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Changes in Sex Steroids and Ovarian Steroidogenic Enzyme mRNA Levels in Artificially Maturing Japanese Eel (Anguilla japonica) and Naturally Maturing New Zealand Longfin Eel (Anguilla dieffenbachii) during Vitellogenesis

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Noto Center for Fisheries Science and Technology, Kanazawa University, 11-4-1 Ossaka, Noto-cho, Ishikawa 927-0552, Japan
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Department of Zoology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
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Research Center for Aquatic Breeding, Fisheries Research Agency, National Institute of Aquaculture, Tsuiura, Kamiura, Saiki, Oita 879-2602, Japan
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Division of Marine Biosciences, Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato cho, Hakodate, Hokkaido 041-8611, Japan
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Faculty Agriculture/Sanriku Fisheries Research Center, Department of Food Production & Environmental Management, Iwate University, 3-75-1 Heita, Kamaishi, Iwate 026-0001, Japan
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School of Aquatic and Fishery Sciences, University of Washington, Seattle 98195, WA, USA
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Center for Reproductive Biology, Washington State University, Pullman 99164, WA, USA
*
Author to whom correspondence should be addressed.
Fishes 2019, 4(4), 52; https://doi.org/10.3390/fishes4040052
Received: 18 September 2019 / Revised: 11 October 2019 / Accepted: 12 October 2019 / Published: 17 October 2019
Repeated hormone injections are routinely used to induce advanced stages of oogenesis in freshwater eels, but this approach may result in aberrant germ cell development. To investigate the underlying causes, levels of sex steroids (testosterone, T; estradiol-17β, E2) and ovarian steroidogenic enzyme mRNAs were compared between artificially maturing Japanese eels and wild-caught, spontaneously maturing New Zealand longfin eels. The latter were employed as reference, as wild Japanese eels in advanced stages of oogenesis are near-impossible to catch. Serum T levels in artificially maturing Japanese eel changed with stage in a pattern that was comparable to that in longfin eels. Likewise, ovarian mRNA levels of most steroidogenic enzyme genes were not qualitatively dissimilar between both eel species when taking developmental stage into account. However, aromatase (cyp19a) mRNA levels, together with serum E2 levels, rapidly increased in artificially maturing Japanese eels in mid-late stages of oogenesis (gonadosomatic index, GSI = 13.8%), whereas no such increase was evident in longfin eels (GSI ~ 6.9%). In addition, sex steroid and target gene mRNA levels fluctuated drastically with each hormone injection. We contend that expression of most target genes, possibly even that of cyp19a, during induced oogenesis could be “normal”, with the drastic fluctuations due most likely to hormone delivery through repeated injections. The effects of these fluctuations on gamete quality remain unknown and resolving this issue may prove fruitful in the future to further artificial propagation of anguillid eels. View Full-Text
Keywords: eel; ovarian development; steroidogenic enzyme eel; ovarian development; steroidogenic enzyme
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MDPI and ACS Style

Matsubara, H.; Lokman, P.M.; Kazeto, Y.; Okumura, H.; Ijiri, S.; Hirai, T.; Young, G.; Adachi, S.; Yamauchi, K. Changes in Sex Steroids and Ovarian Steroidogenic Enzyme mRNA Levels in Artificially Maturing Japanese Eel (Anguilla japonica) and Naturally Maturing New Zealand Longfin Eel (Anguilla dieffenbachii) during Vitellogenesis. Fishes 2019, 4, 52. https://doi.org/10.3390/fishes4040052

AMA Style

Matsubara H, Lokman PM, Kazeto Y, Okumura H, Ijiri S, Hirai T, Young G, Adachi S, Yamauchi K. Changes in Sex Steroids and Ovarian Steroidogenic Enzyme mRNA Levels in Artificially Maturing Japanese Eel (Anguilla japonica) and Naturally Maturing New Zealand Longfin Eel (Anguilla dieffenbachii) during Vitellogenesis. Fishes. 2019; 4(4):52. https://doi.org/10.3390/fishes4040052

Chicago/Turabian Style

Matsubara, Hajime, P. M. Lokman, Yukinori Kazeto, Hiromi Okumura, Shigeho Ijiri, Toshiaki Hirai, Graham Young, Shinji Adachi, and Kohei Yamauchi. 2019. "Changes in Sex Steroids and Ovarian Steroidogenic Enzyme mRNA Levels in Artificially Maturing Japanese Eel (Anguilla japonica) and Naturally Maturing New Zealand Longfin Eel (Anguilla dieffenbachii) during Vitellogenesis" Fishes 4, no. 4: 52. https://doi.org/10.3390/fishes4040052

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