Sex in troubled waters: The impact of trenbolone on sexual selection in a freshwater fish (#435)
Sexual selection and female mate choice are particularly sensitive to human-induced environmental change. It has been well established that changes to the visual and acoustic environment can affect the ability of females to choose mates, however the consequences of altering the chemical environment are relatively unknown. Endocrine disrupting chemicals (EDCs) are one group of chemical contaminants with the ability to disrupt sexual selection. A recent surge in interest towards behavioural studies has revealed that EDCs can impact a wide range of behaviours, but their effect on sexual selection and female mate choice is poorly understood. Further, the majority of behavioural ecotoxilogical studies have focused on only one group of EDCs (i.e. those with estrogenic properties) while comparatively little is known about the behavioural impact of androgenic EDCs. One androgenic EDC with the potential to affect sexual selection is the androgenic steroid, trenbolone. Trenbolone is a particularly potent compound used to promote growth rates in beef cattle around the world, and has been detected in waterways associated with cattle feedlots. It is known to cause severe morphological and physiological abnormalities, but its impact on sexual selection has yet to be investigated. To address this gap in the literature, we investigated the impact of an environmentally relevant concentration of trenbolone on female mate choice in the guppy (Poecilia reticulata). When given a choice between trenbolone-exposed and unexposed males, unexposed females were found to prefer unexposed males. However, trenbolone-exposed females showed no preference for either male, suggesting they had lost the ability to discern between males of differing quality. Considering female mate choice plays a pivotal role in maintaining the genetic fitness of a population, the disruption of these mechanisms could have far reaching evolutionary consequences. This is one of the few studies to show that an androgenic EDC can influence female reproductive behavior, and the first to show that androgenic EDC exposure can affect sexual selection and female mate choice.