ISSN:
1095-8649
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Testes from carp, Cyprinus carpio L., at five different maturational stages from immature through to spermiation and regression were incubated with or without addition of carp hypophysial homogenate (chh) for 8 or 20 h. Concentrations of steroids and spermatozoa were measured in the medium and the residual tissue examined histologically. There was an increase in the area of the germinal cysts containing spermatozoa, the percentage of the testis which they occupied and in the production of spermatozoa as the gonadosomatic index (GSI) increased, but this was unaffected either by incubation or by pretreatment with chh. The major steroid in plasma and in in vitro testicular cultures from all of the maturing fish captured in winter was 1 I-ketotestosterone. The production rate of this steroid in virro was unaffected by GSI, while plasma levels tended to increase with GSI. 17.20β-Dihydroxy-4-pregnen-3-one was detectable in significant amounts in only a few spermiating fish in summer, but was stimulated more in incubations with chh in maturing winter than in summer spermiating or post-spawning fish. 17,20a-Dihydroxy-4-pregnen-3-one was not detectable in incubations, but plasma concentrations tended to increase towards spermiation and were positively correlated with the size of the cyst. After spawning, fish had low plasma steroid levels and failed to respond in vitro to pituitary extract, indicating a testicular post-spawning refractoriness.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1095-8649.1990.tb05897.x
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