Correlation between plasma levels of sex steroids and spermatogenesis during the sexual cycle in the chub, Leuciscus cephalus L. (Pisces: Cyprinidae)

Correlations between plasma levels of sex steroids and spermatogenesis during the sexual cycle of the chub, Leuciscus cephalus L. (Pisces, Cyprinidae). Zoological Studies 44(2): 228-233. Analyses of biometric data, plasma steroids levels, and gonadal morphology allowed us to define the sexual cycle of the cyprinid fish, the chub, Leuciscus cephalus, which is widely distributed in European rivers. Four physiological gonadal phases were defined: 1) stasis (Dec.~Feb.); 2) recovery (Mar.~Apr.); 3) spawning (May~June); and 4) post-spawning (July~Nov.). Specific changes in plasma sex hormone levels were found to occur during the different phases of gonadal development. Plasma androgen levels presented a biphasic profile, with peaks corresponding to the end of the stasis phase (Feb.) and during the spawning phase (June). High levels of estradiol-17β were detectable from the early recovery phase (Apr.) to the late spawning phase (June). Their possible roles in gonadal activity are discussed and compared with observations on reproduction in the chub in other areas of their European distribution.