian reads and the read counts were significantly higher in the body surface scraping samples than in the gut content samples, regardless of careful rinsing of the body surface. These results indicate that the cnidarian DNAs are most likely found because of cross contamination from the body surface and/or environment. 18S rDNA read counts of copepod and tunicate in the gut contents were greater than or comparable with those in the body surface scraping samples, which may correspond to the previous observations of fecal pellets and larvacean houses in the leptocephali gut. Thus, the present study supports previous implications that leptocephali utilize detritus materials, so called marine snow.
• Sperm cryopreservation protocols for the large-scale fertilization of Japanese eel using a combination of large-volume straws and low sperm dilution ratio

  野村 和晴; アイバン; 飯尾; 奥田; 風藤 行紀; 田中 秀樹; 太田 博己

  Aquaculture 496 203 - 210 2018年11月 [査読有り]
  
• Observations of gut contents of anguilliform leptocephali collected in the western North Pacific

  Tsutomu Tomoda; Seinen Chow; Hiroaki Kurogi; Makoto Okazaki; Daisuke Ambe; Hirofumi Furuita; Hiroyuki Matsunari; Satoshii Nagai; Kazuki Yokouchi; Shuhei Sawayama; Kazuharu Nomura; Hideki Tanaka; Ryuusuke Sudou; Daisuke Hasegawa; Nobuharu Inaba

  Nippon Suisan Gakkaishi (Japanese Edition) 84 1 32 - 44 2018年 

  The gut contents of anguilliform leptocephali collected by research cruises in the western North Pacific were examined in order to investigate their food sources. Gut contents of 26 leptocephali (Anguillidae, Congridae and Serrivomeridae) examined were amorphous food material containing many small spherical particles. Alcian Blue (AB)-stained aggregates containing spherical particles approximately 2-10 mm in diameter were observed in 14 leptocephali from the 2015 survey, and Coomassie Brilliant Blue (CBB)-stained aggregates containing spherical particles about 2 mm in diameter were observed in 12 leptocephali from the 2016 survey. Red autofluorescence of phytoplankton was exhibited in several sized cells in amorphous food material. Furthermore, polysaccharide-containing transparent exopolymer particles (TEP), proteinaceous Coomassie stainable particles (CSP), and pico/ nano-planktonic particles about 2 mm in diameter were observed in environmental water samples. These results suggest that anguilliform leptocephali utilize phytoplankton-derived particulate organic matter (POM) as one of the food sources. Such feeding ecology makes it possible for anguilliform leptocephali to avoid food competition from predatory, zooplanktivorous and omnivorous fishes that have higher trophic positions in the oligotrophic ocean.
• Genetic parameters and quantitative trait loci analysis associated with body size and timing at metamorphosis into glass eels in captive-bred Japanese eels (Anguilla japonica).

  Kazuharu Nomura; Atushi Fujiwara; Yuki Iwasaki; Issei Nishiki; Aiko Matsuura; Akiyuki Ozaki; Ryusuke Sudo; Hideki Tanaka

  PloS one 13 8 e0201784  2018年 [査読有り]
   

  The Japanese eel (Anguilla japonica) is among the most important aquaculture fish species in Eastern Asia. The present study aimed to identify the genetic parameters underlying body size and the timing at metamorphosis from leptocephali to glass eels in captive-bred Japanese eels, with the intent to foster sustainable development. Larvae from a partly factorial cross (14 sires × 11 dams) were reared until the point of metamorphosis into glass eels. In these organisms, we observed moderate heritability and mild genetic correlations among traits related to body size (h2 = 0.16-0.33) and timing at metamorphosis (h2 = 0.36-0.41). In an F1 full-sib family, quantitative trait loci (QTL) mapping for these traits identified one significant (genome-wide P < 0.05) and five suggestive QTLs (chromosome-wide P < 0.05). These results suggest that in the Japanese eel, metamorphic traits exhibit a polygenic genetic structure comprising many QTLs with small effects. In addition, we updated the genetic linkage map for the Japanese eel and integrated it with our newly constructed de novo genome assembly. The information and tools generated from this study will contribute to the development of freshwater eel genetics and genomics.
• Sperm cryopreservation of Japanese eel, Anguilla japonica

  Chu、浜田; 辻; 奥田; 野村 和晴; 田中 秀樹; 太田 博己

  Aquaculture 473 487 - 492 2017年03月 [査読有り]
  
• Onboard rearing attempts for the Japanese eel leptocephali using POM-enriched water collected in the Western North Pacific

  Seinen Chow; Hiroaki Kurogi; Satoshi Watanabe; Hiroyuki Matsunari; Ryusuke Sudo; Kazuharu Nomura; Hideki Tanaka; Hirofumi Furuita; Atsushi Nishimoto; Masato Higuchi; Tadao Jinbo; Tsutomu Tomoda

  Aquatic Living Resources 30 38 - 38 2017年 [査読有り]
  
• ニホンウナギの種苗生産過程で発現する様々な形態異常

  田中 秀樹

  日本水産学会誌 82 5 800 - 800 2016年10月 [査読有り]
  
• Development of a homologous radioimmunoassay for red seabream follicle stimulating hormone and regulation of gonadotropins by GnRH in red seabream, Pagrus major

  奥沢 公一; 風藤 行紀; 宇治 督; 山口; 田中 秀樹; 入路; 玄 浩一郎

  Gen.Comp. Endocrinol. 239 4 - 12 2016年05月 [査読有り]
  
• ウナギ仔魚はマリンスノーの起源物質を摂取する

  友田 努; 黒木 洋明; 鴨志田 正晃; 今泉 均; 神保 忠雄; 野村 和晴; 古板 博文; 田中 秀樹

  日本水産学会誌 81 4 715 - 721 2015年07月 [査読有り]
  
• Hatchery-reared Japanese eel Anguilla japonica larvae ingest various organic matter formed as part of marine snow

  Tsutomu Tomoda; Hiroaki Kurogi; Masanori Okauchi; Masaaki Kamoshida; Hitoshi Imaizumi; Tadao Jinbo; Kazuharu Nomura; Hirohumi Furuita; Hideki Tanaka

  Nippon Suisan Gakkaishi (Japanese Edition) 81 4 715 - 721 2015年 

  We observed the feeding incidence of Japanese eel Anguilla japonica larvae of 5-28 days post-hatch (dph) using various organic matter formed as part of marine snow. Food organisms such as microalgae (Rhodomonas sp., Isochrysis galbana, Cyclotella sp., and Chaetoceros calcitrans) and appendicularian Oikopleura dioica were raised as the primary food source of marine snow. In algal feeding trials, 10-28 day-old eel larvae ingested algal cells and transparent exopolymer particles (TEP) produced during the exponential growth phase. Furthermore, the feeding incidence of the larvae showed an increasing trend within the range of 40-100% with larval age (dph) and algal cell concentration. In appendicularian feeding trials, 9-day-old eel larvae ingested a larval tadpole body and abandoned house wreckage. The aforementioned gel-like particles were excreted smoothly out of the end of the mid-hind gut during observation. These results indicate that hatchery-reared Japanese eel larvae ingest organic matter formed as part of marine snow as well as natural eel larvae. The gelatinous substances from microalgae and appendicularian may be available as initial food sources for Japanese eel larvae because of their physical properties (buoyancy, suspensibility, absorption, aggregability, and foexibility) in seawater.
• Progression in artificial seedling production of Japanese eel Anguilla japonica

  Tanaka Hideki

  Fisheries science 81 1 11 - 19 Springer Japan 2015年01月 [査読有り][招待有り]
  
• Light-sensitive vertical migration of the Japanese eel Anguilla japonica revealed by real-time tracking and its utilization for geolocation.

  Seinen Chow; Makoto Okazaki; Tomowo Watanabe; Kyohei Segawa; Toshihiro Yamamoto; Hiroaki Kurogi; Hideki Tanaka; Ken-Ichiro Ai; Miho Kawai; Shin-Ichi Yamamoto; Noritaka Mochioka; Ryotaro Manabe; Yoichi Miyake

  PloS one 10 4 e0121801  2015年 [査読有り]
   

  Short-time tracking (one to eight days) of the Japanese eel (Anguilla japonica) using ultrasonic transmitter was performed in the tropical-subtropical area adjacent to the spawning area and temperate area off the Japanese Archipelago. Of 16 eels (11 wild and five farmed) used, 10 wild eels displayed clear diel vertical migration (DVM) from the beginning, while the other five farmed eels tracked for 19 to 66 hours did not. During daytime, a significantly positive correlation between migration depth and light intensity recorded on the vessel was observed in the 10 wild eels, indicating that the eels were sensitive to sunlight even at the middle to lower mesopelagic zone (500 to 800 m). During nighttime, the eel migration depth was observed to be associated with the phase, rising and setting of the moon, indicating that the eels were sensitive to moonlight at the upper mesopelagic zone (<300 m). Two of 10 wild eels were in the yellow stage but shared similar DVM with the silver stage eels. Swimbladders of three silver stage eels were punctured before releasing, but very little effect on DVM was observed. The eels very punctually initiated descent upon nautical dawn and ascent upon sunset, enabling us to determine local times for sunrise and sunset, and hence this behavior may be used for geolocating eels. In fact, estimated positions of eels based on the depth trajectory data were comparable or even better than those obtained by light-based archival tag in other fish species.
• Decreasing dietary lipids improves larval survival and growth of Japanese eel Anguilla japonica

  Hirofumi Furuita; Koji Murashita; Hiroyuki Matsunari; Takeshi Yamamoto; Jiro Nagao; Kazuharu Nomura; Hideki Tanaka

  Fisheries Science 80 3 581 - 587 2014年05月 

  Shark eggs-based diet is the only diet by which eel larvae can grow to glass eels in captivity. However, the high level of lipids in the diet is suggested to negatively affect eel larvae. This paper examines the effect of defatted shark eggs (DSE) and hen egg yolk (HY) on growth and survival of larvae of Japanese eel Anguilla japonica. Lyophilized shark egg and commercial HY were defatted with n-hexane, and four experimental diets were prepared using both defatted and untreated shark eggs and HY. Larvae were reared for 3 weeks by feeding the experimental diets. The highest survival rate was observed in the larvae fed DSE, and larvae fed HY showed the lowest survival rate. The best growth was found in larvae fed DSE, followed by shark eggs and defatted HY, and the worst growth was in HY-fed larvae. These results show that decreasing dietary lipids improves the nutritional value of both shark eggs and HY for eel larvae. Regulation of the dietary lipid level may positively affect the larval performance of eels by combination of ingredients with a low lipid content. © 2014 The Japanese Society of Fisheries Science.
• A ddRAD-based genetic map and its integration with the genome assembly of Japanese eel (Anguilla japonica) provides insights into genome evolution after the teleost-specific genome duplication.

  Wataru Kai; Kazuharu Nomura; Atushi Fujiwara; Yoji Nakamura; Motoshige Yasuike; Nobuhiko Ojima; Tetsuji Masaoka; Akiyuki Ozaki; Yukinori Kazeto; Koichiro Gen; Jiro Nagao; Hideki Tanaka; Takanori Kobayashi; Mitsuru Ototake

  BMC genomics 15 233 - 233 2014年03月 [査読有り]
   

  BACKGROUND: Recent advancements in next-generation sequencing technology have enabled cost-effective sequencing of whole or partial genomes, permitting the discovery and characterization of molecular polymorphisms. Double-digest restriction-site associated DNA sequencing (ddRAD-seq) is a powerful and inexpensive approach to developing numerous single nucleotide polymorphism (SNP) markers and constructing a high-density genetic map. To enrich genomic resources for Japanese eel (Anguilla japonica), we constructed a ddRAD-based genetic map using an Ion Torrent Personal Genome Machine and anchored scaffolds of the current genome assembly to 19 linkage groups of the Japanese eel. Furthermore, we compared the Japanese eel genome with genomes of model fishes to infer the history of genome evolution after the teleost-specific genome duplication. RESULTS: We generated the ddRAD-based linkage map of the Japanese eel, where the maps for female and male spanned 1748.8 cM and 1294.5 cM, respectively, and were arranged into 19 linkage groups. A total of 2,672 SNP markers and 115 Simple Sequence Repeat markers provide anchor points to 1,252 scaffolds covering 151 Mb (13%) of the current genome assembly of the Japanese eel. Comparisons among the Japanese eel, medaka, zebrafish and spotted gar genomes showed highly conserved synteny among teleosts and revealed part of the eight major chromosomal rearrangement events that occurred soon after the teleost-specific genome duplication. CONCLUSIONS: The ddRAD-seq approach combined with the Ion Torrent Personal Genome Machine sequencing allowed us to conduct efficient and flexible SNP genotyping. The integration of the genetic map and the assembled sequence provides a valuable resource for fine mapping and positional cloning of quantitative trait loci associated with economically important traits and for investigating comparative genomics of the Japanese eel.
• Characterization of thyroid hormone receptors during early development of the Japanese eel (Anguilla japonica).

