Express yourself: Individuals with bold personalities exhibit increased behavioral sensitivity to dynamic herbicide exposure

Population-specific responses to pollution exposure suggest local adaptation of invasive red swamp crayfish Procambarus clarkii along the Mediterranean French coastline

Anthropogenic stressors can have an impact in a broad range of physiological processes and can be a major selective force leading to rapid evolution and local population adaptation. In this study, three populations of the invasive crayfish Procambarus clarkii were investigated. They are geographically separated for at least 20 years, and live in different abiotic environments: a freshwater inland lake (Salagou lake) with no major anthropogenic influence and two other coastal wetlands regularly polluted by pesticides along the Mediterranean coast (Camargue region and Bages-Sigean lagoon). Collected adults were genetically characterized using the mitochondrial COI gene and haplotype frequencies were analyzed for genetic variability within and between populations. Results revealed a higher genetic diversity for these invasive populations than any previous report in France, with more than seven different haplotypes in a single population. The contrasting genetic diversity between the Camargue and the other two populations suggest different times and sources of introduction. To identify differences in key physiological responses between these populations, individuals from each population were maintained in controlled conditions. Data on oxygen consumption rates indicate that the Salagou and Bages-Sigean populations possess a high inter-individual variability compared to the Camargue population. The low individual variability of oxygen consumption and low genetic diversity suggest a specific local adaptation for the Camargue population. Population-specific responses were identified when individuals were exposed to a pesticide cocktail containing azoxystrobin and oxadiazon at sublethal concentrations. The Salagou population was the only one with altered hydro-osmotic balance due to pollutant exposure and a change in protease activity in the hepatopancreas. These results revealed different phenotypic responses suggesting local adaptations at the population level.

Does atrazine induce changes in predator recognition, growth, morphology, and metamorphic traits of larval skipper frogs (Euphlyctis cyanophlyctis)?

Atrazine, an info disruptor, interferes with the olfaction of aquatic organisms by impairing the chemosensory system. Consequently, it affects behavior, physiology, and growth increases mortality and infections, and suppresses the immune system of aquatic animals. In this study, we wanted to determine the sensitivity of larval Euphlyctis cyanophlyctis to different concentrations of atrazine by assessing their antipredator behavior, growth, morphology, and metamorphic traits. The results indicate that exposure to atrazine did not affect the survival of tadpoles. However, it caused retarded growth at higher concentrations. Interestingly, the antipredator behavior of tadpoles toward conspecific alarm cues decreased in a dose-dependent manner with an increase in the concentration of atrazine. Tadpoles exposed to low concentrations of atrazine had deeper, wider bodies and tails while those exposed to higher concentrations had shallower and narrower bodies with shallower tail muscles. However, at low and moderate concentrations atrazine did not affect size at metamorphosis, it extended the larval duration at higher concentrations.

Parasites differentially impact crayfish personality in different contexts

The expression of an individual animal’s behaviour can be placed along many different personality spectra. Parasite load can alter animal behaviour and, thus, fitness. The personality traits of rusty crayfish, Faxonius rusticus, were analysed in three different behavioural contexts: foraging, exploration, and threatened. Each crayfish was tested in each context 3 times, giving a total of 9 assays per crayfish. After assays were completed, crayfish were dissected, and the hepatopancreas of each crayfish was photo analysed to determine the parasite load of the trematode, Microphallus spp. A composite personality score for each assay and parasite load was loaded into a PCA. The PCA model showed that as parasite load increased, crayfish became bolder in threatening contexts and less exploratory in novel environments, whether or not a food stimulus was present. Thus, parasite load alters the placement of crayfish on different personality spectra, but this change is context specific.

Paternal exposure to a common herbicide alters the behavior and serotonergic system of zebrafish offspring

Increasingly, studies are revealing that endocrine disrupting chemicals (EDCs) can alter animal behavior. Early life exposure to EDCs may permanently alter phenotypes through to adulthood. In addition, the effects of EDCs may not be isolated to a single generation − offspring may indirectly be impacted, via non-genetic processes. Here, we analyzed the effects of paternal atrazine exposure on behavioral traits (distance moved, exploration, bottom-dwelling time, latency to enter the top zone, and interaction with a mirror) and whole-brain mRNA of genes involved in the serotonergic system regulation (slc6a4a, slc6a4b, htr1Aa, htr1B, htr2B) of zebrafish (Danio rerio). F0 male zebraFIsh were exposed to atrazine at 0.3, 3 or 30 part per billion (ppb) during early juvenile development, the behavior of F1 progeny was tested at adulthood, and the effect of 0.3 ppb atrazine treatment on mRNA transcription was quantified. Paternal exposure to atrazine significantly reduced interactions with a mirror (a proxy for aggression) and altered the latency to enter the top zone of a tank in unexposed F1 offspring. Bottom-dwelling time (a proxy for anxiety) also appeared to be somewhat affected, and activity (distance moved) was reduced in the context of aggression. slc6a4a and htr1Aa mRNA transcript levels were found to correlate positively with anxiety levels in controls, but we found that this relationship was disrupted in the 0.3 ppb atrazine treatment group. Overall, paternal atrazine exposure resulted in alterations across a variety of behavioral traits and showed signs of serotonergic system dysregulation, demonstrating intergenerational effects. Further research is needed to explore transgenerational effects on behavior and possible mechanisms underpinning behavioral effects.