Sex differences in the predictability of risk-taking behavior.

Recent research has found that individuals often vary in how consistently they express their behavior over time (i.e., behavioral predictability) and suggested that these individual differences may be heritable. However, little is known about the intrinsic factors that drive variation in the predictability of behavior. Indeed, whether variation in behavioral predictability is sex-specific is not clear. This is important, as behavioral predictability has been associated with vulnerability to predation, suggesting that the predictability of behavioral traits may have key fitness implications. We investigated whether male and female eastern mosquitofish (Gambusia holbrooki) differed in the predictability of their risk-taking behavior. Specifically, over a total of 954 behavioral trials, we repeatedly measured risk-taking behavior with three commonly used assays-refuge-use, thigmotaxis, and foraging latency. We predicted that there would be consistent sex differences in both mean-level risk-taking behavior and behavioral predictability across the assays. We found that risk-taking behavior was repeatable within each assay, and that some individuals were consistently bolder than others across all three assays. There were also consistent sex differences in mean-level risk-taking behavior, with males being bolder across all three assays compared to females. In contrast, both the magnitude and direction of sex differences in behavioral predictability were assay-specific. Taken together, these results highlight that behavioral predictability may be independent from underlying mean-level behavioral traits and suggest that males and females may differentially adjust the consistency of their risk-taking behavior in response to subtle changes in environmental conditions.

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

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 17ß-trenbolone. Emerging evidence suggests that 17ß-trenbolone can impact traits related to metabolism, somatic growth, and behaviour in non-target species. However, far less is known about possible effects of 17ß-trenbolone on anuran species, particularly during early life stages. Accordingly, in the present study we investigated the effects of 28-day exposure to 17ß-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 17ß-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 17ß-trenbolone concentration. We hypothesise that 17ß-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.

Lizard reproductive biology beyond the gonads: An investigation of sperm storage structures and renal sexual segments.

In this study, we investigated the reproductive biology of the small lizard Eurolophosaurus nanuzae based on evidence of sperm storage by females and variations of the renal sexual segment (RSS) in males. We found a remarkable occurrence of crypts containing bundles of sperm and secretions in the epithelium of E. nanuzae oviducts. The chemical composition of the secretions associated with the sperm within the crypts was similar to secretions from the oviductal epithelium, which suggests that females can produce substances involved in the maintenance of stored sperm. Female sperm storage does not occur over the span of years for long-term reproduction; the majority of females with stored sperm occurred during the peak and late periods of the reproductive season. We discuss this result in relation to post-copulatory sexual selection strategies in the context of sperm competition for restricted successful fertilisation. In males, testicular activity was continuous, while RSS activity varied seasonally, in synchrony with female reproductive activity. Throughout the reproductive season, the RSS was hypertrophied, with maximum activity during the peak of the reproductive season. The lowest RSS activity occurred when females were not reproductive (non-reproductive season). Considering that RSS secretions are essential for reproduction, an absence or reduction of these secretions during the non-reproductive season may imply the reduced functionality of sperm during this period. Since sperm production continues throughout the whole reproductive cycle in E. nanuzae males, RSS activity could be an important indicator of reproduction, beyond testicular activity.

Helminths infection patterns in a lizard (Tropidurus hispidus) population from a semiarid neotropical area: associations between female reproductive allocation and parasite loads.

This study reports helminth infection patterns of the lizard Tropidurus hispidus from an area of semiarid caatinga in northeastern Brazil (Ceará state). The lizard population was parasitized by 8 helminth species, and the species composition of the component community resembles that found for other Neotropical lizards. The prevalence of parasites was higher for males compared with females, whereas no relation was found between intensity of infection of 2 parasites (Parapharyngodon alvarengai and Physaloptera lutzi) and the lizards body size. For reproductive females, parasite infection intensity was negatively correlated to reproductive investment.

Cannabinoid type-1 receptor ligands, alone or in combination with cocaine, affect vigilance-related behaviors of marmoset monkeys.