  Yutaka Kawakami; Kazuharu Nomura; Hiromi Ohta; Hideki Tanaka

  General and comparative endocrinology 194 300 - 10 2013年12月 [査読有り]
   

  We studied the profiles of thyroid hormone receptors (TRs) in Japanese eels (Anguilla japonica) during development from hatched larvae to juveniles. Two TRαs (TRαA and TRαB) and one TRβ (TRβA) cDNA clones were generated by RACE. The TRαA, TRαB and TRβA cDNAs encoded 416, 407 and 397 amino acid proteins with much higher homologies to the Japanese conger eel (Conger myriaster) TRs than to other fish TRs. In a transiently transfected Japanese eel cell line, Hepa-E1, the TRs showed thyroid hormone (TH)-dependent activation of transcription from the TH-responsive promoter. Four TR cDNA clones, including TRβB reported in a previous study, were analyzed by real-time RT-PCR. The TR mRNA levels in hatched larvae were determined. The two TRβ mRNAs were present at low levels but there was a peak in the TRαs during the larval stage before metamorphosis. During metamorphosis, the two TRαs both exhibited peaks and expression of the two TRβs was higher than during the early growth stage. This expression pattern is similar to that of the Japanese conger eel. It is possible that thyroid hormones control the early development of Japanese eels and Japanese conger eels through TRs. This is the first analysis of the expression sequence of TRs during early larval stages of Anguilliformes.
• Administration of 17 alpha-hydroxyprogesterone into mature male Japanese eel reduces sperm motility by decreasing potassium ion concentrations in the seminal plasma

  Akira Miura; Kazuharu Nomura; Hitoshi Imaizumi; Tadao Jinbo; Yoshitsugu Masuda; Hideki Tanaka; Hiromi Ohta

  AQUACULTURE 414 217 - 223 2013年11月 [査読有り]
   

  Our objective was to evaluate the effects of hormonal treatments on the milt quality during the induction of spontaneous spawning in male eels. We measured the changes in milt characteristics (sperm motility, milt pH, seminal plasma ionic concentration) during the course of hormonal treatments intended to induce spontaneous spawning, and before and after spawning. Male eels received weekly injections of hCG (1 IU/g BW/wk) to maintain spermiation. To induce spontaneous spawning, males received another priming injection of hCG (1 IU/g BW) two days before spawning, followed 24 h later by an injection of 17 alpha-hydroxyprogesterone (OHP: 1 mu g/g BW). Three males, treated as described above, and one female, that had received hormonal injections to induce vitellogenesis and final maturation, were transferred to a tank to spawn. In Experiment 1, we measured the characteristics of milt (1) before administering the priming dose (1-2 days after the weekly injection of hCG), (2) before injection with OHP, (3) after spawning (24 h after the OHP injection), and (4) before weekly injections with hCG (4-5 days after OHP injection). To evaluate the effects of hormonal treatment on the characteristics of milt we administered the same treatments but did not allow spawning (Experiment 2). In both experiments, the percent motility remained high prior to OHP injection, decreased significantly 24 h after OHP injection, then recovered by the beginning of weekly hCG injection. The changes in potassium ion concentration were similar to those in sperm motility (%) but there was no change in pH and sodium ion concentrations. When the results were analyzed by individual in Experiment 1 (n = 34), the relationship between sperm motility (%) and milt pH showed significant correlations without 24 h after the OHP injection. The relationship between sperm motility (%) and potassium ion concentration showed a highly significant correlation 24 h after the OHP injection. Thus, both pH and potassium ion concentration regulate motility in Japanese eel spermatozoa during hormonal treatment. Furthermore, administration of OHP into spermiating males reduced motility by decreasing the potassium ion concentration in the seminal plasma. (C) 2013 Elsevier B. V. All rights reserved.
• Post-ovulatory oocyte aging induces spontaneous occurrence of polyploids and mosaics in artificial fertilization of Japanese eel, Anguilla japonica

  Kazuharu Nomura; Yukako Takeda; Tatsuya Unuma; Kagayaki Morishima; Hideki Tanaka; Katsutoshi Arai; Hiromi Ohta

  AQUACULTURE 404 15 - 21 2013年08月 [査読有り]
   

  Spontaneous polyploids and mosaics have often been observed in artificially propagated larvae of the Japanese eel, Anguilla japonica. However, the mechanisms responsible for such unusual cytotypes are unclear. In this study, we examined the relationship of such polyploidization and mosaicisms in larvae resulting from artificial propagation to egg quality (fertilization rate and hatching rate) and viability of larvae, and then clarified the inducing factors and the mechanism for occurrence of such phenomena. Eggs stripped from females after induced maturation were artificially inseminated with sperm pre-cultured with artificial seminal plasma. Ploidy was determined by measuring the relative DNA content of the nuclei with flow cytometry. Of 968 embryos from 32 full-sib families, 9.1% were determined to be abnormal, most of which were triploids (86.5% of abnormal embryos); others were haploids (1.1%), aneuploids (2.3%), and mosaics (10.1%). The percentage of normal diploids from each family varied between 56.3% and 100% (90.9 +/- 11.7%, n = 32). A significant positive correlation was found between the fertilization rate (P < 0.001) or the hatching rate (P < 0.001) and the percentage of diploids. Survival rate of triploid eels was similar to diploid eels at 10 days after fertilization whereas aneuploids were inviable. When eggs were left in the body cavity of the female for four hours after ovulation and subsequently fertilized, the percentage of diploids decreased. We tried to elucidate the cause for the occurrence of spontaneous triploids by genetic analysis using 26 microsatellite DNA markers, which have been developed and mapped in relation to the centromere. These results suggest that the occurrence of cytogenetically unusual progeny is associated with over-ripening or aging of ova caused by the lapse of time from ovulation until fertilization, and spontaneous triploid larvae are derived from the duplication of the maternal chromosome set by inhibition of the second polar body release after normal meiosis I (crossing over) in oocyte and fertilization with normal sperm. (C) 2013 The Authors. Published by Elsevier B. V. All rights reserved.
• Partial characterization and ontogenetic development of pancreatic digestive enzymes in Japanese eel Anguilla japonica larvae.

  Koji Murashita; Hirofumi Furuita; Hiroyuki Matsunari; Takeshi Yamamoto; Masahiko Awaji; Kazuharu Nomura; Jiro Nagao; Hideki Tanaka

  Fish physiology and biochemistry 39 4 895 - 905 2013年08月 [査読有り]
   

  The pancreatic digestive enzymes, trypsin, chymotrypsin, lipase and amylase were partially characterized, and changes in their activities were examined during the initial ontogeny of Japanese eel Anguilla japonica larvae from 5 to 34 days post-hatching (dph). The pH optima of the eel larval enzymes were narrower than those other fish species; trypsin activity was highest at pH 9, chymotrypsin and amylase activities were highest at pH 7 and 8, and lipase activity was highest at pH 8 and 9. In an analysis of thermal profiles, the larval pancreatic enzymes had a high optimal temperature and high thermal stability, which are typical of fish from the tropics. At 12 and 13 dph, lipase activity and gene expression levels of trypsin (-a and -b), lipase and amylase decreased markedly, suggesting a marked change in larval metabolism at that time. These data could be useful in the development of artificial larval diets in Japanese eel.
• Determination of periods of sensitivity to low-salinity and low-temperature conditions during the early development of cultured Japanese eel Anguilla japonica larvae with respect to the rate of morphological deformity at completion of yolk resorption

  Tadahide Kurokawa; Hideyuki Shibahara; Koichiro Gen; Kazuharu Nomura; Hideki Tanaka

  Fisheries Science 79 4 673 - 680 2013年07月 

  The present study analyzed the rate of occurrence of deformities at completion of yolk resorption after Japanese eel larvae were exposed to low-salinity (29 psu) or low-water-temperature (20 °C) conditions (after they had been reared under suitable conditions: 34 psu, 25 °C) at various points between 0 and 8 days post-fertilization (dpf) in order to determine the period of sensitivity of the larvae to low-salinity or low-temperature conditions. No significant differences were observed between the rate of deformed larvae obtained in the groups reared under suitable conditions and the corresponding rates in groups that were exposed to low-salinity or low-temperature conditions at 4 dpf or later, but the frequency of normal larvae showed a downward trend in experimental groups that were subjected to low-salinity or low-temperature conditions at 3 dpf or earlier. Occurrence rates of pericardial edema were significantly higher in experimental groups that were exposed to low-salinity or low-temperature conditions at 2 dpf or earlier. Therefore, it was concluded that the rearing conditions for Japanese eel larvae should be maintained at 34 psu salinity and 25 °C until at least 4 dpf in order to reduce the occurrence of larval deformity at completion of yolk resorption. © 2013 The Japanese Society of Fisheries Science.
• Optimum temperature of rearing water during artificial induction of ovulation in Japanese eel

  Tatsuya Unuma; Sayumi Sawaguchi; Natsuki Hasegawa; Noriko Tsuda; Toshiomi Tanaka; Kazuharu Nomura; Hideki Tanaka

  AQUACULTURE 358 216 - 223 2012年08月 [査読有り]
   

  To obtain fertilized eggs of the Japanese eel Anguilla japonica, mature females are injected with maturation-inducing steroid (MIS) to induce final oocyte maturation and ovulation and then paired with mature males for spawning (induced spawning method) or stripped to collect eggs for insemination (stripping and insemination method). Progress of final oocyte maturation and ovulation and consequent egg quality are affected by the environmental water temperature. To detect the optimum temperature of the rearing water during artificial induction of ovulation by MIS injection, we investigated the effects of water temperature on ovulation, egg quality, and its deterioration due to over-ripening using the stripping and insemination method. Mature females injected with 17 alpha-hydroxyprogesterone were stocked in tanks maintained at 17.5 degrees C, 20 degrees C, 22.5 degrees C or 25 degrees C. Earlier ovulation occurred at the higher water temperatures. Viability of the eggs that were collected from females immediately after observation of ovulation was similar at 20 degrees C and 22.5 degrees C but inferior at 17.5 degrees C and 25 degrees C. After eggs are retained in the body cavity for an hour, their viability was increasingly reduced due to over-ripening at the higher temperatures between 20 degrees C and 25 degrees C. Moreover, hatchability of unfertilized eggs placed in tubes and maintained at 15 degrees C, 17.5 degrees C, 20 degrees C, 22.5 degrees C or 25 degrees C for 3 h showed a time-dependent decrease due to over-ripening, which progressed slower at the lower temperature band between 20 degrees C and 25 degrees C. However, 15 degrees C and 17.5 degrees C did not delay the progress of over-ripening compared to 20 degrees C. We conclude that 17.5 degrees C and 25 degrees C are not appropriate for ovulation induction, because egg quality just after ovulation is lower than at 20 degrees C and 22.5 degrees C. In the stripping and insemination method, 22.5 degrees C is disadvantageous compared to 20 degrees C because of the faster progress of over-ripening, though this does not matter in the induced spawning method as spawning behavior and consequent fertilization are expected to occur at an appropriate timing after ovulation. (C) 2012 Elsevier B.V. All rights reserved.
• 西マリアナ海嶺南部海域において初めて捕獲された産卵後のウナギ Anguilla japonica 雌個体

  黒木 洋明; 岡崎 誠; 望岡 典隆; 神保 忠雄; 橋本 博; 高橋 正知; 田和 篤史; 青山 潤; 篠田 章; 塚本 勝巳; 田中 秀樹; 玄 浩一郎; 風藤 行紀; 張 成年

  日本水産學會誌 = Bulletin of the Japanese Society of Scientific Fisheries 78 4 655 - 655 The Japanese Society of Fisheries Science 2012年07月
• Fusion of lipid droplets in Japanese eel oocytes: Stage classification and its use as a biomarker for induction of final oocyte maturation and ovulation

  Tatsuya Unuma; Natsuki Hasegawa; Sayumi Sawaguchi; Toshiomi Tanaka; Takahiro Matsubara; Kazuharu Nomura; Hideki Tanaka

  AQUACULTURE 322 142 - 148 2011年12月 [査読有り]
   

  The quality of eggs obtained from maturation-induced Japanese eel, Anguilla japonica, is unstable. One of the causes for low quality eggs is that females are artificially induced to ovulate at an inappropriate maturational status. Here we investigated the feasibility to use the morphological changes of lipid droplets in oocytes as a biomarker to show the optimum timing for injections of salmon pituitary extract (SPE) for priming and maturation-inducing steroid (MIS) for final oocyte maturation and ovulation. Various sizes of oocytes (700 to 1000 mu m) were collected by cannulation from maturation-induced female eels during five days until ovulation. Morphology of the lipid droplets in these oocytes were classified into 10 stages mainly on the basis of their diameter, which increased with the progress of maturation as the droplets fused together. To assess the maturational status of each female, the lipid droplet stage was determined for 10 oocytes randomly chosen among the most advanced mode of developing oocytes and the median value was defined as the stage for the individual. Relationship between the lipid droplet stage at induction of ovulation and hatchability of the ovulated eggs was examined in 23 females, in which the hatching rate markedly fluctuated. Stages of females from which good quality eggs were obtained converged around stage 4 (five largest droplets, 55 to 70 mu m) at priming with SPE, stage 6 (90 to 110 mu m) at injection with MIS, and stage 7 (110 to 130 mu m) at ovulation, while those of females from which low quality eggs were obtained showed distributions over broader ranges. Furthermore, 466 females were induced to mature and the lipid droplet stage at induction of ovulation was examined in 13 females from which high quality eggs (hatching rate >80%) were obtained. Most of the 13 females were at stage 3 (40 to 55 mu m) or 4 when primed with SPE, at stage 6 when injected with MIS, and at stage 7 when they ovulated. These results suggest that the optimum stages for SPE priming, MIS injection, and ovulation are stages 3 to 4, 6, and 7, respectively, though the optimum stage for priming will be variable if the temperature and/or the time between priming and MIS injection is varied. We conclude that the lipid droplet stage can be used as a sensitive biomarker to show the optimum timing for inducing ovulation by hormonal treatments. (C) 2011 Elsevier B. V. All rights reserved.
• Distribution of pepsinogen- and ghrelin-producing cells in the digestive tract of Japanese eel (Anguilla japonica) during metamorphosis and the adult stage.

