Steroid profiles in cultured female jundia, the siluridae Rhamdia quelen (Quoy and Gaimard, Pisces Teleostei), during the first reproductive cycle

The jundia Rhamdia quelen (Quoy and Gaimard) is a teleost species from the Siluridae family and is an important species for aquaculture in temperate and subtropical climates. Gonad and blood tissue samples were taken from cultured jundia females between 1998 and 1999, Plasma concentrations of 17 beta -estradiol (E-2), testosterone (T), 11-ketotestosterone (11-KT), 17-hydroxy-4-pregnene-3,20-dione (17-P), 17,20 beta -dihydroxy-4-pregnen-3-one (17,20 beta -P), and 17,20 beta ,21-trihydroxy-4-pregnen-3-one (20 beta -S) were measured by radioimmunoassay and potential correlations with the stage of oogenesis and sexual maturation examined. During the experimental period two spawning episodes were observed, Plasma concentrations of E-2 increased progressively during oocyte development, simultaneously with the appearance of yolk vesicles and increasing amounts of deposited yolk. In female jundia, the T peak occurred in October and was coincident with the peak in gonadosomatic index. Two distinct peaks of progestogens were detected, correspending to the two spawning episodes, suggesting that one or more of these steroids might act as the "maturational-inducing steroid" in jundia. Unusually large amounts of 11-KT were also measured in the plasma of mature jundia females. The identity of 11-KT was confirmed by thin-layer chromatography, Although the profiles of the other steroids are compatible with the roles proposed for the action of these hormones in other teleosts, the role of 11-KT, normally found only in males, is unknown. (C) 2001 Academic Press.