Journal of experimental zoology. Part A, Ecological and integrative physiology最新文献

Stress during development can elicit lifelong changes to an organism. However, whether these changes are beneficial or detrimental can only be determined by their effect on fitness outcomes. Furthermore, the effect of severe, chronic food restriction on the development of ornamentation, which can influence attractiveness, still needs to be explored. In this study, zebra finches (Taeniopygia castanotis) were exposed to either an ad libitum (control) diet or a 40% restricted (food-restricted) diet throughout postnatal development. Pictures of beaks and cheek patches were captured throughout the juvenile period and into adulthood to measure the development of secondary sexual characteristics. In adulthood, females were paired with nonexperimental males to measure reproductive success. There was no effect of treatment on beak color development or final beak color, but food-restricted males developed cheek patches slower and had more asymmetry during cheek patch development. However, food restriction did not impact the final cheek patch color or size. Food-restricted females were found to have lower reproductive success than control females. These results suggest that while cheek patch ornamentation can experience 'catch-up growth', and beak and cheek patch color do not reflect past developmental stress exposure, developmental food restriction impairs female reproductive success in a short-lived passerine.

Water availability has critical impacts on numerous physiological functions in all organisms and can have different effects across life stages. For example, water available to reproductive females can influence offspring production, and has the potential to influence how early-stage offspring (e.g., embryos) respond to moisture in their developmental environment. In this study, we use the brown anole lizard (Anolis sagrei) to examine the effects of water availability on reproductive investment. We tested the hypothesis that water available to mothers influences embryonic development under different levels of moisture in their incubation environment. We demonstrate that a substantial reduction in water availability to mothers (~70% reduction) has no observable effect on fecundity, egg size, or egg hydration. We also provide evidence that our water restriction to mothers does not influence how embryos respond to moisture conditions during egg incubation. However, moisture in the egg incubation substrate positively affected egg water uptake, egg hatching success and hatchling body size (but not hatchling hydration). Overall, our study shows that reproduction in adult female A. sagrei is robust to variation in water availability, but survival during early life stages is sensitive to this variable. Thus, the effect of water availability on different fitness components varies between life stages.

Escape responses are vital for the survival of prey. The high speeds and accelerations needed to evade predators successfully require exerting forces on the environment. Unlike water, terrestrial habitats can vary in ways that constrain the forces applied, requiring animals to adjust their behavior in response to variable conditions. We evaluated the terrestrial jumping of an amphibious fish, the blackspotted rockskipper (Entomacrodus striatus), to determine if substrate roughness and wetness influence jumping performance. We predicted that rockskippers would produce a greater force output as substrate roughness increased and wetness decreased. Using a novel waterproof force plate capable of detecting millinewton loads, we collected ground reaction forces from rockskippers jumping on wet and dry sandpapers of varying grits. We also used micro-CT scans to quantify muscle mass as a relative fraction of body mass to determine if these jumps could be performed without power amplification. Mixed-model analysis of jumps revealed significantly higher maximum horizontal forces, jump duration, and maximum power on dry versus wet substrates, but no effect of substrate roughness. However, the final jump outcomes (takeoff speed and angle) were unaffected. Peak jump power was within the range of typical fish muscle. Thus, these fish display a jumping behavior which is robust to substrate property variation.

Artificial light sources, particularly blue light, have raised concerns about their impact on biological health and behavior. In this study, we explored the effects of blue light on the locomotion and cognitive functions of early adult Drosophila melanogaster. Our experiments were conducted in a custom-designed behavioral arena to assess how blue light influences these parameters. We found that after ~2 weeks of blue light exposure, the locomotion of fruit flies, including movement speed and activity levels, significantly increased, but these effects disappeared by the third week. However, this exposure also led to a notable reduction in lifespan and had adverse effects on cognitive functions, including attention and short-term spatial memory. These findings may reveal the profound impacts of blue light on neural behavioral functions and lifespan, highlighting the importance of further research into the biological effects of blue light.

Mice in the genus Peromyscus are abundant and geographically widespread in North America, serving as reservoirs for zoonotic pathogens, including Borrelia burgdorferi (B. burgdorferi), the causative agent of Lyme disease, transmitted by Ixodes scapularis ticks. While the white-footed mouse (Peromyscus leucopus (P. leucopus)) is the primary reservoir in the United States, the deer mouse (P. maniculatus), an ecologically similar congener, rarely transmits the pathogen to biting ticks. Understanding the factors that allow these similar species to serve as a poor and competent reservoir is critical for understanding tick-borne disease ecology and epidemiology, especially as climate change expands the habitats where ticks can transmit pathogens. Our study investigated immunological differences between these rodent species. Specifically, we compared the expression of six immune genes (i.e., TLR-2, IFN-γ, IL-6, IL-10, GATA-3, TGF-β) broadly involved in bacterial recognition, elimination, and/or pathology mitigation in ear biopsies collected by the National Ecological Observatory Network (NEON) as part of their routine surveillance. A principal components analysis indicated that immune gene expression in both species varied in two dimensions: TLR2, IFN-γ, IL-6, and IL-10 (comprising PC1) and TGF-β and GATA3 (comprising PC2) expression tended to covary within individuals. However, when we analyzed expression differences of each gene singly between species, P. maniculatus expressed more TLR2, IL-6, and IL-10 but less IFN-γ and GATA3 than P. leucopus. This immune profile could partly explain why P. leucopus is a better reservoir for bacterial pathogens such as B. burgdorferi.

