Search

Amphibians are the most threatened vertebrate class globally. Multiple factors have been implicated in their global decline, and it has been hypothesized that interactions between stressors may be a major cause. Increased ultraviolet (UV) radiation, as a result of ozone depletion, has been identified as one such stressor. Exposure to UV radiation has been shown to have detrimental effects on amphibians and can exacerbate the effects of other stressors, such as chemical pollutants. Chemical pollution has likewise been recognized as a major factor contributing to amphibian declines, particularly, endocrine-disrupting chemicals. In this regard, 17 beta-trenbolone is a potent anabolic steroid used in the agricultural industry to increase muscle mass in cattle and has been repeatedly detected in the environment where amphibians live and breed. At high concentrations, 17 beta-trenbolone has been shown to impact amphibian survival and gonadal development. In the present study, we investigated the effects of environmentally realistic UV radiation and 17 beta-trenbolone exposure, both in isolation and in combination, on the morphology and behavior of tadpoles (Limnodynastes tasmaniensis). We found that neither stressor in isolation affected tadpoles, nor did we find any interactive effects. The results from our 17 beta-trenbolone treatment are consistent with recent research suggesting that, at environmentally realistic concentrations, tadpoles may be less vulnerable to this pollutant compared to other vertebrate classes. The absence of UV radiation-induced effects found in the present study could be due to species-specific variation in susceptibility, as well as the dosage utilized. We suggest that future research should incorporate long-term studies with multiple stressors to accurately identify the threats to, and subsequent consequences for, amphibians under natural conditions. Environ Toxicol Chem 2024;00:1-12. (c) 2024 The Authors. Environmental Toxicology and Chemistr

Anthropogenic sources of environmental pollution are ever-increasing as urban areas expand and more chemical compounds are used in daily life. The stimulant caffeine is one of the most consumed chemical compounds worldwide, and as a result, has been detected as an environmental contaminant in all types of major water sources on all continents. Exposure of wildlife to environmental pollutants can disrupt the energy balance of these organisms, as restoration of homeostasis is prioritised. In turn, energy allocated to other key biological processes such as growth or reproduction may be affected, consequently reducing the overall fitness of an individual. Therefore, we aimed to investigate if long-term exposure to environmentally relevant concentrations of caffeine had any energetic consequences on wildlife. Specifically, we exposed wild eastern mosquitofish (Gambusia holbrooki) to one of three nominal concentrations of caffeine (0, 100 and 10,000 ng/L) and assayed individuals for metabolic rate, general activity, antipredator and foraging behaviour and body size as measures of energy expenditure or energy intake. We found no differences in any measured traits between any of the given exposure treatments, indicating that exposure to caffeine at current environmental levels may not adversely affect the energy balance and fitness of vulnerable freshwater fish.

Temperature is a key factor mediating organismal fitness and has important consequences for species' ecology. While the mean effects of temperature on behaviour have been well-documented in ectotherms, how temperature alters behavioural variation among and within individuals, and whether this differs between the sexes, remains unclear. Such effects likely have ecological and evolutionary consequences, given that selection acts at the individual level. We investigated the effect of temperature on individual-level behavioural variation and metabolism in adult male and female Drosophila melanogaster (n = 129), by taking repeated measures of locomotor activity and metabolic rate at both a standard temperature (25°C) and a high temperature (28°C). Males were moderately more responsive in their mean activity levels to temperature change when compared to females. However, this was not true for either standard or active metabolic rate, where no sex differences in thermal metabolic plasticity were found. Furthermore, higher temperatures increased both among- and within-individual variation in male, but not female, locomotor activity. Given that behavioural variation can be critical to population persistence, we suggest that future studies test whether sex differences in the amount of behavioural variation expressed in response to temperature change may result in sex-specific vulnerabilities to a warming climate.

