Annual changes in testicular development and plasma sex steroids in the captive male dojo loach <Emphasis Type="Italic">Misgurnus anguillicaudatus</Emphasis> |
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Authors: | Solomon Kiros Jun-ya?Aoki Chang-Beom?Park Email author" target="_blank">Kiyoshi?SoyanoEmail author |
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Institution: | (1) Graduate School of Science and Technology, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan;(2) Institute for East China Sea Research, Nagasaki University, 1551-7 Taira-machi, Nagasaki 851-2213, Japan;(3) National Research Institute of Aquaculture, Tamaki Station, Fisheries Research Agency, Tamaki Mie, 519-0423, Japan;(4) Public Works Research Institute, 1-6 Minamihara, Tsukuba Ibaraki, 305-8516, Japan; |
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Abstract: | Testicular development in the captive male dojo loach Misgurnus anguillicaudatus was examined monthly in relation to the levels of plasma sex steroids testosterone (T), 11-ketotestostrone (11-KT), and
17,20β-dihydroxy-4-pregnen-3-one (DHP)]. On the basis of testicular histology, the annual gonadal cycle was found to be divisible
into 3 periods: the recovery and proliferation period, which mainly consists of early spermatogenic testis from August to
November (reproductive phase I); the preparation period for the next spawning period, which mainly consists of late spermatogenic
testis from December to April (reproductive phase II); and the mature period, characterized by a high proportion of mature
testis from May to July (reproductive phase III). Individual variability in testicular development was high, and continuous
spermatogenesis was observed throughout the year. High levels of plasma T, 11-KT, and DHP were observed during reproductive
phase III. 11-KT began to increase in February, while T was present at low levels in reproductive phase II. These results
suggest that the physiologically active season of testis development for breeding in the dojo loach is from May to July, although
spermatogenesis occurs throughout the year. |
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