Rhiannon V. Eastment

In brief: Pharmaceutical pollution can have serious consequences for wildlife reproduction. This paper reveals that exposure to the pervasive oestrogenic pollutant 17ɑ-ethinylestradiol does not impact female reproduction in a nonmodel viviparous fish. Pharmaceuticals are fast becoming a major source of environmental pollution. Many pharmaceuticals are endocrine disruptors and can thus interfere with the endocrine system of exposed organisms, leading to a suite of behavioural and physiological alterations. While numerous studies have shown that exposure to pharmaceutical contaminants can disrupt the reproductive ecology of oviparous fishes, far less attention has been given to understanding the impacts on viviparous fishes, despite their ecological and evolutionary importance. Here, we investigated the impacts of the pharmaceutical contaminant 17ɑ-ethinylestradiol (EE2) on the reproductive biology of a marine livebearer, the Southern crested weedfish (Cristiceps australis). Adult weedfish were exposed to one of three nominal concentrations of EE2 (0, 30, and 300 ng/L) for 14 days. We then assessed the impacts of exposure on morphology of both sexes, and female gametogenesis. In doing so, we found no differences in the body length, weight, or condition of fish between treatment groups. We additionally found no differences in gonadosomatic index or gametogenesis between exposed and unexposed females. In contrast to reports in other taxa, our findings suggest that short-term exposure to EE2 does not produce detectable effects on weedfish growth and reproduction. However, the extent to which exposure duration influences these responses is unknown. Ultimately, these results emphasize the importance of assessing the effects of EE2 on a diverse range of organisms if we are to gain a more comprehensive understanding of its ecological impacts.

Escalating production and consumption of medications globally has led to a sharp rise in environmental contamination with pharmaceuticals—including 17α‐ethinyl estradiol (EE2), a synthetic oestrogen used in the contraceptive pill. EE2 is now commonly detected in various ecosystems and poses risks to wildlife. Although its effects on behavioural traits are well‐documented, available data are restricted to a handful of model organisms. Therefore, the generality of such effects has not been widely considered, particularly for marine fishes. Accordingly, we investigated the effects of environmentally relevant EE2 concentrations on boldness and anxiety in a marine fish, the southern crested weedfish ( Cristiceps australis ). Weedfishes inhabit shallow coastal waters, which are often contaminated with EE2, and rely on vegetation for predator avoidance. Therefore, investigating the impact of EE2 on their refuging behaviour is critical to understanding threats to their survival. Fish were exposed for 14 days to one of three treatments: control (no added EE2), low‐dose EE2 (33 ng/L), or high‐dose EE2 (70 ng/L). Following exposure, a standard refuge‐use assay was used to assess boldness and anxiety. On the basis of observations in model species, we hypothesised that EE2 exposure would alter boldness and anxiety. Contrary to our predictions, EE2 exposure had no effect on behaviour. These findings contrast with behavioural effects reported at similar concentrations in freshwater fishes, possibly because of species‐specific physiological differences or marine environmental factors that influence the drug's uptake. Possible interspecies variability underscores the need to investigate a broader range of taxa beyond traditional ecotoxicology models to better understand EE2's ecological impact.

Background: Viviparity—live birth—is a complex and innovative mode of reproduction that has evolved repeatedly across the vertebrate Tree of Life. Viviparous species exhibit remarkable levels of reproductive diversity, both in the amount of care provided by the parent during gestation, and the ways in which that care is delivered. The genetic basis of viviparity has garnered increasing interest over recent years; however, such studies are often undertaken on small evolutionary timelines, and thus are not able to address changes occurring on a broader scale. Using whole genome data, we investigated the molecular basis of this innovation across the diversity of vertebrates to answer a long held question in evolutionary biology: is the evolution of convergent traits driven by convergent genomic changes? Results: We reveal convergent changes in protein family sizes, protein-coding regions, introns, and untranslated regions (UTRs) in a number of distantly related viviparous lineages. Specifically, we identify 15 protein families showing evidence of contraction or expansion associated with viviparity. We additionally identify elevated substitution rates in both coding and noncoding sequences in several viviparous lineages. However, we did not find any convergent changes—be it at the nucleotide or protein level—common to all viviparous lineages. Conclusions: Our results highlight the value of macroevolutionary comparative genomics in determining the genomic basis of complex evolutionary transitions. While we identify a number of convergent genomic changes that may be associated with the evolution of viviparity in vertebrates, there does not appear to be a convergent molecular signature shared by all viviparous vertebrates. Ultimately, our findings indicate that a complex trait such as viviparity likely evolves with changes occurring in multiple different pathways.