  Tadahide Kurokawa; Miei Koshio; Hiroyuki Kaiya; Hiroshi Hashimoto; Kazuharu Nomura; Susumu Uji; Masahiko Awaji; Koichiro Gen; Hideki Tanaka

  General and comparative endocrinology 173 3 475 - 82 2011年09月 [査読有り]
   

  Pepsinogen is the precursor form of the gastric-specific digestive enzyme, pepsin. Ghrelin is a representative gastric hormone with multiple functions in vertebrates, including the regulation of growth hormone release, stimulation of food intake and gastrointestinal motility function. We investigated chronological changes in the distribution of pepsinogen-expressing cells by in situ hybridization and ghrelin-immunoreactive cells by immunohistochemistry in the Japanese eel (Anguilla japonica) during metamorphosis from the leptocephalus sage to the elver stage. The ghrelin-producing cells first appeared in the gastric cecum and pyloric portion of the stomach in the late phase of metamorphosing leptocephali, whereas the pepsinogen-producing cells were first detected in the early phase of the glass-eel stage. These suggest that endocrine cells differentiated earlier than exocrine cells in the eel stomach. Accompanying eel development, the distribution of ghrelin-producing cells spread to the esophagus and other regions of the stomach, but not to the intestine. These results may be related to the changes in dietary habits during metamorphosis in the Japanese eel.
• First capture of post-spawning female of the Japanese eel Anguilla japonica at the southern West Mariana Ridge

  Hiroaki Kurogi; Makoto Okazaki; Noritaka Mochioka; Tadao Jinbo; Hiroshi Hashimoto; Masanori Takahashi; Atsushi Tawa; Jun Aoyama; Akira Shinoda; Katsumi Tsukamoto; Hideki Tanaka; Koichiro Gen; Yukinori Kazeto; Seinen Chow

  FISHERIES SCIENCE 77 2 199 - 205 2011年03月 [査読有り]
   

  Two adult male freshwater eels, Anguilla japonica, were captured in June 2008 in the West Mariana Ridge (13A degrees N, 142A degrees E) in the North Pacific, but collections of females have yet to be reported. In September 2008, we successfully caught two adult female A. japonica, 55.5 and 66.2 cm in total length, in the adjacent but northern area (14A degrees N, 143A degrees E). Six newly hatched eel larvae (pre-leptocephali) were also collected by subsequent plankton sampling conducted near the female catch area. Female adults appeared to be in the post-spawning state, probably a considerable time after spawning, since a small number of remarkably regressed oocytes (50-250 mu m in diameter) were observed in the ovaries. Capture of post-spawning female eels and newly hatched larvae near the Suruga Seamount (14A degrees N) together with the previous collection of mature males in the southern area (13A degrees N) corroborates that the area along the West Mariana Ridge is the spawning area of this species, but suggests that the eel spawning may occur over a wider area than previously expected.
• Oceanic spawning ecology of freshwater eels in the western North Pacific.

  Katsumi Tsukamoto; Seinen Chow; Tsuguo Otake; Hiroaki Kurogi; Noritaka Mochioka; Michael J Miller; Jun Aoyama; Shingo Kimura; Shun Watanabe; Tatsuki Yoshinaga; Akira Shinoda; Mari Kuroki; Machiko Oya; Tomowo Watanabe; Kazuhiro Hata; Shigeho Ijiri; Yukinori Kazeto; Kazuharu Nomura; Hideki Tanaka

  Nature communications 2 179 - 179 2011年02月 

  The natural reproductive ecology of freshwater eels remained a mystery even after some of their offshore spawning areas were discovered approximately 100 years ago. In this study, we investigate the spawning ecology of freshwater eels for the first time using collections of eggs, larvae and spawning-condition adults of two species in their shared spawning area in the Pacific. Ovaries of female Japanese eel and giant mottled eel adults were polycyclic, suggesting that freshwater eels can spawn more than once during a spawning season. The first collection of Japanese eel eggs near the West Mariana Ridge where adults and newly hatched larvae were also caught shows that spawning occurs during new moon periods throughout the spawning season. The depths where adults and newly hatched larvae were captured indicate that spawning occurs in shallower layers of 150-200 m and not at great depths. This type of spawning may reduce predation and facilitate reproductive success.
• A genetic linkage map of the Japanese eel (Anguilla japonica) based on AFLP and microsatellite markers

  Kazuharu Nomura; Akiyuki Ozaki; Kagayaki Morishima; Yukio Yoshikawa; Hideki Tanaka; Tatsuya Unuma; Hiromi Ohta; Katsutoshi Arai

  AQUACULTURE 310 3-4 329 - 342 2011年01月 [査読有り]
   

  The first genetic linkage map of the Japanese eel (Anguilla japonica) was constructed based upon Amplified Fragment Length Polymorphism (AFLP) and microsatellite (STR) markers with an F-1 pseudo-testcross strategy. The segregation of 106 microsatellite loci, which included 74 newly developed, and 463 polymorphic loci identified from 56 AFLP primer combinations was studied in 46 F-1 individuals derived from a single female and a male. A total of 319 markers (99 STRs + 220 AFLP) are placed on the female map and 314 markers (91 STRs + 223 AFLP) on the male map. The female map spans 1732.4 cM (Kosambi) in 22 linkage groups with an average spacing of 7.2 cM; the male map spans 964.9 cM in 22 linkage groups with an average spacing of 6.3 cM. The average ratio of male:female recombination rates was 1:2.11. The estimated coverage of the genome was 82.4% for the female map and 74.0% for the male map. This map is the first linkage map in the order Anguilliformes and provides a basis for mapping quantitative trait loci (QTL) and for breeding applications. (C) 2010 Elsevier B.V. All rights reserved.
• The mechanism for primordial germ-cell migration is conserved between Japanese eel and zebrafish.

  Taiju Saito; Rie Goto-Kazeto; Yutaka Kawakami; Kazuharu Nomura; Hideki Tanaka; Shinji Adachi; Katsutoshi Arai; Etsuro Yamaha

  PloS one 6 9 e24460  2011年 [査読有り]
   

  Primordial germ cells (PGCs) are segregated and specified from somatic cells during early development. These cells arise elsewhere and have to migrate across the embryo to reach developing gonadal precursors. Several molecules associated with PGC migration (i.e. dead-end, nanos1, and cxcr4) are highly conserved across phylum boundaries. However, since cell migration is a complicated process that is regulated spatially and temporally by multiple adaptors and signal effectors, the process is unlikely to be explained by these known genes only. Indeed, it has been shown that there are variations in PGC migration pattern during development among teleost species. However, it is still unclear whether the actual mechanism of PGC migration is conserved among species. In this study, we studied the migration of PGCs in Japanese eel (Anguilla japonica) embryos and tested the migration mechanism between Japanese eel and zebrafish (Danio rerio) for conservation, by transplanting eel PGCs into zebrafish embryos. The experiments showed that eel PGCs can migrate toward the gonadal region of zebrafish embryos along with endogenous PGCs, even though the migration patterns, behaviors, and settlements of PGCs are somewhat different between these species. Our results demonstrate that the migration mechanism of PGCs during embryonic development is highly conserved between these two distantly related species (belonging to different teleost orders).
• Efficiency of peptide nucleic acid-directed PCR clamping and its application in the investigation of natural diets of the Japanese eel leptocephali.

  Takeshi Terahara; Seinen Chow; Hiroaki Kurogi; Sun-Hee Lee; Katsumi Tsukamoto; Noritaka Mochioka; Hideki Tanaka; Haruko Takeyama

  PloS one 6 11 e25715  2011年 [査読有り]
   

  Polymerase chain reaction (PCR)-clamping using blocking primer and DNA-analogs, such as peptide nucleotide acid (PNA), may be used to selectively amplify target DNA for molecular diet analysis. We investigated PCR-clamping efficiency by studying PNA position and mismatch with complementary DNA by designing PNAs at five different positions on the nuclear rDNA internal transcribed spacer 1 of the Japanese eel Anguilla japonica in association with intra-specific nucleotide substitutions. All five PNAs were observed to efficiently inhibit amplification of a fully complementary DNA template. One mismatch between PNA and template DNA inhibited amplification of the template DNA, while two or more mismatches did not. DNA samples extracted from dorsal muscle and intestine of eight wild-caught leptochephalus larvae were subjected to this analysis, followed by cloning, nucleotide sequence analysis, and database homology search. Among 12 sequence types obtained from the intestine sample, six were identified as fungi. No sequence similarities were found in the database for the remaining six types, which were not related to one another. These results, in conjunction with our laboratory observations on larval feeding, suggest that eel leptocephali may not be dependent upon living plankton for their food source.
• A close relationship between androgen levels and eumelanogenesis in the teleost red seabream (Pagrus major): Quantitative analysis of its seasonal variation and effects of oral treatment with methyl-testosterone

  Kohsuke Adachi; Kazumasa Wakamatsu; Shosuke Ito; Hajime Matsubara; Kazuharu Nomura; Hideki Tanaka; Keitaro Kato

  COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY 156 2 184 - 189 2010年06月 [査読有り]
   

  Male and female teleost seabream (Pagrus major) were examined for seasonal variation of eumelanin, pheomelanin, 11-ketotestosterone (11KT, fish androgen), lightness (L* value) and Gonad Somatic index (GSI: gonad mass/body mass x 100). In males, levels of pyrrole-2,3,5-tricarboxylic acid (a marker of eumelanin), 11KT and the GSI increased sharply from September and plateaued in March and April when the fish are sexually mature. These results are consistent with the lightness of their body color. Using the data from males, a high correlation was observed for all combinations of those four variables (PTCA, 11CT, lightness and GSI). In females, little change was observed in those variables except for the GSI. 4-Amino-3-hydroxyphenylalanine (a marker of pheomelanin) was also analyzed, but it was below the detection limit at all times. Oral treatment of juvenile red seabream with synthetic androgen methyl-testosterone for 2 months induced eumelanin accumulation about 3 times higher than the control. These data show that there is a close relationship between androgen levels and eumelanin accumulation in teleosts. This is the first report that androgen affects melanin accumulation in a dose-dependent manner. (C) 2010 Elsevier Inc. All rights reserved.
• ニホンウナギとヨーロッパウナギのハイブリッドは成長できるか?

  松原 創; 野村 和晴; 村下 幸司; 黒川 忠英; 小林 亨; 田中 秀樹

  比較内分泌学 = Comparative endocrinology 36 137 133 - 139 Japan Society for Comparative Endocrinology 2010年05月
• Japanese eel Anguilla japonica do not assimilate nutrition during the oceanic spawning migration: Evidence from stable isotope analysis

  Seinen Chow; Hiroaki Kurogi; Satoshi Katayama; Daisuke Ambe; Makoto Okazaki; Tomowo Watanabe; Tadafumi Ichikawa; Masashi Kodama; Jun Aoyama; Akira Shinoda; Shun Watanabe; Katsumi Tsukamoto; Sachie Miyazaki; Shingo Kimura; Yoshiaki Yamada; Kazuharu Nomura; Hideki Tanaka; Yukinori Kazeto; Kazuhiro Hata; Takeshi Handa; Atsushi Tawa; Noritaka Mochioka

  Marine Ecology Progress Series 402 233 - 238 2010年03月 

  During 2008 and 2009, a total of 12 adult Japanese eels Anguilla japonica were captured in the southern part of the West Mariana Ridge, the presumed spawning area. We compared the stable carbon and nitrogen isotope ratios (δ13C and δ15N) between the 'Mariana silvers' (terminal phase) and those of yellow and silver eels caught in rivers, lakes and coastal areas of Japan (initial phase). Profiles of stable isotope signatures between the initial and terminal phases were similar; both characteristically had a wide range for δ13C (-24.9 to -12.0% and -20.5 to -11.3% for the initial and terminal phases, respectively) and δ15N (6.5 to 18.4% and 9.0 to 18.1, respectively). Mesopelagic fishes, including several other anguillid species caught near the West Mariana Ridge, characteristically had a very narrow range of δ13C (-16.9 to -15.3%) and a wide but lower range of δ15N (5.3 to 11.1%) than the Japanese eels. The very similar profiles in stable isotopic signatures between the initial and terminal phase eels, distinct from those of Mariana mesopelagic fishes, indicate that Japanese eels do not assimilate nutrition from the marine environment during long (ca. 6 mo) spawning migration and retain the initial isotopic values of where they ceased feeding. © Inter-Research 2010, www.int-res.com.
• Trypsin is a multifunctional factor in spermatogenesis

  Chiemi Miura; Takashi Ohta; Yuichi Ozaki; Hideki Tanaka; Takeshi Miura

  PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 106 49 20972 - 20977 2009年12月 [査読有り]
   

  Trypsin is well known as a pancreatic enzyme that is typically secreted into the intestine to digest proteins. We show in our current study, however, that trypsin is also a key factor in the control of spermatogenesis. A progestin in teleost fish, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (DHP), is an essential component of the spermatogenesis pathway, particularly during the initiation of the first meiotic division. In the course of our investigations into the mechanisms underlying progestin-stimulated spermatogenesis, we identified that eel trypsinogen is upregulated in eel testis by DHP treatment. Trypsinogen is expressed in the Sertoli cells surrounding spermatogonia and in the membranes of spermatids and spermatozoa. Using an in vitro eel testicular culture system, we further analyzed the roles of trypsin in spermatogenesis. The inhibition of trypsin using specific antibodies or serine protease inhibitors was found to compromise DHP-induced spermatogenesis. A low dose of trypsin induces DNA synthesis and the expression of Spo11, a molecular marker of meiosis, in germ cells. By comparison, a higher dose of trypsin partially induced spermiogenesis. Furthermore, trypsin was detectable in the membranes of the spermatozoa and found to be associated with fertilization in fish. Our results thus demonstrate that trypsin and/or a trypsin-like protease is an essential and multifunctional factor in spermatogenesis.
• Influence of salinity on morphological deformities in cultured larvae of Japanese eel, Anguilla japonica, at completion of yolk resorption

  Takuma Okamoto; Tadahide Kurokawa; Koichiro Gen; Koji Murashita; Kazuharu Nomura; Shin Kwon Kim; Hajime Matsubara; Hiromi Ohta; Hideki Tanaka

  Aquaculture 293 1-2 113 - 118 2009年08月 

  The occurrence of morphological deformities under different incubation salinities (24, 30, 33, 36 and 42 practical salinity units [psu]) was examined in Japanese eel larvae. Fertilized eggs hatched at all salinity treatments. The survival rate until yolk resorption decreased at higher than 36 psu. The proportions of deformed larvae reared at 36 psu were significantly lower than at other treatments. Pericardial edema and abnormal lower jaw increased at lower than 33 psu and spinal curvature occurred at high salinity (42 psu). In contrast, the incubation salinity did not significantly affect the relative frequency of abnormal neurocranium. These results imply that the optimal salinities for rearing Japanese eel eggs and embryos are 34-35 psu from the viewpoints of survival and deformity. Taken together with previous study [Kurokawa, T., Okamoto, T., Gen, K., Uji, S., Murashita, K., Unuma, T., Nomura, K., Matsubara, H., Kim, H.S., Ohta, H., Tanaka, H., in press. Influence of Water Temperature on Morphological Deformities in Cultured Larvae of Japanese Eel, Anguilla japonica, at Completion of Yolk Resorption. J. World Aqua. Soc.], the rearing of eel eggs and embryos at 25 °C and 34-35 psu probably decreases the mortality and deformity rate of eel larvae at yolk resorption stage. © 2009 Elsevier B.V. All rights reserved.
• Vitamin contents of eggs that produce larvae showing a high survival rate in the Japanese eel Anguilla japonica

