Publication Abstract

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

M. Pinillos, M.J. Delgado and A.P. Scott

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), 17,20b-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.

Reference:

M. Pinillos, M.J. Delgado and A.P. Scott, 2003. Seasonal changes in plasma gonadal steroid concentrations and gonadal morphology of male and female tench (Tinca tinca, L.). Aquaculture Research, 34(13): 1181-1189.