Effect of Cadmium Chloride on Maturity of Female Zebrafish (Danio rerio) using Vitellogenin Biomarker and Ovary Histopathology

This study aimed to investigatethe changes in Gonad Somatic Index (GSI), vitellogenin induction and ovarian histopathology in zebrafish (Danio rerio) adult female, as an ecological model in toxicology, after exposure to 0.002, 0.02, 0.2, 2 and 20 µg/L cadmium chloride for 21 days under sub-lethal condition. The results showed that 0.002 to 20 µg/L cadmium chloride had no significant effect on the survival, But GSI and vitellogenin concentrations in whole body homogenate (WBH) decreased in a dose- dependent manner in all treatments. Gonad histology showed increased proportion of atretic follicles, reduced proportion of vitellogenic oocytes, haemorrhage, hyperemia, membrane folding in some oocytes, hypertrophy of granulosa cells, proteinaceous fluid and decreased yolk formation in vitellogenic oocytes. These changes indicate a disturbed reproductive output. The results of this study showed that an increase in atretic follicles and decreased vitellogenin have negative effects on zebrafish fertility. Moreover,continuous exposure to subacute sublethal concentrations of cadmium chloride had anti-estrogenic and irreversible effects on zebrafish reproduction.