Testicular development and serum profiles of steroid hormone levels in captive male Pacific herring Clupea pallasii during their first maturational cycle |
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| Authors: | YASUNORI KOYA KIYOSHI SOYANO KAZUHISA YAMAMOTO HIROYUKI OBANA AND TAKAHIRO MATSUBARA |
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| Institution: | ;Department of Biology, Faculty of Education, Gifu University, Gifu 501-1193, ;Department of Biology, Faculty of Fisheries, Nagasaki University, Nagasaki 851-2213, ;Japan Sea-Farming Association, Akkeshi Station, Hokkaido 088-1108 and ;Hokkaido National Fisheries Research Institute, Kushiro, Hokkaido 085-0802, Japan |
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| Abstract: | The present study investigates the relationship between testicular development and serum steroid hormone levels in captive Pacific herring Clupea pallasii during the first reproductive cycle. The maturity of the testis was divided into five periods based on histological observation. These are early spermatogenic stage (April to July), mid-spermatogenic stage (August to November), late spermatogenic stage (December to March), functional maturation stage (early April) and spent stage (late April). The pattern of seasonal change in gonadosomatic index (GSI) clearly reflected testicular maturity. 11-Ketotestosterone (11-KT) levels increased from October to a peak level (6.58 ± 1.87 ng/mL) in January, and were maintained at this level until March. In contrast, testosterone levels were consistently low, less than 1 ng/mL, at all times. These results suggest that 11-KT is the predominant androgen that controls spermatogenesis in this species. 17,20β-Dihydroxy-4-pregnen-3-one (DHP) showed a single sharp peak (3.38 ± 0.35 ng/mL) in early April of the second year, suggesting that milt production is induced by DHP as in some other teleost species. |
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| Keywords: | 11-ketotestosterone 17 20β-dihydroxy-4-pregnen-3-one Pacific herring reproductive cycle testicular development testosterone |
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