Antidepressants in Surface Waters: Fluoxetine Influences Mosquitofish Anxiety-Related Behavior at Environmentally Relevant Levels.

Pharmaceutical contamination is an increasing problem globally. In this regard, the selective serotonin reuptake inhibitors (SSRIs)-a group of antidepressants-are particularly concerning. By disrupting the serotonergic system, SSRIs have the potential to affect ecologically important behaviors in exposed wildlife. Despite this, the nature and magnitude of behavioral perturbations resulting from environmentally relevant SSRI exposure among species is poorly understood. Accordingly, we investigated the effects of two field-realistic levels of the SSRI fluoxetine (61 and 352 ng/L) on sociability and anxiety-related behaviors in eastern mosquitofish ( Gambusia holbrooki) for 28 days. Additionally, we measured whole-body tissue concentrations of fluoxetine and norfluoxetine. We found that fluoxetine altered anxiety-related behavior but not sociability. Specifically, female fish showed reduced anxiety-related behavior at the lower treatment level, while males showed an increase at the higher treatment level. In addition, we report a biomass-dependent and sex-specific accumulation of fluoxetine and norfluoxetine, with smaller fish showing higher relative tissue concentrations, with this relationship being more pronounced in males. Our study provides evidence for nonmonotonic and sex-specific effects of fluoxetine exposure at field-realistic concentrations. More broadly, our study demonstrated that neuroactive pharmaceuticals, such as fluoxetine, can affect aquatic life by causing subtle but important shifts in ecologically relevant behaviors.

Effects of long-term fluoxetine exposure on morphology, but not behaviour or metabolic rate, in male guppies (Poecilia reticulata).

Contamination of aquatic ecosystems by pharmaceuticals is a growing threat worldwide. The antidepressant fluoxetine is one such pharmaceutical that is frequently detected in aquatic ecosystems, and has been found to alter the behaviour and physiology of exposed wildlife. Few studies, however, have investigated potential combined effects on behaviour and metabolic rate. In addition, exposures are often short in duration and rarely conducted under ecologically relevant conditions. Here, we examined the impacts of long-term fluoxetine exposure on boldness (exploration, activity, and antipredator behaviour), metabolic rate, and morphology in male guppies (Poecilia reticulata). Specifically, fish were exposed for 8 months (corresponding to approximately two overlapping generations) in semi-natural mesocosms to one of three treatments: an unexposed control (0 ng L-1), or low or high fluoxetine (mean measured concentrations: 30 ng L-1 and 292 ng L-1, respectively). Following exposure, we quantified male exploratory behaviour and activity in a novel environment (maze arena) and antipredator behaviour in the presence or absence of a live predator (spangled perch, Leiopotherapon unicolor), as well as metabolic rate and morphology (mass, standard length, and scaled mass index). Fluoxetine exposure did not significantly alter boldness, metabolic rate, mass, or standard length. However, fluoxetine exposure did alter body condition, whereby fish in the high treatment had a higher scaled mass index than control fish. Our results, considered alongside previous work, underscore the importance of exposure duration in mediating the effects of fluoxetine on fitness-related traits. Continued research under extended exposure periods (i.e., spanning multiple generations) is essential if we are to accurately predict the ecological impacts of fluoxetine on exposed wildlife, and their underlying mechanism(s).

The endocrine disruptor 17ß-trenbolone alters the relationship between pre- and post-copulatory sexual traits in male mosquitofish (Gambusia holbrooki).

It is now well-established that reproduction in wildlife can be disrupted by anthropogenic environmental changes, such as chemical pollution. However, very little is known about how these pollutants might affect the interplay between pre- and post-copulatory mechanisms of sexual selection. Here, we investigated the impacts of 21-day exposure of male eastern mosquitofish (Gambusia holbrooki) to a field-realistic level (average measured concentration: 11 ng/L) of the endocrine-disrupting chemical 17ß-trenbolone (17ß-TB) on pre- and post-copulatory reproductive traits. We examined male reproductive behaviour by testing the time spent near a female behind a partition, as well as the number of copulation attempts made, and the time spent chasing a female in a free-swimming context. Sperm traits were also assayed for all males. We found that exposure of male fish to 17ß-TB altered the relationship between key pre- and post-copulatory reproductive traits. Furthermore, 17ß-TB-exposed males had, on average, a higher percentage of motile sperm, and performed fewer copulation attempts than unexposed males. However, there was no overall effect of 17ß-TB exposure on either the time males spent associating with or chasing females. Taken together, our findings demonstrate the potential for chemical pollutants to affect both pre- and post-copulatory sexual traits, and the interplay between these mechanisms of sexual selection in contaminated wildlife.

Impact of the widespread pharmaceutical pollutant fluoxetine on behaviour and sperm traits in a freshwater fish.

Pharmaceutical pollutants are detected in aquatic habitats and wildlife tissues globally. One widespread contaminant of major concern is the antidepressant fluoxetine, which can affect behavioural and physiological processes in non-target species. Despite this, effects of fluoxetine on wildlife behaviour have seldom been investigated across multiple fitness-related contexts, especially at environmentally realistic concentrations. Accordingly, we examined impacts of 35-day fluoxetine exposure at two environmentally relevant concentrations (31 and 374 ng/L) across a suite of fitness-related contexts in wild-caught male mosquitofish (Gambusia holbrooki). First, we investigated anxiety-related behaviours (boldness, exploration and activity) in a novel environment (maze arena) and found no significant impacts of exposure. Second, we tested effects of fluoxetine in a reproductive context, including mating behaviour and sperm quality. We found that, relative to controls, fluoxetine exposure resulted in males spending a greater amount of time pursuing females. Further, low-exposed males were more likely to attempt copulation than unexposed males. Lastly, we investigated across-context behavioural correlations, and how fluoxetine exposure might affect such relationships. A significant positive correlation was detected in control fish between activity levels in the maze and time spent pursuing females in the reproductive assay. This relationship was disrupted by fluoxetine at both exposure levels. This is the first evidence that field-detected concentrations of a pharmaceutical pollutant can disturb across-context behavioural correlations in wildlife. Our findings provide clear evidence that fluoxetine can produce context-specific behavioural effects in fish and underscore how pharmaceutical exposure at field-detected concentrations can induce important shifts in wildlife behaviour.