  Hirofumi Furuita; Tatsuya Unuma; Kazuharu Nomura; Hideki Tanaka; Tsuyoshi Sugita; Takeshi Yamamoto

  AQUACULTURE RESEARCH 40 11 1270 - 1278 2009年07月 

  This paper describes the relationship between the egg vitamin concentrations and the egg quality in the Japanese eel Anguilla japonica. No notable relation was found between any vitamin and the fertilization rate. Hatching and survival rates of larvae, however, significantly increased with an elevated level of egg vitamin C (VC). In contrast to VC, the relation between vitamins E (VE) and A (VA) concentrations and survival rate showed a clear peak, with a reduced survival rate at both higher and lower vitamin concentrations. The ratio of VE to lipid or highly unsaturated fatty acid (HUFA) in eggs positively correlated with hatching and survival rates of larvae. High-quality (HQ) eggs were determined as eggs that produced larvae having a survival rate higher than 80% at 8 days post hatch, and low-quality (LQ) eggs were determined as eggs that did not hatch. The level of VC of HQ was significantly higher than LQ. The results of this study suggest that HQ eggs, which produce larvae having a high survival rate, must have high levels of VC and VE/HUFA ratio and contain optimum levels of VA and VE in Japanese eel.
• Positive buoyancy in eel leptocephali: an adaptation for life in the ocean surface layer

  Katsumi Tsukamoto; Yoshiaki Yamada; Akihiro Okamura; Toyoji Kaneko; Hideki Tanaka; Michael J. Miller; Noriyuki Horie; Naomi Mikawa; Tomoko Utoh; Satoru Tanaka

  MARINE BIOLOGY 156 5 835 - 846 2009年04月 [査読有り]
   

  Many planktonic organisms have adaptations such as floats or lighter substances to obtain buoyancy to help them remain in the surface layer of the ocean where photosynthetic primary production occurs and food is most abundant. The almost totally transparent eel larvae, called leptocephali, are a unique member of the planktonic community of the surface layer, but their ecology and physiology are poorly understood. We conducted a comparative study on the specific gravity of planktonic animals including 25 taxa of 7 phyla of marine invertebrates and 6 taxa of leptocephali (vertebrate) to gain a broad perspective on the buoyancy of the eggs and larval stages of the Japanese eel. The specific gravity values of the various freshly caught marine invertebrate taxa varied widely from 1.020 to 1.425, but leptocephali had some of the lowest values (1.028-1.043). Artificially cultured live leptocephali had even greater buoyancies with specific gravities of 1.019-1.025 that were close to or lower than seawater, and their buoyancy showed ontogenetic changes among the different early life history stages. Leptocephali appear to have a unique mechanism of buoyancy control by chloride cells all over body surface through osmoregulation of body fluid contained in the extracellular matrix of transparent gelatinous glycosaminoglycans filling their bodies. This adaptation is likely a key factor for their survival by helping them to remain in the surface layer where food particles are the most abundant, while being transparent for predator avoidance. The ontogenetic change in buoyancy of eel eggs, leptocephali and glass eels likely enhances their larval survival, transport, and recruitment to terrestrial freshwater habitats.
• Occurrence of spontaneously spermiating eels in captivity

  Hajime Matsubara; Hideki Tanaka; Kazuharu Nomura; Tohru Kobayashi; Koji Murashita; Tadahide Kurokawa; Tatsuya Unuma; Shin Kwon Kim; Mark P. Lokman; Takahiro Matsubara; Hirohiko Kagawa; Hiromi Ohta

  Cybium 32 2 SUPPL. 174 - 175 2008年07月 

  Two spontaneously spermiating Japanese eels, Anguilla japónica, one reared in fresh water and the other in seawater were identified. The gonads of these eels revealed male germ cells in all stages of development, as well as a large number of oil droplet or early vitellogenic oocytes. Sperm from seawater reared fish had fertilizing capability as reflected in the production of hatched larvae. The larvae grew normally and some of them underwent metamorphosis into glass eel. Albeit rare, we have shown that eel under cultivation conditions could mature naturally and produce milt with fertilizing ability.
• The role of trypsin-like protease in sperm on fertilization in fish

  Takashi Ohta; Chiemi Miura; Yosuke Shimizu; Kaori Mizuno; Hajime Matsubara; Hideki Tanaka; Takeshi Miura

  CYBIUM 32 2 166 - 166 2008年07月 

  Fertilization is an important process for the continuance of the species. In most of fish species, sperm fuses with an ovum through micropyle on the egg chorion because sperm does not have acrosome. In Japanese eel (Anguilla japonica), however, trypsin, a member of the serine protease family, is expressed in their testis by stimulation of 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (DHP), which induces the initiation of meiosis, spermiation and sperm maturation in spermatogenesis. In this study, we investigated whether the trypsin-like protease exists in sperm in eel and kelp bass (Epinephelus bruneus Bloch) and it acts on fertilization in fish using sperm and eggs of both fishes. Tryptic activity was detected in the solubilized sperm membrane protein in both fishes. Using sperm of both fishes, treated with serine protease inhibitors or anti-eel trypsin antibody, artificial fertilization was performed. As a result, treatment with serine protease inhibitors or anti-eel trypsin antibody significantly decreased the fertilization rates in both fishes. These results suggest that trypsin-like protease exists in sperm membrane and plays an important role in fertilization of fish whose sperm does not have acrosome.
• Influence of water temperature on morphological deformities in cultured larvae of Japanese Eel, Anguilla japonica, at Completion of Yolk Resorption

  Tadahide Kurokawa; Takuma Okamoto; Koichiro Gen; Susumu Uji; Koji Murashita; Tatsuya Unuma; Kazuharu Nomura; Hajime Matsubara; Shin Kwon Kim; Hiromi Ohta; Hideki Tanaka

  Journal of the World Aquaculture Society 39 6 726 - 735 2008年 

  The occurrence of morphological deformities under different rearing water temperatures (18, 20, 22, 24, 26, 28, and 30C) was examined in Japanese eel larvae. The rates of hatching and survival until yolk resorption at 22-26C were higher than those at other water temperatures. Fertilized eggs never hatched at 18 and 30C. The rates of occurrence of abnormal larvae reared at the water temperatures 24-28C were lower than those at 20 or 22C. Pericardial edema and lower jaw deformities occurred most frequently at lower temperatures (20 and 22C). In contrast, the incubation temperature did not significantly affect the relative frequency of some neurocranial deformities and of spinal curvature. These results imply that the optimal temperatures for rearing Japanese eel eggs and embryos are 24-26C from the viewpoints of survival and deformity. © Copyright by the World Aquaculture Society 2008.
• Development of thyroid gland and changes in thyroid hormone levels in Leptocephali of Japanese Eel (Anguilla japonica)

  Keisuke Yamano; Kazuharu Nomura; Hideki Tanaka

  AQUACULTURE 270 1-4 499 - 504 2007年09月 [査読有り]
   

  Development of the thyroid gland of the Japanese eel (Anguilla japonica) was studied with the use of tank-reared fish. A single thyroid follicle was first found in larvae at 29 days post hatching (dph), total length (TL) 12 mm. Until reaching 25 mm in TL (100 dph), leptocephali had one or two follicles per individual. The inner colloid of the follicles was weakly immuno-positive against the anti-thyroxine (T-4) antibody. The number of thyroid follicles and the immunoreactivity later increased as the larvae grew. Thyroid hormones (TH) T-4 and triiodothyronine (T-3) were not detected in premetamorphic larvae by radioimmunoassays, but became detectable during metamorphosis. The maximum level of T-4 was seen in fish at the end of metamorphosis and in just-metamorphosed juveniles, whereas T-3 reached the highest level during metamorphosis and declined toward the end of metamorphosis. The results indicated that the thyroid gland first became active during metamorphosis in the development of eel. (C) 2007 Elsevier B.V. All rights reserved.
• Lipid and fatty acid composition of eggs producing larvae with high survival rate in the Japanese eel

  H. Furuita; T. Unuma; K. Nomura; H. Tanaka; K. Okuzawa; T. Sugita; T. Yamamoto

  JOURNAL OF FISH BIOLOGY 69 4 1178 - 1189 2006年10月 [査読有り]
   

  Eggs of Japanese eel Anguilla japonica were obtained by artificial induction of maturation. Fertilization and hatching rates, and survival rates of normal larvae were examined. The levels of total lipids and polar lipids (PL) of high quality (HQ; > 80% survival rate at 8 days post-hatch) eggs were significantly lower than low quality (LQ; hatching and survival rates were zero) eggs. The docosahexaenoic acid (DHA) level in PL of HQ eggs, however, was significantly higher than in LQ eggs. In contrast to DHA, arachidonic acid level was negatively correlated with egg quality variables and it was lower in HQ than in LQ eggs. Most of the egg lipid and fatty acid components showed larger variation in LQ than in HQ eggs. (c) 2006 The Authors Journal compilation (c) 2006 The Fisheries Society of the British Isles.
• Expression of growth hormone family and growth hormone receptor during early development in the Japanese eel (Anguilla japonica).

  Yuichi Ozaki; Haruhisa Fukada; Hideki Tanaka; Hirohiko Kagawa; Hiromi Ohta; Shinji Adachi; Akihiko Hara; Kohei Yamauchi

  Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology 145 1 27 - 34 2006年09月 [査読有り]
   

  In a previous study, we identified cDNAs encoding the growth hormone receptor (eGHR1) and eGHR1 homologue (eGHR2) in Japanese eel (Anguilla japonica). In the present study, changes in the developmental expression of growth hormone (GH), eGHR1 and eGHR2 were investigated in the Japanese eel eggs and preleptocephali by RT-PCR and immunohistochemical methods in an attempt to examine the involvement of these proteins in larval growth. The GH transcripts and the production of GH protein were not detected in the newly hatched larvae and preleptocephali at day 3 post-hatch, however, these were detected at day 6 post-hatch, and also detected at higher levels at day 10 post-hatch. In contrast, prolactin and somatolactin transcripts could not be detected in all preleptocephalus specimens (newly hatched larvae and preleptocephali at day 3, 6 and 10 post-hatch). eGHR1 and eGHR2 transcripts were detected in all preleptocephalus specimens. Therefore, it is plausible that the actions of GH during the preleptocephalus stage are mediated through the eGHRs. The present data suggest that GHR-mediated actions of GH begin at the same time as the initiation of GH production, and that GH plays important roles in larval growth and survival to the leptocephalus stage. eGHR1 mRNA, which is thought to be of maternal origin, was also detected in ovulated eggs. However, the role of eGHR1 mRNA in eggs is not clear.
• Microsatellite-centromere mapping in the Japanese eel (Anguilla japonica) by half-tetrad analysis using induced triploid families

  Nomura Kazuhara; Morishima Kagayaki; Tanaka Hideki; Unuma Tatsuya; Okuzawa Koichi; Ohta hiromi; Arai Katsutoshi

  Aquaculture 257 1 53 - 67 Elsevier 2006年06月 

  Genetic improvement of the Japanese eel (Anguilla japonica) can be achieved by artificially controlling its life cycle using recent advances in reproductive biology. In this study, we developed 43 microsatellite loci to confirm Mendelian inheritance at 10 of them as well at 16 previously reported in two full-sib families produced by artificial insemination. In order to establish a base for aquaculture genetics of this species in the near future, these microsatellite loci were mapped in relation to the centromere by half-tetrad analysis using four artificially induced triploid families. The second division segregation frequency (y) of the microsatellite loci ranged from 0.008 to 0.968 (mean ± SD = 0.645 ± 0.298). These results suggest the presence of strong chiasma interference in the eel. Significant differences were observed for the map distances of microsatellite loci between the two isolation procedures. Microsatellites isolated using the enrichment procedure were mapped to various sites starting from the centromere to the telomere, whereas those from the conventional size-selected library showed a tendency to be distributed in the telomeric region.
• Fine structure and differentiation of the alimentary canal in captive-bred Japanese eel Anguilla japonica preleptocephali

  Yuichi Ozaki; Hideki Tanaka; Hirohiko Kagawa; Hiromi Ohta; Shinji Adachi; Kohei Yamauchi

  Fisheries Science 72 1 13 - 19 2006年02月 

  The fine structure of the alimentary canal in preleptocephali produced by artificially matured Japanese eel was examined. At 1 day posthatch (dph), the alimentary canal was found only above the dorsal side of the yolk mass, and the epithelium was composed of a single layer of epithelial cells. By 5 dph, the alimentary canal was divided into three segments based on the structure of the epithelial cells: foregut, midgut and hindgut, corresponding to the future esophagus, intestine and rectum, respectively. After 7 dph, the epithelium in the foregut was surrounded by a circular muscle layer, suggesting a role in the transportation of food materials. The epithelial cells of the midgut exhibited well-developed membranous structures, which are deduced to be invaginations of the cytoplasmic membrane. Pinocytotic invaginations and vacuoles were observed in the epithelial cells of the hindgut; this observation suggests that this region is involved in the uptake of food. Significant changes in morphological features of the epithelial cells in each segment were observed until 7 dph; however, these were not evident between 7 dph and 13 dph. Consequently, the differentiation of the alimentary canal was completed by 7 dph, and preleptocephalus had developed the ability to absorb food by 7 dph.
• Microsatellite genotypes in triploid Japanese eel (Anguilla japonica) induced by heat shock

  K Nomura; H Kagawa; H Tanaka; K Okuzawa; T Unuma; K Arai

  AQUACULTURE 247 1-4 20 - 20 2005年06月 [査読有り]
  
• Relationship between egg specific gravity and egg quality in the Japanese eel, Anguilla japonica

  Tatsuya Unuma; Shigenori Kondo; Hideki Tanaka; Hirohiko Kagawa; Kazuharu Nomura; Hiromi Ohta

