Effects of environmentally-relevant concentrations of 17a- Ethinylestradiol (ee2) on non-reproductive behaviour of Danio rerio

Abstract

One of the most widely used ingredients in contraceptives is 17a-ethinylestradiol which is also known as EE2. With a half-life of 46 days, EE2 is a persistent chemical capable of resisting degradation, resulting in the prolonged exposure of aquatic ecosystems to this synthetic hormone. This study aims to determine if environmentally-relevant concentrations of 17a- ethinylestradiol (EE2) will affect the foraging, anti-predatory, exploratory, and shoaling behaviour of Danio rerio. They were exposed to different concentrations of EE2 such as 0ng/L, 2.5ng/L, 5ng/L, and 10ng/L for 21 days. To assess their foraging behaviour, the feeding latency, food intake, and growth rate were observed. Their preference on the specific quadrant in the tank as well as the tightness of their shoal were recorded. The anti-predatory behaviour was assessed through their foraging, exploratory, and shoaling behaviour. The male zebrafish had their tightest shoaling, preferred the lower quadrants, and restricted foraging activity at 10 ng/L of EE2 with a clay model of predator. Thus, these non-reproductive behaviours are sensitive indicators of EE2 exposure in zebrafish.