Reproductive toxicity of chlorpyrifos tested in zebrafish (Danio rerio) Histological and hormonal end points

This study was carried out to find out whether exposure to environmentally relevant concentration of chlorpyrifos (CP) modulates reproductive competence. To understand this, eight adult male and eight adult female zebrafish (Danio rerio) were exposed to 200 µg/L of CP for 24, 48, 72, and 96 h. Vitellogenin levels did not show much change in female fish, whereas in male the levels increased with increasing exposure time thereby indicating estrogenecity of the toxicant. Attenuation of serum 11-ketotestosterone in male and serum 17β-estradiol in female was noticed in the exposed fish and thus signified interference of CP in the reproductive endocrine system. Structural damage common to both the gonads was vacuolization. Elongation of seminiferous tubules in testes and atretic follicles in ovary was also observed.