Long-term exposure to environmentally relevant concentrations of diethyl phthalate alters sex ratio in Oreochromis mossambicus

The present study aimed to evaluate the effects of environmentally relevant (ER) concentrations of DEP on sex ratio of the fish Oreochromis mossambicus. Ten-day-old fry were randomly divided in to five groups: an experimental and vehicle controls and three DEP exposure groups (1, 2, and 5 µg/L) and exposed for a period of 50 days. Sex determination was assessed by observing the genital papilla and cross-sections of the gonads. The results revealed that fry exposed to 1 µg/L DEP exhibited a female-biased sex ratio, with 82.5% females and 17.5% males, whereas exposure to both 2 and 5 µg/L DEP resulted in 77.5% females and 22.5% males. In contrast, both controls exhibited an approximately balanced sex ratio (54% females and 46% males). These findings indicate that DEP exposure alters sex differentiation in fry, resulting in a higher proportion of females. These female-biased effects might be due to estrogenic-like activity of DEP.