Seasonal changes in plasma gonadal steroid concentrations and gonadal morphology of male and female tench (Tinca tinca, L.)

M.L. Pinillos, M.J. Delgado, A.P. Scott-2003

Aquaculture Research, 34(13): 1181-1189
Abstract:

In order to gain a better understanding of the reproductive cycles of male and female tench (Tinca tinca), gonadosomatic index, gonad histology and plasma concentrations of estradiol-17β (E₂), testosterone, an drostenedione, 11-ketotestosterone (11-KT), 17,20β, 21-trihydroxy-4-pregnen-3-one (17,20β,21-P), 17,20β -dihydroxy-4-pregnen-3-one (17,20β -P) and 17,20α-dihydroxy-4-pregnen-3-one (17,20α-P) were measured at the four seasons of the year, plus a further sampling coincident with the peak of spawning in early July. As expected, in both males and females, the plasma concentrations of androgens (excluding 11-KT in females - undetectable) and C₂₁ steroids were significantly more elevated in the spring and summer (when most gonadal development took place) than in the autumn and winter. The only unexpected finding was that 17,20β -P and 17,20β,21-P, the steroids that are normally associated with oocyte final maturation in females and spermiation in males, were found in substantial amounts in both pre-vitellogenic, pre-spermatogenic and post-spawning fish. This suggests that these steroids may have other as yet unidentified roles in this species.

(Departamento de Fisiología (Fisiología Animal), Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain. E-mail of M.J. Delgado: mjdelgad@bio.ucm.es)

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