  Aquaculture 246 1-4 493 - 500 2005年05月 

  Eggs from maturation-induced Japanese eels, Anguilla japonica, often sink in seawater immediately after artificial insemination and do not hatch. In the present study, the specific gravity of unfertilized eggs from individual females was measured in isotonic (about 310 mOsm/kg) and hypertonic (about 875 mOsm/kg) saline solutions and the relation of specific gravity to egg quality was examined. Egg specific gravity under isotonic conditions showed a significant negative correlation with egg fertility, hatchability and water content, suggesting that inadequate hydration of oocytes during final maturation, which leads to insufficient egg buoyancy, is one of the causes of poor egg quality. Some of the eggs that showed lower specific gravity than seawater under isotonic conditions exhibited higher specific gravity than seawater under hypertonic conditions, indicating that the buoyancy acquired by the eggs is sometimes lost after their transfer to seawater. Only eggs that retained low specific gravity under hypertonic as well as isotonic conditions exhibited high fertility and hatchability. Taken together with data from other studies, these results suggest that the poor quality of eggs that sink immediately after artificial insemination is attributable to at least two causes: the failure of oocytes to acquire sufficient buoyancy during maturation and the loss of buoyancy in seawater because of the inability of egg osmoregulation. © 2005 Elsevier B.V. All rights reserved.
• The first success of glass eel production in the world: basic biology on fish reproduction advances new applied technology in aquaculture

  Hirohiko Kagawa; Hideki Tanaka; Hiromi Ohta; Tatsuya Unuma; Kazuharu Nomura

  FISH PHYSIOLOGY AND BIOCHEMISTRY 31 2-3 193 - 199 2005年04月 [査読有り]
   

  The eel has long been esteemed as an important food fish in the world, especially in Japan, and has been used as an experimental fish for many fields of fish physiology. However, the decreases in eel resources have been a serious concern in recent years. The catches of glass eels as seedlings for aquaculture have shown a long-term decrease in both Europe and East Asia. To increase eel resources, the development of techniques for artificial induction of maturation and spawning and rearing their larvae have been eagerly desired. Recent progress of reproductive physiology of fish, especially mechanisms of oocyte maturation and ovulation in female and of spermatozoa maturation in male, facilitate to establish techniques for hormonal induction of maturation and spawning in sexually immature eels. With persistent effort to development of rearing techniques of larvae, we have first succeeded to produce glass eel. These applied techniques are may contribute to understand the basic reproductive physiology of the eel.
• Determination of the rates of fertilization, hatching and larval survival in the Japanese eel, Anguilla japonica, using tissue culture microplates

  T Unuma; S Kondo; H Tanaka; H Kagawa; K Nomura; H Ohta

  AQUACULTURE 241 1-4 345 - 356 2004年11月 

  A method was developed for assessing fertility, hatchability and larval survival in the Japanese eel, Anguilla japonica. Fertilized eggs were stocked in 24-, 48-, and 96-well plates at one egg to one well and maintained at 23degreesC without removing dead larvae, changing the water or feeding. Upon hatching, the larvae were often trapped on the surface of the water where they died (surface death). The remaining larvae then showed rather stable survival in the three types of plates beyond the yolk-sac stage, which was completed by day 8 after hatching (DAH). Polyethylene glycol 6000 (PEG 6000) added to the rearing water at 1 or 10 mug/ml markedly suppressed surface death without apparent effect on hatchability, the survival profile or abnormality. These results indicated that the survival rate can be determined easily by stocking the fertilized eggs individually in the wells of microplates with water containing PEG 6000 and by rearing the hatched larvae until the completion of yolk absorption, with little management. By this method, a series of parameters for evaluating the egg quality, rates of fertilization, hatching, survival and abnormality were determined in the artificially maturation-induced Japanese eel: unstable fertility and frequent abnormal development were revealed to be impediments to constant production of larvae at first feeding. (C) 2004 Elsevier B.V. All rights reserved.
• Development of endocrine system regulating exocrine pancreas and estimation of feeding and digestive ability in Japanese eel larvae

  T Kurokawa; N Iinuma; T Unuma; H Tanaka; H Kagawa; H Ohta; T Suzuki

  AQUACULTURE 234 1-4 513 - 525 2004年05月 

  To investigate the feeding and digestive physiology of early eel larvae, the development of cholecystokinin (CCK) and peptide YY (PYY) in the larval intestine, the feeding speed and pancreatic trypsin secretion in response to feeding were observed. CCK and PYY mRNA started to be expressed in the larval intestine at 8 days post-hatching (dph). This indicates that the pancreatic enzyme secretion is probably controlled by the CCK and PYY endocrine systems from the first feeding. Using fluorescein isothyiocyanate isomer (FITC)-labeled freeze-dried shark egg powder (Aquaran) as a diet, 10-dph eel larvae were estimated to feed at a rate of 0.04 mug Aquaran/min. The tryptic activity in the intestines of 11-dpb larvae increased approximately 4.2-fold at 1 h of feeding, whereas that in the pancreas remained constant. These results indicate that the digestive tract of these larvae recognized Aquaran as a nutrient, and that the exocrine pancreas secreted digestive enzymes into the intestine and began to synthesize digestive enzymes in response to feeding. (C) 2004 Elsevier B.V. All rights reserved.
• Induction of triploidy by heat shock in the Japanese eel Anguilla japonica

  K Nomura; J Nakajima; H Ohta; H Kagawa; H Tanaka; T Unuma; K Yamauchi; K Arai

  FISHERIES SCIENCE 70 2 247 - 255 2004年04月 

  Artificial reproduction and subsequent improved culture of the Japanese eel Anguilla japonica have not yet been achieved, but are expected in the near future. To allow the development of aquaculture activities, chromosome manipulation techniques are necessary for the genetic improvement of the eel. In the present paper suitable conditions were determined for heat shock treatment for the induction of triploidy. This was done using fertilized eggs obtained from gametes of cultured eels that were induced to mature by repeated injections of salmon pituitary extract, followed by an injection of 17alpha,20beta-dihydroxy-4-pregnen-3-one to induce ovulation in the female eels and by repeated injections of human chorionic gonadotropin in the male eels. Three variables (i.e. timing after fertilization, temperature, and duration of the shock) were varied to maximize the yield of triploid larvae by examining hatching and triploid rates of treated groups. Ploidy was determined by DNA content flow cytometry and/or chromosome counting. The triploid yield was the highest (70%), when a 37 degreesC heat shock was applied for 3 min, 10 min after fertilization. Under such conditions the rate of triploidy reached 70-100% and the rate of hatching was 5.2-24.6% when the control hatching rate was 28.5% on average.
• Otolith micro structural analysis of reared larvae of the Japanese eel Anguilla japonica

  A Shinoda; H Tanaka; H Kagawa; H Ohta; K Tsukamoto

  FISHERIES SCIENCE 70 2 339 - 341 2004年04月
• Effects of luteinizing hormone and follicle-stimulating hormone and insulin-like growth factor-I on aromatase activity and P450 aromatase gene expression in the ovarian follicles of red seabream, Pagrus major

  H Kagawa; K Gen; K Okuzawa; H Tanaka

  BIOLOGY OF REPRODUCTION 68 5 1562 - 1568 2003年05月 [査読有り]
   

  To clarify the mechanism of estradiol-17beta production in the ovarian follicle of red seabream, in vitro effects of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and insulin-like growth factor (IGF-1) on aromatase activity (conversion of testosterone to estradiol-17beta) and cytochrome P450 aromatase (P450arom) mRNA expression in ovarian fragments of red seabream were investigated. Of the growth factors used in the present study, only IGF-1 stimulated both aromatase activity and P450arom gene expression in the ovarian fragments of red seabream. LH from red seabream pituitary, but not FSH, stimulated both aromatase activity and P450arom gene expression. IGF-1 slightly enhanced the LH-induced aromatase activity and P450arom gene expression. These data and our previous results indicate that LH, but not FSH, stimulates estradiol-17beta production in the ovarian follicle of red seabream through stimulation of aromatase activity and P450arom gene expression and IGF-1 enhances the LH-stimulated P450arom gene expression.
• Role of prostaglandin in the control of ovulation in the Japanese eel Anguilla japonica

  H Kagawa; H Tanaka; T Unuma; H Ohta; K Gen; K Okuzawa

  FISHERIES SCIENCE 69 2 234 - 241 2003年04月 

  The in vitro effects of 17,20beta-dihydroxy-4-pregnen-3-one (DHP) and prostaglandins (PGE(1), PGE(2), PGF(1alpha), PGF(2alpha)) on ovulation in the Japanese eel Anguilla japonica were examined. Oocytes with follicle layers at the migratory nucleus stage (approximately 850-900 mum diameter) were removed using a polyethylene cannula from artificially matured fish. At concentrations of 10 and 100 ng/mL, DHP was found to induce both germinal vesicle breakdown and ovulation. The prostaglandins, except for PGE(1), effectively induced ovulation of previously matured oocytes by DHP treatment in vitro. Prostaglandin F-2alpha was the most effective. A significant increase in ovulation rate was observed even at a concentration of 0.01 mug/mL PGF(2alpha). Indomethacin blocked the in vitro ovulation induced by DHP and addition of PGF(2alpha) reversed indomethacin-blocked ovulation. Actinomycin D and cycloheximide blocked DHP-induced ovulation and PGF(2alpha) reversed the effects of both inhibitors. These results indicate that DHP induces ovulation through endogenous prostaglandin synthesis in the follicle layers of the Japanese eel.
• The first production of glass eel in captivity: fish reproductive physiology facilitates great progress in aquaculture

  H Tanaka; H Kagawa; H Ohta; T Unuma; K Nomura

  FISH PHYSIOLOGY AND BIOCHEMISTRY 28 1-4 493 - 497 2003年 

  Weekly injections of salmon pituitary extracts (SPE) were administered to female Japanese eel, Anguilla japonica at a dose of 20 mg/fish. This induced vitellogenesis and caused oocytes to reach the migratory nucleus stage. Later, a majority of the females that received an injection of SPE at a priming dose, followed 24 h later by 17,20beta-dihydroxy- 4-pregnen-3-one (DHP), ovulated 15 to 18 h after the final injection. In cultivated males, repeated injections of human chorionic gonadotropin (hCG) at a dose of 1 IU/g BW/week induced spermatogenesis and spermiation. Since potassium ions were revealed to be an essential constituent for the maintenance of motility in the eel spermatozoa, artificial seminal plasma containing KCl was designed as a diluent of milt, and enabled the preservation of milt for several weeks in refrigeration. As a result, artificial fertilization performed immediately after ovulation with pre-diluted and stocked milt consistently resulted in the production of high-quality gametes. Recently, a slurry-type diet made from shark egg yolk has been found to be a suitable feed for captive-bred eel larvae. Although preleptocephalus larvae can be reared with this diet beyond the depletion of their yolk and oil droplet stores, it remains inadequate because larvae reared under this way cannot be raised to the following stage. Therefore, the diet was improved by supplements of krill hydrolysate, soybean peptide, vitamins and minerals. Larvae fed on this new diet have grown to 50 to 60 mm in total length (TL), and have begun to metamorphose into glass eels approximately 250 days after hatching.
• Biochemical composition of eggs in relation to egg quality in the Japanese eel, Anguilla japonica

  H Furuita; H Ohta; T Unuma; H Tanaka; H Kagawa; N Suzuki; T Yamamoto

  FISH PHYSIOLOGY AND BIOCHEMISTRY 29 1 37 - 46 2003年 

  This paper presents the relationship between egg quality and egg biochemical composition of cultured and wild Japanese eel, Anguilla japonica. Eggs were obtained by artificial induction of maturation. Fertilization and hatching rates were used as characteristics of egg quality. Egg quality characteristics showed large variation; fertilization rate, 0 - 96; hatching rate, 0 - 84%. The biochemical composition also showed a large variation. There was no marked relationship between egg quality and fatty acid contents of eggs, except for n-6 highly unsaturated fatty acids (HUFA). Both the fertilization and hatching rates increased proportionally with increases of the alpha-tocopherol g(alpha-Toc) content in eggs. A more significant correlation was found between the amount of alpha-Toc relative to the amount of HUFA and egg quality. The results of this study show that the egg quality of Japanese eel is affected by the alpha-Toc level, and in particular, the ratio of alpha-Toc to HUFA in the eggs.
• Physiological roles of FSH and LH in red seabream, Pagrus major

  K Gen; S Yamaguchi; K Okuzawa; N Kumakura; H Tanaka; H Kagawa

  FISH PHYSIOLOGY AND BIOCHEMISTRY 28 1-4 77 - 80 2003年 [査読有り]
   

  The duality of gonadotropins (GTHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), has been confirmed in most teleost species, but very little is known about their biological functions. To elucidate the physiological roles of FSH and LH in fish reproduction, the expression profiles of GTH subunit genes during gonadal development were analyzed in both male and female red seabream. Furthermore, in vitro studies were carried out to examine the effects of GTHs on steroid hormone production and cytochrome P450 aromatase (P450arom) expression in red seabream gonads. In both sexes, LHbeta mRNA was maintained at high levels from the early gametogenesis until spawning season, and declined with gonadal regression. Interestingly, FSHbeta mRNA levels in males increased in parallel with testicular development, whereas those in female were remained low throughout oocyte development. From in vitro studies using purified red seabream FSH and LH, both GTHs had a similar potency in stimulating 11-ketotestosterone production by testicular slices, while the biological activity of FSH was much lower than that of LH in stimulating production of estradiol-17beta by vitellogenic follicles. Moreover, expression of P450arom mRNA was induced by LH, but not FSH, in ovarian follicles in vitro. FSH was also ineffective in inducing maturational competence and final oocyte maturation. These results suggest that, unlike salmonids, FSH may play an important role during gametogenesis in male, but not female, red seabream, whereas LH may be involved in regulation of both early and late gametogenesis in both sexes.
• Occurrence of spontaneous polyploids from the eggs obtained by artificial induction of maturation in the Japanese eel (Anguilla japonica)

  H Ohta; Y Higashimoto; S Koga; T Unuma; K Nomura; H Tanaka; H Kagawa; K Arai

  FISH PHYSIOLOGY AND BIOCHEMISTRY 28 1-4 517 - 518 2003年 [査読有り]
   

  The nuclear DNA contents of the Japanese eel larvae were measured to examine the genetic soundness of the eggs obtained by artificial induction of maturation and fertilization. Of the 12.4% abnormal polyploid larvae, 77.9% were triploid and the rest were haploid, tetraploid, pentaploid, or aneuploid.
• Expression of pancreatic enzyme genes during the early larval stage of Japanese eel Anguilla japonica

  Tadahide Kurokawa; Tohru Suzuki; Hiromi Ohta; Hirohiko Kagawa; Hideki Tanaka; Tatsuya Unuma

