Chronic exposure to 17α-ethinylestradiol reduces behavioral consistency in male Siamese fighting fish

Abstract

Both acute and chronic exposure to 17α-ethinylestradiol (EE2), one of the primary active ingredients of birth control pills, decreases courtship and aggression in males of aquatic species. However, how exposure affects behavioral consistency over time is not commonly addressed. To examine the effects of chronic EE2 exposure on behavioral consistency, adult male Siamese fighting fish, Betta splendens, received multiple trials with a dummy male and dummy female presented simultaneously both before and after chronic exposure to a nominal dose (10 ng/l) of EE2. The responses of exposed males were compared before and after exposure and against those of a group of unexposed, control males. Male-directed and female-directed behaviors were reduced after 28 days of EE2 exposure. More importantly, chronic EE2 exposure had dramatic effects on consistent individual differences in female-directed and male-directed behaviors. Repeatability values were markedly lower and level of response was less correlated in the EE2 group, suggesting that exposure disrupts both between-individual variation and behavioral consistency. These results cannot be explained by a temporal effect as they were not found in the control group of unexposed males. This study demonstrates that EE2 exposure may have effects beyond a reduction in overall response. It also demonstrates the importance of studying the effects of chemical exposure on multiple time scales as acute exposure to EE2 affects the consistency of only female-directed behaviors in this species whereas chronic exposure affects consistency of both female-directed and male-directed behavior. Finally, this study suggests that males in this species may differ in their sensitivity, an important area for future research.