Sex differentiation in pike-perch, Stizostedion lucioperca (L.)

Abstract

Morphological and histological development of gonads during the early ontogeny of pikeperch was examined. The fish were reared in fiberglass tanks and fed ad libitum with live zooplankton. Histological observations of pikeperch gonads were carried out every seven days in the period between 35 to 140 days after hatching. Body length of fingerlings at that time ranged from 3.66±0.23 to 8.92±0.28 cm, and weight ranged from 0.32±0.05 to 4.59±0.36 g. Female gonads were for the first time observed on the 126th day after hatching. No evidently male gonads were noticed during the course of the experiment. However, in some fishes smaller volume of their gonads, and fewer mitotic divisions of primordial germ cells in the gonads suggested that sex differentiation in these cases was proceeding in the male direction.