  Fisheries Science 68 4 736 - 744 2002年08月 

  To reveal the ontogeny of pancreatic exocrine function in the early larval stage of eel, cDNAs encoding major pancreatic enzymes, trypsinogen, amylase and lipase were identified from the Japanese eel Anguilla japonica and their expression pattern in larvae was analyzed. The cloned eel trypsinogen precursor consisted of 224 amino acids and showed 82.2% identity to trypsinogen-2 of winter flounder Pleuronectes americanus. The eel amylase precursor consisted of 512 amino acids and showed 77% identity to winter flounder amylase. Eel pancreatic lipase was composed of 470 amino acids and had 58.3% of identity to human pancreatic lipase. In the eel larvae, mRNA expression of trypsinogen and amylase was first detected at 6 days post-hatching (d.p.h.), and the expression level increased between 7 and 8 d.p.h. In contrast, mRNA expression of lipase was first detected at 8 d.p.h. Eel larvae start to feed actively at 8 d.p.h. Thus, it was indicated that eel pancreas starts to synthesize digestive enzymes at 6 d.p.h. and acquires full function by the onset of exogenous feeding at 8 d.p.h.
• Sexual dimorphism of gonadotropin I beta gene expression in red seabream, Pagrus major

  Koichiro Gen; Koichi Okuzawa; Hideki Tanaka; Hirohiko Kagawa

  FISHERIES SCIENCE 68 671 - 674 2002年 [査読有り]
   

  Gonadotropins, FSH and LH, play a central role in mammalian reproductive process. In teleost, as in mammals, two distinct gonadotropins, GTH-I and GTH-II, have been isolated and characterized in many teleost species. However, with the exception of salmonids, the physiological significance of GTH-I and GTH-Il in reproductive process is unclear at this lime. This article focuses on physiological roles of GTH-I and GTH-II in male and female red seabream. The expression profiles of GTH subunit genes in red seabream during sexual maturation revealed that the levels of I beta mRNA of male increased in association with gonadal development, whereas those of female were maintained at low levels. In contrast, II beta mRNA levels of both sexes were maintained at high levels from the beginning of gametogenesis to spawning season. Furthermore, in vitro studies demonstrated that GTH-II is more potent than GTH-I in stimulating estradiol-17 beta production and cytochrome P450 aromatase expression by vitellogenic follicles, while both GTH-I and GTH-II have similar potency in 11-ketotestosterone production in testicular slices. In addition, GTH-II, but not GTH-I, induced in vitro final oocyte maturation. These results suggest that GTH-II have important roles in reproduction of both male and female red seabream, while GTH-I shows sexual dimorphism in the expression of gonadotropin subunit genes and physiological function; GTH-I is functional molecule in male, but not in female red seabream.
• Recent progress of research on larvae production of Japanese eel, Anguilla japonica.

  KAGAWA H

  Suisanzoshoku 49 127 - 132 2001年10月 [査読有り]
  
• Production of leptocephali of Japanese eel (Anguilla japonica) in captivity

  H. Tanaka; H. Kagawa; H. Ohta

  Aquaculture 201 1-2 51 - 60 2001年09月 [査読有り]
   

  Despite intensive research on wild and captive eels, no resource has so far provided access to all life cycle stages of the Japanese eel Anguilla japonica. The transition from the preleptocephalus (newly hatched larva) to the leptocephalus stage (typical leaf-like eel larva) has, therefore, remained the missing link in the eel life cycle. We recently found that a slurry-type diet made from shark egg powder is suitable feed for captive-bred eel larvae. The larvae were successfully reared with this diet in aquaria for 100 days and raised to 22.8 mm in total length (TL). Age, TL, and body proportions of the reared specimens overlapped with those of wild leptocephali. We revealed for the first time the transition from the preleptocephalus to the leptocephalus stage of the eel. © 2001 Elsevier Science B.V. All rights reserved.
• Control by the environmental concentration of ions of the potential for motility in Japanese eel spermatozoa

  H Ohta; H Kagawa; H Tanaka; T Unuma

  AQUACULTURE 198 3-4 339 - 351 2001年07月 

  We examined the effects in vitro of the ionic composition of the incubation medium on the acquisition and loss of the potential for motility by the spermatozoa of the Japanese eel (Anguilla japonica). Milt were obtained from 10 males that had been artificially matured by repeated injections of hCG. The percentage of motile spermatozoa in the milt samples varied widely (mean, 53.4 +/- 11.8%; range, 7.4-91.5%) when samples were diluted with a hyperosmotic solution (450 mM NaCl buffered at pH 7.5). The percent motility increased significantly after a 60-min incubation in artificial seminal plasma (ASP), consisted of 149.3 mM NaCl, 15.2 mM KCl, 1.3 mM CaCl2, 1.6 mM MgCl2, and 20 mM NaHCO3, buffered with 20 mM TAPS-NaOH at pH 8.1, or in Ca2+- and Mg2+-free ASP (83.4 +/- 2.5% and 86.1 +/- 2.1%., respectively). A rapid decrease in motility was observed in Kf-free ASP (1.8 +/- 0.7%) and in HCO, free ASP (5.7 +/- 2.2%). The percent motility increased with increasing concentrations and decreased with decreasing concentrations of K+ ions (0-30 mM) and HCO3- ions(0-20 mM) in the ASP. The cycle of acquisition and loss of the potential for motility could be repeated several times by changing the concentrations of K+ or HCO, ions in the ASP. These results strongly suggest that variations in the quality of milt obtained from artificially matured males might be related to the ionic constituents of the seminal plasma. The percent motility of eel spermatozoa could be controlled by adjusting the concentrations of K+ and HCO3- ions in the isotonic incubation medium, irrespective of the initial potential for motility. (C) 2001 Elsevier Science B.V. All rights reserved.
• Unique expression of gonadotropin-I and -II subunit genes in male and female red seabream (Pagrus major) during sexual maturation

  K Gen; K Okuzawa; B Senthilkumaran; H Tanaka; S Moriyama; H Kagawa

  BIOLOGY OF REPRODUCTION 63 1 308 - 319 2000年07月 [査読有り]
   

  Two distinct gonadotropins (GTHs) have been demonstrated in a number of teleost fishes. Although the physiological roles of GTHs have been extensively studied in salmonids, little is known about their biological functions in nonsalmonid fishes. In this study, to elucidate the role of GTH-I and GTH-II in reproduction, we cloned the alpha-glycoprotein subunit (alpha GSU) and gonadotropin beta subunits (I beta and II beta) of red seabream using the 5'- and 3'-RACE methods and used these cDNA probes to reveal changes in mRNA levels of each subunit during sexual maturation of both male and female red seabream. The nucleotide sequences of alpha GSU, I beta, and II beta are 629, 531, and 557 base pairs long, encoding peptides of 117, 120, and 146 amino acids, respectively. The deduced amino acid sequence of each mature subunit showed high homology with those of other teleosts. Northern blot analysis showed that I beta mRNA levels of males increase in association with gonadal development, whereas those of females remain low throughout sexual maturation, indicating sexual dimorphism in the expression pattern of I beta. In contrast, II beta mRNA levels of both sexes are maintained at high levels from the beginning of gametogenesis to spawning season. These results are different than those of salmonids and suggest that GTH-I may have important roles in male, but not female, gametogenesis. GTH-II may be involved in regulation of early and late gametogenesis in both male and female red seabream.
• GTH II but not GTH I induces final maturation and the development of maturational competence of oocytes of red seabream in vitro

  H Kagawa; H Tanaka; K Okuzawa; M Kobayashi

  GENERAL AND COMPARATIVE ENDOCRINOLOGY 112 1 80 - 88 1998年10月 [査読有り]
   

  The effects of red seabream gonadotropins (PmGTH I and PmGTH II) on the induction in vitro of germinal vesicle breakdown (GVBD) and the development of maturational competence (responsiveness to maturation-inducing steroid) were examined in the oocytes of red seabream. PmGTH II was highly effective in inducing GVBD in both maturationally incompetent (45.6 +/- 3.2% GVBD at a concentration of 300 ng/ml) and competent oocytes (42.3 +/- 0.4% GVBD at a concentration of 300 ng/ml). 17,20 Chi-Dihydroxy-4-pregnen-3-one (DHP, 10 ng/ml) increased the frequency of GVBD induced by PmGTH II. PmGTH I (33, 100, 300, and 900 ng/ml) a as unable to induce GVBD at any tested concentration in the presence or absence of DHP. Actinomycin D (1 mu g/ml) and cycloheximide (1 mu g/ml) totally inhibited the PmGTH II-induced GVBD in the presence and in the absence of DHP! Both PmGTH I and PmGTH II stimulated in vitro production of 11-ketotestosterone in sliced testes of red seabream in a similar potency. These results indicate that PmGTH II, but not PmGTH I, induces the final maturation of oocytes, as well as the development of the maturational competence of oocytes, in red seabream. (C) 1998 Academic Press.
• Immunocytochemical identification of two distinct gonadotropic cells (GTH I and GTH II) in the pituitary of bluefin tuna, Thunnus thynnus

  H Kagawa; Kawazoe, I; H Tanaka; K Okuzawa

  GENERAL AND COMPARATIVE ENDOCRINOLOGY 110 1 11 - 18 1998年04月 [査読有り]
   

  Immunocytochemical identification of GTH I and GTH II cells in the pituitary of the bluefin tuna (Thunnus thynnus) was performed using antisera specific for the common alpha-subunit and the two distinct beta-subunits of tuna (Thunnus obesus) GTH I and GTH II. Cells of the dorsal part of the proximal pars distalis (PPD), in close association with somatotrophs, displayed immunoreactivity of GTHI beta. GTH II beta immunoreactivity was present in cells of the central part of the PPD and the external border of the pars intermedia. Anti-GTH alpha immunostained both GTH I beta- and GTH II beta-immunoreactive cells and also thyrotrophs. Both GTH I beta- and GTH II beta-immunoreactive cells were observed in immature bluefin tuna, although there were greater numbers of GTH II beta immunoreactive cells. These results suggest that GTH I and GTH II are synthesized in separate cells in the pituitary of the bluefin tuna. The localization and appearance of the two distinct gonadotropic cells of the tuna are compared with the salmonid arrangement. (C) 1998 Academic Press.
• Effects of Rearing Period in Seawater on Induced Maturation in Female Japanese Eel Anguilla japonica

  Hirohiko Kagawa; Norio Iinuma; Hideki Tanaka; Hiromi Ohta; Koichi Okuzawa

  Fisheries Science 64 1 77 - 82 1998年 [査読有り]
   

  The effects of rearing period in seawater on induced maturation by hormonal treatments were examined in the cultured female Japanese eels Anguilla japonica. The oocytes of female eel (30 month old) kept in seawater for 3 months completed vitellogeneisis by significantly smaller number of injection of salmon pituitary extracts than those of female kept in seawater for one week. Fertility and hatching rates were not significantly different between the oocytes of the two experimental groups. Similar results were obtained in the experiment which was performed using 6-month older females. These results indicate that long term rearing in seawater increased responsiveness to salmon pituitary extract in ovarian maturation. Histological observation revealed that oocytes of females kept in seawater for 3 months became large and attained at the primary yolk globule stage, whereas oocytes of the females kept in seawater for one week were at the oil drop stage. Electron microscopic observation showed that gonadotrophs became active in the pituitary of females kept in seawater for 3 months. These results are the first findings showing that vitellogenesis is triggered under artificial rearing condition without any hormone treatments in cultured immature eels. These morphological results indicate that long term rearing in seawater induces vitellogneisis in the females, resulting in the shortened period for compeletion of vitellogeneisis by the injection of salmon pituitary extract.
• Artificial induction of maturation and fertilization in the Japanese eel, Anguilla japonica

  H Ohta; H Kagawa; H Tanaka; K Okuzawa; N Iinuma; K Hirose

  FISH PHYSIOLOGY AND BIOCHEMISTRY 17 1-6 163 - 169 1997年12月 [査読有り]
   

  Repeated injections of salmon pituitary extract (20 mg per fish per week) induced vitellogenesis in feminized, cultivated Japanese eels (Anguilla japonica). Oocytes were attained at the migratory nucleus stage after 11 or 12 injections. Addition of 17,20 beta-dihydroxy-4-pregnen-3-one (DHP) into the incubation medium induced germinal vesicle breakdown (GVBD) in the oocytes at the migratory nucleus stage. An injection of DHP (2 mu g g(-1) BW), given 24h after an injection of salmon pituitary extract (20 mg fish(-1)), succeeded in inducing maturation and ovulation in females which contained occytes at the migratory nucleus stage. Most fish ovulated 15-18h following the DHP injection. Eggs that were ovulated within 15h after the DHP injection showed high fertility and hatchability, but eggs ovulated 18 or 21h after the DHP injection, showed considerably lower fertility and hatchability. A delay between ovulation and stripping of the eggs rapidly decreased both the fertility and hatchability within 6-9h after ovulation, indicating that artificial fertilization must be carried out immediately after ovulation. Repeated injections of human chorionic gonadotropin (hCG) at a concentration of 1 IU g(-1) BW week(-1) induced spermatogenesis, spermiation, and the acquisition of potential for sperm motility in cultivated males. Most males spermiated after the fifth or sixth injection of hCG, and the milt weight gradually increased and remained constant (1-2 g) from the 11th to 31th injection. Sperm motility peaked 24h after each weekly injection, and decreased from the 3(rd) day after the injection. Potassium ions are an essential constituent for the maintenance of motility in the eel spermatozoa. Artificial seminal plasma containing 15.2 mM KCl is applicable as a milt diluent. Using these techniques developed for female and male eels, we have succeeded in obtaining many fertilized eggs from cultivated eels.
• Relationship between serum levels of human chorionic gonadotropin (hCG) and 11-ketotestosterone after a single injection of hCG and induced maturity in the male Japanese eel, Anguilla japonica

  Hiromi Ohta; Hideki Tanaka

  Aquaculture 153 1-2 123 - 134 1997年06月 [査読有り]
   

  A single injection of human chorionic gonadotropin (hCG) administered to sexually immature male Japanese eels (Anguilla japonica) at a dose of 8 IU g-1 body weight induced spermatogenesis. Thirty-five days after the injection, all 18 treated fish had spermatozoa in their testes and three exhibited the spermiation response. However, the degree of maturity of treated fish varied widely. Gonadosomatic indices (GSIs), examined 35 days after the injection, ranged from 0.27 to 8.20%, while those of control fish ranged from 0.13 to 0.20%. Mean serum levels of hCG peaked 1 clay after the injection (25 900 ± 800 mIU ml-1), and then the levels decreased. Correlation coefficients between the individual levels of hCG measured 1, 3, 7, 14, 21 and 28 days after the injection and GSI increased with time, becoming significant 14 days after the injection. The mean level of hCG in six treated fish, with GSIs of more than 2.0%, was 165 ± 54 mIU ml-1 on day 28. The mean level was considerably higher than the level (50 mIU ml-1) previously used in vitro for this species. In contrast, the mean level of hCG of seven males with a GSI of less than 0.5% was 9.87 ± 7.60 mIU ml-1 on day 21 and 1.09 ± 0.21 mIU ml-1 on day 28. Mean serum levels of 11-ketotestosterone (II-KT) peaked 3 days after the injection (20.4 ± 1.7 ng ml-1), and showed a gradual decrease, reaching 2.7 ± 0.8 ng ml-1 on day 28. The correlation coefficient between levels of 11-ketotestosterone and the GSI also became significant 21 days after the injection. Furthermore, the correlation coefficient between levels of hCG and 11-KT became significant 14 days after the injection. These results indicate that the effectiveness of a single injection of hCG in inducing spermatogenesis is affected to a considerable extent by individual differences in the clearance rates of hCG between fish.
• Induced ovulation by injection of 17, 20β dihydroxy-4-pregnen-3-one the artificially matured Japanese eel, with special reference to ovulation time.