Endocannabinoids (eCB) have been functionally linked to cocaine׳s rewarding effects. However, results differ at the behavioral level, with few reports in nonhuman primates (NHPs). Here we analyzed whether repeatedly administered cannabinoid type-1 receptor (CB1r) agonist WIN 55-212,2 (WIN) or antagonist AM 251 (AM) induce effects per se and if concurrent pre-treatments affect cocaine-induced changes in marmoset behavior. Six groups were tested: WIN-saline; WIN-cocaine; AM-saline; AM-cocaine; vehicle-cocaine; and vehicle-saline. Subjects were pre-treated with either WIN (1mg/kg), AM (2mg/kg) or vehicle and then injected with cocaine (5mg/kg) or saline. Six exposures were held at 48 h intervals. Behaviors were scored during 15-min in an open-field on days 1 and 6, as well as a withdrawal (WD) trial. Marmosets became hypervigilant during cocaine exposures, which did not condition to the injection context. CB1r activation induced an equivalent response, whereas AM had no effect on its own. However, when given as a pre-treatment to cocaine, CB1r blockade enhanced the former׳s hypervigilance effect and potentially conditioned this response to the exposure context. Enhancement may have resulted from AM׳s inhibition of eCB-potentiated cocaine-induced anxiogenesis and/or its action independent of the eCB system, or even CB1r-mediated changes in synaptic plasticity involved in cocaine reward-learning. All effects were independent of motor function. Thus, changes in CB1r function - alone and in combination with cocaine - affected stereotyped vigilance-related behaviors in this NHP, further implicating the eCB system in the neurobiological mechanisms of cocaine addiction.

Repeated cocaine administration in marmoset monkeys induces hypervigilance-related behaviors, but no changes in locomotion and cortisol levels.

Although cocaine induces several behavioral and hormonal effects, little is known about non-contingent repeated administrations in non-human primates. Therefore, we analyzed behavioral (locomotion, vigilance) and hormonal (cortisol) responses of adult black tufted-ear marmosets during repeated administrations and withdrawal trials. The subjects were divided into two groups (saline or cocaine 5mg/kg, ip) and submitted to nine treatment trials and four withdrawal trials in the absence of any treatment in an open-field arena. Blood samples were obtained on five different time points of the procedure to evaluate the effects of repeated cocaine treatment on basal cortisol levels. Cocaine repeatedly administered to drug-naïve marmosets induced a slow-onset hypervigilance effect (i.e., scan - long-lasting sweeping movements of the head directed at the environment; and glance - single rapid movement of the head directed at the environment), with no concomitant change in locomotion. Treatment cessation during withdrawal immediately reversed the cocaine-induced hypervigilance effect. Cortisol levels remained constant throughout the procedure. Therefore, marmosets seem to have a similar behavioral - but not hormonal - response as humans and other nonhuman primates repeatedly injected with cocaine, but differ from rats in their absence of hyperlocomotor activity. The development of hypervigilance with repeated application may constitute a unique measure to assess cocaine-induced changes in behavior in the marmoset and other nonhuman primates.

Diazepam-induced decrease in anxiety-like behaviors of marmoset monkeys exposed to a novel open-field.

Unfamiliar environments can be a source of stress, fear and anxiety for marmoset monkeys. In spite of existing data, the influence of putative anxiolytics on the effects of novel environments has yet to be tested in primates. Therefore, the behavior of adult black tufted-ear marmosets to a single brief (15 min) exposure to a novel environment was analyzed in the presence and absence of diazepam (DZP). Marmosets were pre-treated with vehicle (n=5) or diazepam (0.5 mg/kg, ip; n=5) and submitted to a 15 min free exploration trial within a rectangular open-field arena. DZP-treated subjects, compared to vehicle controls, demonstrated significantly lower rates of (phee) contact calls and exploration, while a higher scan duration. Sojourn time in the arena's central zone was also significantly higher in the former group and sedation was not observed. Thus, pre-treatment with the benzodiazepine DZP decreased several anxiety-related behaviors induced by subjecting the marmosets to a new environment. The results also indicate that, as with rodent subjects, the open-field may provide a useful simple paradigm for assessing anxiety-like behaviors in this primate and, as such, constitutes a unique opportunity for direct comparative studies between rodents and marmoset monkeys in terms of anxiety and/or sedation.