Lay Summary Prozac is present in freshwater systems across the globe as the pharmaceutical contaminant fluoxetine. The effect of fluoxetine on aquatic species' behavioral variability is not yet clear. We show that male guppies become more similar to each other after exposure to fluoxetine, and females become less flexible in their behavior. These sex-specific differences in response to fluoxetine can have a meaningful impact on their ability to survive in a changing world. The global rise of pharmaceutical contaminants in the aquatic environment poses a serious threat to ecological and evolutionary processes. Studies have traditionally focused on the collateral (average) effects of psychoactive pollutants on ecologically relevant behaviors of wildlife, often neglecting effects among and within individuals, and whether they differ between males and females. We tested whether psychoactive pollutants have sex-specific effects on behavioral individuality and plasticity in guppies (Poecilia reticulata), a freshwater species that inhabits contaminated waterways in the wild. Fish were exposed to fluoxetine (Prozac) for 2 years across multiple generations before their activity and stress-related behavior were repeatedly assayed. Using a Bayesian statistical approach that partitions the effects among and within individuals, we found that males-but not females-in fluoxetine-exposed populations differed less from each other in their behavior (lower behavioral individuality) than unexposed males. In sharp contrast, effects on behavioral plasticity were observed in females-but not in males-whereby exposure to even low levels of fluoxetine resulted in a substantial decrease (activity) and increase (freezing behavior) in the behavioral plasticity of females. Our evidence reveals that psychoactive pollution has sex-specific effects on the individual behavior of fish, suggesting that males and females might not be equally vulnerable to global pollutants.

Pharmaceutical pollution is a major driver of global change, with the capacity to alter key behavioural and physiological traits in exposed animals. Antidepressants are among the most commonly detected pharmaceuticals in the environment. Despite well-documented pharmacological effects of antidepressants on sleep in humans and other vertebrates, very little is known about their ecologically relevant impacts as pollutants on non-target wildlife. Accordingly, we investigated the effects of acute 3-day exposure of eastern mosquitofish (Gambusia holbrooki) to field-realistic levels (nominal concentrations: 30 and 300 ng/L) of the widespread psychoactive pollutant, fluoxetine, on diurnal activity patterns and restfulness, as indicators of disruptions to sleep. We show that exposure to fluoxetine disrupted diel activity patterns, which was driven by augmentation of daytime inactivity. Specifically, unexposed control fish were markedly diurnal, swimming farther during the day and exhibiting longer periods and more bouts of inactivity at night. However, in fluoxetine-exposed fish, this natural diel rhythm was eroded, with no differences in activity or restfulness observed between the day and night. As a misalignment in the circadian rhythm has been shown to adversely affect fecundity and lifespan in animals, our findings reveal a potentially serious threat to the survival and reproductive success of pollutant-exposed wildlife.

The progressive aridification of the Australian continent from ∼ 20 million years ago posed severe challenges for the persistence of its resident biota. A key question involves the role of refugial habitats – specifically, their ability to mediate the effects of habitat loss and fragmentation, and their potential to shape opportunities for allopatric speciation. With freshwater species, for example, the patchiness, or absence, of water will constrain distributions. However, aridity may not necessarily isolate populations if disjunct refugia experience frequent hydrological connections. To investigate this potential dichotomy, we explored the evolutionary history of the Chlamydogobius gobies (Gobiiformes: Gobiidae), an arid-adapted genus of six small, benthic fish species that exploit all types of waterbodies (i.e. desert springs, waterholes and bore-fed wetlands, coastal estuarine creeks and mangroves) across parts of central and northern Australia. We used Anchored Phylogenomics to generate a highly resolved phylogeny of the group from sequence data for 260 nuclear loci. Buttressed by companion allozyme and mtDNA datasets, our molecular findings infer the diversification of Chlamydogobius in arid Australia, and provide a phylogenetic structure that cannot be simply explained by invoking allopatric speciation events reflecting current geographic proximity. Our findings are generally consistent with the existing morphological delimitation of species, with one exception: at the shallowest nodes of phylogenetic reconstruction, the molecular data do not fully support the current dichotomous delineation of C. japalpa from C. eremius in Kati Thanda-Lake Eyre-associated waterbodies. Together these findings illustrate the ability of structural (hydrological) connections to generate patterns of connectivity and isolation for an ecologically moderate disperser in response to ongoing habitat aridification. Finally, we explore the implications of these results for the immedi