  Hirohiko Kagawa; Hideki Tanaka; Hiromi Ohta; Koichi Okuzawa; Norio Iinuma

  Fisheries Sci. 63 3 365 - 367 1997年 [査読有り]
   

  The effects of injection of 17,20β-dihydroxy-4-pregnen-3-one (DHP) on induced ovulation in the artificially matured Japanese eel Anguilla japonica were examined, with special reference to the effect of injection time on the time of ovulation. Ovulation occurred 18 h and 21 h after injection of DHP at 9:00, in 10 of 15 females and in the remaining 5 females, respectively. Injection of DHP at 18:00 induced ovulation 15, 18, and 21 h after injection in 4, 12, and 2 of 18 females, respectively. Fertility and hatching rates were not significantly different between females which ovulated 18 h after injection at 9:00 or 18:00. In the second experiment, eggs from females which ovulated 15 h after DHP injection showed significantly higher fertility (about 63%) and hatching rates (about 54%) than eggs from females which ovulated 18 h after the injection. These results indicate that the time of ovulation depends on the time elapsed after the DHP injection in the eel.
• Artificial Fertilization Using Testicular Spermatozoa in the Japanese Eel Anguilla japonica

  Hiromi Ohta; Hideki Tanaka; Hirohiko Kagawa; Koichi Okuzawa; Norio Iinuma

  Fisheries Science 63 3 393 - 396 1997年 [査読有り]
   

  The motility and fertility of the Japanese eel testicular spermatozoa, which had acquired motility during an incubation with K30 solution (consisting of 30 mM KCl, 134.5 mM NaCl, 1.3 mM CaCl2, 1.6 mM MgCl2, 20 mM NaHCO3, and buffered with 20 mM TAPS-NaOH at pH 8.1), were compared with those of the milt spermatozoa obtained from the genital pore of a Japanese eel. The motility percentages of milt spermatozoa and testicular milt spermatozoa, were 84.7 ± 4.1% and 2.6 ± 1.9%, respectively. The percent motility of incubated testicular milt spermatozoa was 63.3 ± 2.2%. The fertility and hatchability of the milt and incubated testicular milt were significantly higher than those of testicular milt. There were no significant differences found between the fertility and hatchability of the milt and those of the incubated testicular milt. To examine the toxicity of the high potassium concentration in the K30 solution on egg fertility, we compared the fertility and hatchability of milt spermatozoa diluted with K30 solution or K15 solution. No significant differences in the fertility or hatchability were found between the K30 and the K15 solutions. These results indicate that the testicular spermatozoa which acquired motility during their incubation in K30 solution are just as fertile as the motile milt spermatozoa, and that K30 solution is suitable as a milt diluent in the artificial fertilization of the eel.
• Milt Production in the Japanese Eel Anguilla japonica Induced by Repeated Injections of Human Chorionic Gonadotropin

  Hiromi Ohta; Hirohiko Kagawa; Hideki Tanaka; Koichi Okuzawa; Keiji Hirose

  Fisheries Science 62 1 44 - 49 1996年 [査読有り]
   

  Sexually immature male eels (253 g average body weight), reared in sea water at 20°C, were injected weekly (14 times in total) with human chorionic gonadotropin (HCG) at a concentration of 250 or 750 IU/fish/week. Changes of the milt weight and milt quality were examined two days after each injection. Some of the treated males of both the 250 IU and 750 IU groups spermiated after the 5th injection, and most males spermiated after the 6th injection. In the 250 IU group, the milt weight gradually increased with increase in the repetitions of injection. It became constant (1-2 g) during the period of the 11th-13th injection, and reached 4.0 g after the 14th injection. Acquisition of potential for sperm motility was attained during the period of the 7th-9th injections and the percent motility of spermatozoa at 15 sec after dilution with 450 mM NaCl remained at approximately 70% until after the 14th injection. Milt pH (8.1-8.2) during the period of the 7th-9th injection was significantly higher than the 10th-11th injection period. Serum 17,20β-dihydroxy-4-pregnen-3-one levels in the males of both groups remained low (0.1-0.2 ng/ml) throughout the experiment, although they were significantly higher than the saline control levels (0.05-0.08 ng/ml). In the 750 IU group, there was a marked difference in milt weight between individual males. The mean total milt weight throughout the experiment per fish of the 250 IU group was 9.4 g, and that of the 750 IU group was 6.1 g. The results indicate that repeated weekly injections of HCG at 250 IU/fish (about 1 IU/gBW) over 10 weeks is efficient for the artificial maturation of immature male eels.
• Absorption of Protein Molecules by the Rectal Cells in Eel Larvae Anguilla japonica

  Tadahide Kurokawa; Hideki Tanaka; Hirohiko Kagawa; Hiromi Ohta

  Fisheries Science 62 5 832 - 833 1996年 [査読有り]
  
• Changes in fertilization and hatching rates with time after ovulation induced by 17、20β-dihydroxy-4-pregnen-3-one in the Japanese eel, Anguilla japonica.

  H Ohta; H Kagawa; H Tanaka; K Okuzawa; K Hirose

  Aquaculture 139 3-4 291 - 301 1996年01月 [査読有り]
   

  This study examined the time to ovulation in artificially matured Japanese eel following an injection of 17, 20 beta-dihydroxy-4-pregnen-3-one (DHP), and changes in fertilization and hatching rates at various times after ovulation. Thirteen females, showing body weight indices (body weight/initial body weight X 100) of 119 +/- 2.3% with oocytes at the migratory nucleus stage after 9-12 weekly injections of salmon pituitary extract (20 mg pituitary powder /fish/week), received an injection of salmon pituitary extract (20 mg/fish) followed 24 h later by a DHP injection (2 mu g/g BW) for induction of ovulation. Eleven of 13 females ovulated within 23 h of the final injection; two, seven, and two females ovulated at 14-17 h, 17-20 h and 20-23 h after the final injection, respectively, The remaining two did not ovulate within 26 h of the injection, Eggs from three out of the 11 ovulated females showed relatively high percent fertility (89.6-39.5%) and hatching rates (47.6-15.3%) when they were fertilized after the first detection of ovulation. Both percent fertilization and hatching rates of eggs retained in the body cavity decreased rapidly within 6-9 h after ovulation, These results indicate that ovulation induced by DHP treatment occurs after a short but well-defined period of time, and that artificial fertilization must be carried out immediately after ovulation in order to obtain good quality eggs.
• Development of the exocrine pancreas in the larvae of Japanese eel (Anguilla japonica).

  Kurokawa, T; H. Kagawa; H. Ohta; H. Tanaka; K. Okuzawa; K. Hirose

  Canad. J. Fish. Aquat. Sci. 52 5 1030 - 1036 1995年07月 [査読有り]
   

  As part of a study on the early life of Japanese eel, the development of the digestive organs was observed during the 13 d after hatching. The digestive tract was formed only at the pharynx at hatching; the posterior part of the duct differentiated during 1 d posthatch (DPH). Pancreas and liver started to develop at 3 DPH. Immunohistochemistry using an antibody to eel trypsinogen showed weak signals first appearing in the pancreas at 6 DPH, suggesting that the eel pancreas starts to synthesize digestive enzymes at 6 DPH. The immunohistochemical signals became strong at 7 DPH, at which time the mouth opening orientation moved from ventral to anterior, the intestine differentiated into small intestine and rectum and the yolk was absorbed. Rotifers were first observed in the digestive tract of 13-d-old larvae. We inferred from the developmental process of the digestive organs that the larvae can start feeding at 7 DPH, which is earlier than observations of first feeding.
• The First Report of Eel Larvae Ingesting Rotifers

  Hideki Tanaka; Hirohiko Kagawa; Hiromi Ohta; Koichi Okuzawa; Keiji Hirose

  Fisheries Science 61 1 171 - 172 1995年 [査読有り]
  
• In vitro effects of 17α,20β-dihydroxy-4-pregnen-3-one on final maturation of oocytes at various developmental stages in the Japanese eel, Anguilla japonica.

  Hirohiko Kagawa; Hideki Tanaka; Hiromi Ohta; Koichi Okuzawa; Keiji Hirose

  Fisheries Sci. 61 6 1012 - 1015 1995年 [査読有り]
   

  In vitro effects of 17α-hydroxyprogesterone and 17α,20βS-dihydroxy-4-pregnen-3-one (DHP) on germinal vesicle breakdown (GVBD) of oocytes at various developmental stages were examined in artificially matured Japanese eel. Neither 17α-hydroxyprogesterone nor DHP induced GVBD in oocytes at a tertiary yolk stage ranging from 600-700 μm in diameter. Oocytes at a migratory nucleus stage ranging from 700 to 800 μm in diameter underwent GVBD in response to 17α-hydroxyprogesterone and DHP at concentrations of 10 and 100 ng/ml. Oocytes over 800 αm in diameter became more sensitive to the steroids. These results suggest that oocytes acquired the ability to respond to the maturation-inducing steroid at the migratory nucleus stage. Also, oocyte diameter and its microscopic features can be utilized as a reliable indicator of the induced maturation and ovulation by the injection of the steroids. © 1995, The Japanese Society of Fisheries Science. All rights reserved.
• MOLECULAR-CLONING OF A CDNA-ENCODING THE PREPRO-SALMON GONADOTROPIN-RELEASING-HORMONE OF THE RED SEABREAM

  K OKUZAWA; K ARAKI; H TANAKA; H KAGAWA; K HIROSE

  GENERAL AND COMPARATIVE ENDOCRINOLOGY 96 2 234 - 242 1994年11月 [査読有り]
   

  Complementary DNA fragments encoding the prepro-salmon gonadotropin-releasing hormone ([Trp(7), Leu(8)]GnRH, sGnRH) of the red seabream Pagrus major were amplified from mRNA of the olfactory bulbs using a reverse transcriptase-polymerase chain reaction (RT-PCR), and the full-length cDNA was cloned from a cDNA library using the PCR-amplified cDNA as a probe. The cDNA consisted of 442 bp, including an open reading frame of 270 bp which encoded the prepro-sGnRH (90 amino acid residues). The prepro-sGnRH had the same architecture as that reported in other species. It was composed of a signal peptide, sGnRH and a GnRH-associated peptide (GAP), which was connected to sGnRH by a Gly-Lys-Arg sequence. The prepro-sGnRH of the red seabream had 90% amino acid identity to the prepro-sGnRH from an African cichlid Haplochromis burtoni which belongs to the same suborder as the red seabream; however, identity was lower to the prepro-sGnRH from Atlantic salmon Salmo salar (74%) and masu salmon Oncorhynchus masou (70%). The GnRH peptide itself and the Gly-Lys-Arg sequence in the prepro-GnRH are highly conserved among vertebrates. The red seabream GAP also shows significant amino acid identity to the GAPs of the African cichlid (89%), Atlantic salmon (74%), and masu salmon (67%), but exhibits no significant identity to chicken or mammalian GAP. (C) 1994 Academic Press, Inc.
• DEVELOPMENT OF MATURATIONAL COMPETENCE OF OOCYTES OF RED SEABREAM, PAGRUS-MAJOR, AFTER HUMAN CHORIONIC-GONADOTROPIN TREATMENT IN-VITRO REQUIRES RNA AND PROTEIN-SYNTHESIS

  H KAGAWA; H TANAKA; K OKUZAWA; K HIROSE

  GENERAL AND COMPARATIVE ENDOCRINOLOGY 94 2 199 - 206 1994年05月 [査読有り]
   

  The effects of human chorionic gonadotropin (HCG) and 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (DHP) on in vitro germinal vesicle breakdown (GVBD) in oocytes obtained at different times of day from a daily spawning marine teleost, the red seabream Pagrus major, were investigated. Oocytes isolated at 0800 hr underwent GVBD in response to HCG (10 IU/ml) but not to DHP (10 ng/ml). GVBD could be induced in oocytes isolated at 1600 hr by either HCG or DHP. Oocytes underwent GVBD in response to DHP after DHP-insensitive oocytes were incubated with HCG for 30, 60, or 120 min. The effects of actinomycin D (a transcriptional inhibitor) and cycloheximide (a translational inhibitor) on HCG- and DHP-induced GVBD were also investigated. Actinomycin D (1 mu g/ml) totally inhibited HCG-induction of GVBD in oocytes isolated at 0600 and 0800 hr. Actinomycin D also significantly inhibited GVBD induced by HCG in combination with DHP in oocytes taken at 0600 and 0800 hr. Cycloheximide (1 mu g/ml) completely inhibited the induction of GVBD by HCG or DHP, alone or in combination, in oocytes obtained at 0600, 1000, and 1400 hr. These results indicate that gonadotropin induces maturational competence (responsiveness to maturation-inducing steroid) in oocytes of red seabream. These results also suggest that gonadotropin-induced synthesis of new protein through a mechanism dependent on RNA is essential for the development of maturational competence in oocytes of red seabream. (C) 1994 Academic Press, Inc.
• CHROMATOGRAPHIC AND IMMUNOLOGICAL IDENTIFICATION OF GONADOTROPIN-RELEASING-HORMONE IN 5 MARINE TELEOSTS

