Temperature Dependent Sex Determination In Zebrafish (Danio rerio)

Abstract

In zebrafish (Danio rerio) a polygenic pattern of sex determination or a female heterogamety with possible influences of environmental factors is assumed. The present study focuses on the effects of elevated water temperature (35°C) during the embryonic development on sex determination in zebrafish. Eggs derived from three golden (gol) females were fertilized by the same mitotic gynogenetic male and exposed to a water temperature of 35°C applied from 5-10 hpf, 5-24 hpf and 5-48 hpf, which corresponds to the following developmental stages: gastrula, gastrula to segmentation, and gastrula to pharyngula stage, respectively. Hatching and survival rates decreased with increasing exposure to high water temperatures. Reductions in the hatching and survival rates were not responsible for differences in sex ratios. Accordingly, exposition of the fertilized eggs to high temperature (35°C) lead to an increase of the male proportion from 22.0 % in the controls to a balanced sex ratio (48.3 %, 47.5 %, 52.6 %) in the gastrula, segmentation and pharyngula groups, respectively. These results prove the possibility to change the pathway of sexual determination during early embryonic stages in zebrafish by exposure to high water temperature.