Exposure to an androgenic agricultural pollutant does not alter metabolic rate, behaviour, or morphology of tadpoles

Abstract

Globally, amphibian species are experiencing dramatic population declines, and many face the risk of imminent extinction. Endocrine-disrupting chemicals (EDCs) have been recognised as an underappreciated factor contributing to global amphibian declines. In this regard, the use of hormonal growth promotants in the livestock industry provides a direct pathway for EDCs to enter the environment—including the potent anabolic steroid 17β-trenbolone. Emerging evidence suggests that 17β-trenbolone can impact traits related to metabolism, somatic growth, and behaviour in non-target species. However, far less is known about possible effects of 17β-trenbolone on anuran species, particularly during early life stages. Accordingly, in the present study we investigated the effects of 28-day exposure to 17β-trenbolone (mean measured concentrations: 10 and 66 ng/L) on body size, body condition, metabolic rate, and anxiety-related behaviour of tadpoles (Limnodynastes tasmaniensis). Specifically, we measured rates of O2 consumption of individual tadpoles as a proxy for metabolic rate and quantified their swimming activity and their time spent in the upper half of the water column as indicators of anxiety-related behaviour. Counter to our predictions based on effects observed in other taxa, we detected no effect of 17β-trenbolone on body size, metabolic rate, or behaviour of tadpoles; although, we did detect a subtle, but statistically significant decrease in body condition at the highest 17β-trenbolone concentration. We hypothesise that 17β-trenbolone may induce taxa-specific effects on metabolic function, growth, and anxiety-related behaviour, with anurans being less sensitive to disruption than fish, and encourage further cross-taxa investigation to test this hypothesis.