  K OKUZAWA; M AMANO; K AIDA; Y HASEGAWA; H TANAKA; H KAGAWA

  FISH PHYSIOLOGY AND BIOCHEMISTRY 12 4 337 - 345 1993年12月 [査読有り]
   

  Brain extracts from bluefin tuna, Thunnus thynnus, red seabream, Pagrus major, black seabream, Acanthopagrus schlegeli, red spotted grouper, Epinephelus akaara and Japanese flounder, Paralichthys olivaceus, were analyzed by high performance liquid chromatography (HPLC) and specific radioimmunoassays. Immunoreactive material co-eluting from HPLC with salmon gonadotropin-releasing hormone (GnRH) and chicken GnRH-II, respectively, was found in all five species. In addition, a GnRH immunoreactive fraction showing the same HPLC retention time as lamprey GnRH-I was detected in the brain extracts of all species examined when using an unspecific radioimmunoassay which detects several GnRH forms, including lamprey GnRH-I. In the Japanese flounder brain extract, a fourth GnRH immunoreactive fraction was detected with the unspecific radioimmunoassay which did not co-elute with any of the six synthetic GnRH standards used in the present study.
• DEVELOPMENT OF LHRH-A COPOLYMER PELLET POLYMERIZED BY ULTRAVIOLET AND ITS APPLICATION FOR MATURATION IN RED-SEA BREAM PAGRUS-MAJOR DURING THE NON-SPAWNING SEASON

  M MATSUYAMA; M HAMADA; T ASHITANI; M KASHIWAGI; T IWAI; K OKUZAWA; H TANAKA; H KAGAWA

  NIPPON SUISAN GAKKAISHI 59 8 1361 - 1369 1993年08月 [査読有り]
   

  A method is described for preparing a nonbiodegradable copolymer pellet containing luteinizing hormone-releasing hormone analogue (LHRH-a), des Gly(10)-[D-Ala(6)] LHRH ethylamide, polymerized by ultraviolet rays to produce sustained hormone release. The pellet was applied to induce gonadal development and maturation in red sea bream Pagrus major during the non-spawning season, from November to December. Single implantation of a copolymer pellet containing 100 mu g LHRH-a induced gonadal development and spawning in completely immature fish 18 days after implantation, about six months prior to the nutural spawning season. Fish implanted with a 50 mu g LHRH-a copolymer pellet or a control pellet were not induced to spawn. The histopathological findings of muscular tissues surrounding the implant showed that no inflammatory response to a foreign body appeared even one month after implantation. Results from the present study indicate that the LHRH-a copolymer pellets prepared by us have several features: (1) the pellets can be prepared easily and mass-produced at one time, (2) the pellets are useful for long-term hormone therapy in inducing sexual maturation in fish requiring a series of hormone treatments, and (3) the copolymer has good biocompatibility. However, the fertility rates of eggs produced were low. Further investigation is necessary to devise an effective method for obtaining more viable eggs by the use of copolymer pellets.
• PURIFICATION OF GONADOTROPINS (PMGTH-I AND PMGTH-II) FROM RED SEABREAM (PAGRUS-MAJOR) AND DEVELOPMENT OF A HOMOLOGOUS RADIOIMMUNOASSAY FOR PMGTH-II

  H TANAKA; H KAGAWA; K OKUZAWA; K HIROSE

  FISH PHYSIOLOGY AND BIOCHEMISTRY 10 5 409 - 418 1993年03月 [査読有り]
   

  Two gonadotropic glycoproteins (PmGTH I and II) were purified by ion-exchange chromatography, gel filtration and preparative SDS-PAGE, from pituitaries of red seabream, a marine teleost which has an asynchronous-type ovary and spawns almost daily during the spawning season. The glycoproteins were composed of distinct subunits and the molecular weights were estimated to be 32 and 38 kDa for PmGTH I and PmGTH II, respectively. Both PmGTH I and II were active in two homologous bioassays: in vitro oocyte maturation and/or in vitro estradiol-17beta production assays. These two GTHs were distinct in electrostatic properties, molecular weight, stability and yields from pituitaries during the spawning season. These properties suggest that PmGTH I and II correspond to salmon GTH I and II, respectively. A homologous radioimmunoassay with which to measure PmGTH II was developed using a rabbit antiserum against the beta subunit of PmGTH II and intact PmGTH II as standards and radioactive competitors. Competition curves for red seabream plasma and pituitary extract were parallel to the standard curve, while PmGTH I had low cross-reactivity (3.1%) with the antibody. This specific RIA system showed an in vivo LHRHa induced GTH surge in the plasma of female red seabream.
• 2 GONADOTROPIC GLYCOPROTEINS IN THE RED SEABEAM (PAGRUS-MAJOR)

  H TANAKA; H KAGAWA; K OKUZAWA; K HIROSE

  PROCEEDINGS OF THE FOURTH INTERNATIONAL SYMPOSIUM ON THE REPRODUCTIVE PHYSIOLOGY OF FISH 13 - 15 1991年 [査読有り]
  

書籍

• ウナギの科学

  田中 秀樹 (担当:分担執筆範囲:5.1 養鰻業の歴史と現状、5.4 種苗生産の歴史と現状)朝倉書店 2019年06月
• トコトンやさしい養殖の本

  田中 秀樹 (担当:分担執筆範囲:2 伸び続ける水産物需要を支える養殖、5 養殖水産資源の種類、37 ウナギの養殖)日刊工業新聞社 2019年02月
• 魚の形は飼育環境で変わる-形態異常はなぜ起こるのか？

  田中 秀樹 (担当:分担執筆範囲:Ⅰ．魚類人工種苗における形態異常とは何か？ 6章 ニホンウナギの種苗生産過程で発現する様々な形態異常)恒星社厚生閣 2017年06月
• ウナギの博物誌

  田中 秀樹 (担当:分担執筆範囲:第２部 食資源としてのウナギを考える．第6章 ウナギ完全養殖への挑戦)化学同人 2012年10月
• うなぎ 謎の生物

  田中 秀樹 (担当:分担執筆範囲:第４章 ウナギを育てる)築地書館 2012年07月
• 水産の２１世紀 海から拓く食糧自給

  田中 秀樹 (担当:分担執筆範囲:第２章 食糧問題の解決に貢献する増養殖漁業．第３節 人工種苗生産が天然ウナギの絶滅を救う)京都大学学術出版会 2010年08月
• Eel Biology

  田中 秀樹 (担当:分担執筆範囲:Part 7 Larval Rearing and Physiology. 29 Techniques for Larval Rearing)Springer-Verlag 2003年07月
• 水産学シリーズ107 ウナギの初期生活史と種苗生産の展望

  田中 秀樹 (担当:分担執筆範囲:Ⅱ．人工種苗生産の展望 10.孵化仔魚の飼育)恒星社厚生閣 1996年04月
• 水産学シリーズ85 海産魚の成熟・産卵リズム

  田中 秀樹 (担当:分担執筆範囲:Ⅱ．成熟・産卵とホルモン 3.生殖腺刺激ホルモン)恒星社厚生閣 1991年10月

MISC

• ブリ飼料の総抗酸化力が血合筋の褐変に及ぼす影響

  木原広貴; 山田伸一; 高桑史明; AMAL Biswas; 向井良夫; 田中秀樹 日本水産学会大会講演要旨集 2019 2019年
• 光制御が魚類の代謝,成長および生殖に及ぼす影響

  ビッシャシュ アマル; 滝井健二; 田中秀樹; 高桑史明; 竹内俊郎 日本水産学会大会講演要旨集 2019 2019年
• 魚粉の過加熱がシマアジ稚魚の成長およびin vitro消化性におよぼす影響

  高桑史明; 林翔太; 山田伸一; BISWAS Amal; 田中秀樹 日本水産学会大会講演要旨集 2019 2019年
• Isolation and characterization of bacteria causing mortality in early stage larvae of captive-bred Japanese eels (Anguilla japonica Temminck & Schlegel)

  Gentoku Nakase; Masaharu Tokuda; Kazuharu Nomura; Hideki Tanaka AQUACULTURE RESEARCH 46 (11) 2637 -2643 2015年11月 [査読有り]
  
• 養殖技術 ウナギの完全養殖

  太田 博巳; 田中 秀樹 科学と工業 86 (4) 109 -114 2012年04月
• Teratogenic effects of the chemicals used for assessing egg quality of Japanese eel with tissue culture microplates

  T. Unuma; T. Kurokawa; M. Tokuda; K. Nomura; H. Tanaka Aquaculture Sci. 59 (2) 307 -313 2011年 [査読有り]
  
• Spontaneous polyploids and mosaics in the progeny from artificially induced gametes of the Japanese eel, Anguilla japonica

  K. Nomura; Y. Takeda; K. Morishima; H. Tanaka; T. Unuma; K. Arai; H. Ohta AQUACULTURE 272 S295 -S296 2007年
• 精巣様の形態を呈する卵巣を有したウナギ

  松原 創; 田中 秀樹; 小林 亨; 吉川 昌之; 鈴木 淳志; 伊藤 雅夫 日本繁殖生物学会 講演要旨集 100 (0) 20052 -20052 2007年
• Effects of high levels of n-3 HUFA in broodstock diet on egg quality and egg fatty acid composition of Japanese flounder, Paralichthys olivaceus

  H Furuita; H Tanaka; T Yamamoto; N Suzuki; T Takeuchi AQUACULTURE 210 (1-4) 323 -333 2002年07月
• 2. ウナギの種苗生産技術開発研究の現状と展望(日本水産学会水産増殖懇話会)

  香川 浩彦; 田中 秀樹; 太田 博巳; Hirohiko Kagawa; Hideki Tanaka; Hiromi Ohta; 養殖研究所; 養殖研究所; 養殖研究所; National Research Institute of Aquaculture; National Research Institute of Aquaculture; National Research Institute of Aquaculture 日本水産学会誌 = Bulletin of the Japanese Society of Scientific Fisheries 66 (5) 930 -930 2000年09月
• ウナギの人工催熟技術と仔魚の飼育技術の開発に関する研究

  田中 秀樹; 太田 博巳; 香川 浩彦; 河村 章人; Hideki Tanaka; Hiromi Ohta; Hirohiko Kagawa 日本水産学会誌 = Bulletin of the Japanese Society of Scientific Fisheries 66 (3) 370 -370 2000年05月
• マダイの産卵期における血中17α, 20β-dihydroxy-4pregnen-3-one の日周変化

  香川 浩彦; 田中 秀樹; 奥澤 公一; 松山 倫也; 広瀬 慶二 日本水産学会誌 57 (4) 769 -769 1991年04月

産業財産権

• 特許第6952978号:ウナギ仔魚用飼料  

  古板 博文, 神保 忠雄, 樋口 理人, 田中 秀樹, 野村 和晴, 須藤 竜介, 松成 宏之  国立研究開発法人水産研究・教育機構  202103018223559732
• 特許第6209804号:ウナギ仔魚の飼育方法及び飼育装置並びに飼育用の容器  

  野村 和晴, 田中 秀樹, 古板 博文  国立研究開発法人水産研究・教育機構  201703001294655381
• 特開2015-082974:ウナギ目葉形仔魚の成長促進剤  2015年04月30日

  川上 優, 田中 秀樹, 野村 和晴  独立行政法人水産総合研究センター  201503026233705871
• 特許第5062594号:ウナギ仔魚などの浮遊生物用飼育水槽及び浮遊生物の給餌方法  

  増田 賢嗣, 田中 秀樹, 野村 和晴, 照屋 和久  独立行政法人水産総合研究センター  201303087964467567
• 特許第4530248号:ウナギ仔魚用飼料  

  田中 秀樹, 野村 和晴, 塩谷 格, 中森 俊宏, 古田 均  独立行政法人水産総合研究センター, 日本水産株式会社, 不二製油株式会社  201103073387335650
• 特許第2909536号:ウナギ孵化仔魚の飼育方法  

  田中 秀樹, 香川 浩彦, 太田 博巳  農林水産省水産庁養殖研究所長  201103090672480127

受賞

• 2012年04月 日本農学会 日本農学賞
   

  受賞者: 田中 秀樹
• 2011年03月 日本水産学会 水産学会賞
   

  受賞者: 田中 秀樹
• 2004年04月 日経BP社 日経BP技術賞 医療・バイオ部門賞
   

  受賞者: 田中 秀樹

共同研究・競争的資金等の研究課題

• 生殖腺刺激ホルモンによるマダイの初回成熟機構の解明

  日本学術振興会：科学研究費助成事業 基盤研究(C)

  研究期間 : 2011年 -2013年 

  代表者 : 奥澤 公一; 玄 浩一郎; 風藤 行紀; 田中 秀樹

   

  魚類の性成熟が開始する過程で中心的な役割を担う２種類の生殖腺刺激ホルモン（GTH）のうち、これまでは限られた種類の魚でしか確立していなかった濾胞刺激ホルモン（FSH）の濃度測定法をマダイについて新たに開発し、マダイFSHの分泌動態や分泌制御を調べ、マダイでは生殖腺刺激ホルモン放出ホルモンはFSH分泌を促進しないことを明らかにした。また、マダイのFSHともう一つのGTHである黄体形成ホルモン（LH）を恒常的に発現する細胞株を樹立し、数十ミリグラムレベルの組換えホルモンを作製することに成功した。今後はこのホルモンを用いたFSHおよびLH作用の詳細の解明と成熟促進技術の開発が期待される。
• ウナギ仔魚用人工配合飼料の改良と新規飼料の開発

  日本学術振興会：科学研究費助成事業 特別研究員奨励費

  研究期間 : 2009年 -2009年 

  代表者 : 田中 秀樹; KIM S.-K.

担当経験のある科目

水産増殖技術特論近畿大学大学院
魚類繁殖生理学近畿大学

その他のリンク

researchmap

https://researchmap.jp/180411