The open field test (OFT) is frequently used in research to assess anxiety-like behavior and locomotor activity. Its simple design can lead to the misconception that it is a standardized procedure comparable between laboratories. However, some modifications in the setup can cause changes in behavior. Different species might also react differently to the modifications introduced. There is thus need for a better understanding of the impact of modifications and their value for the species in question. Here, we tested two closely related mouse species, Mus musculus and Mus spretus, in an OFT with and without the presence of a shelter. We assessed mouse exploratory behavior through the analysis of multiple behavioral traits, and stress response through the measurement of circulating cortisol levels. Both species had elevated cortisol levels during the OFT in contrast to control animals which were not exposed to the OFT. While the presence of a shelter in the OFT increased the exploratory behavior in both mouse species, M. spretus, but not M. musculus, showed a reduction in cortisol levels. Also, other measured behaviors show a rather proactive coping strategy of the commensal M. musculus in contrast to a reactive strategy of the non-commensal M. spretus. Our study revealed a strong species-specific influence of the OFT design on the resulting behavior and stress levels of mice, illustrating the importance of OFT designs to account for the characteristics of the species under study. The addition of a shelter might be considered to improve experimental results by promoting animal welfare.

Noninvasive evaluations of hormones can contribute to the assessment of health and welfare of animals. Variations in insulin levels and sensitivity, for example, have been linked to health concerns in non-human and human primates including insulin resistance, diabetes, and heart disease, the leading cause of death in zoo-housed gorillas. Few published studies have assessed insulin concentrations in western lowland gorillas (Gorilla gorilla gorilla), and all did so using serum. Anesthesia is typically required to collect blood samples from zoo-housed gorillas, limiting sampling frequency and restricting samples to the fasted state. The ability to measure insulin levels in saliva would eliminate these constraints and provide a minimally invasive means for monitoring this hormone. The purpose of this study was to analytically and biologically validate the measurement of insulin in saliva of western lowland gorillas using a commercially available enzyme immunoassay. For validation, an oral sugar test was conducted on five adult gorillas residing at Cleveland Metroparks Zoo. Such assessments are common practice in both human and equine medicine to evaluate the body's insulin response to ingestion of sugars. The test involved measuring salivary insulin at timed intervals before and after gorillas consumed doses of sugar. Salivary insulin levels increased from 15 min post-sugar ingestion and peaked after 90 to 120 min. One female had a high response and peaked at 990.21 mU/L. The other four gorillas had peaks between 49.82 and 167.04 mU/L. The assessment provided a biological validation for the measurement of salivary insulin in western lowland gorillas.

Gastrointestinal infections present major challenges to ruminant livestock systems, and gut health is a key constraint on fitness, welfare, and productivity. Fecal biomarkers present opportunities to monitor animal health without using invasive methods, and with greater resolution compared to observational metrics. Here we developed enzyme-linked immunosorbent assays for three potential fecal biomarkers of gut health in domestic ruminants: two immunological (total immunoglobulin [Ig]A and total IgG) and one inflammatory (lactoferrin). We analytically validated the assays, then evaluated whether they could be used as a biomarker of clinically diagnosed gastrointestinal pathologies in cattle (Bos taurus), and finally compared them with helminth fecal egg counts in sheep (Ovis aries). The analytes were detected above the lower limits of detection in cattle, sheep, and goats. Fecal IgA and lactoferrin were higher in cattle with infectious pathologies (strongyles, coccidiosis and symptomatic Johne's disease) compared to healthy controls. Lactoferrin was additionally higher in animals with infectious pathologies compared to noninfectious pathologies, and to asymptomatic Johne's cases. No significant relationships were found with sheep fecal egg counts. These initial findings suggest that fecal IgA and lactoferrin may be useful biomarkers of poor gastrointestinal health in cattle, and that fecal lactoferrin is specific to active inflammation caused by infectious agents. These could be incorporated into the growing suite of noninvasive ecoimmunological tools and used to understand ruminant gut health in a range of species. Applications include improving treatment regimens for gastrointestinal infections, and understanding wildlife physiological responses to infectious challenges.

Exposure of avian mothers to stressful conditions permanently alters offspring behavior and physiology. Yet, the effects of maternal stress on the development of offspring immunity in birds remain unclear, particularly in wild species. We injected Eastern bluebird (Sialia sialis) eggs with either a corticosterone or control solution, then measured the impacts on nestling morphology and two measures of immunity, bactericidal capacity and swelling responses to phytohemagglutinin. Nestlings from corticosterone-treated eggs had lower condition indices at hatch but quickly caught up to their control counterparts by Day 5 posthatch and until fledging. Corticosterone-exposed nestlings also mounted smaller swelling responses to phytohemagglutinin, whereas there were no effects on bactericidal capacity. These results indicate that maternal stress can impact offspring immunocompetence, fitness prospects, and potentially their ability to fend off parasites and pathogens.

In the wild, stressors occur with varying likelihood throughout the day, leading animals to evolve plastic stress responses that exhibit circadian rhythmicity. In mammals, studies have revealed that the circadian plasticity of stress response may differ with age. However, such developmental effects have been largely overlooked in other vertebrate groups. In our research, we explored the presence of developmental variation in the daily pattern of behavioral stress response in a teleost fish model: the zebrafish (Danio rerio). We compared juvenile and adult individuals in two behavioral paradigms commonly used to analyze fish stress response, such as the open-field test and the diving test. Our comparisons were conducted every 4 h during a 24-h cycle to analyze daily variations. Significant daily rhythms were detected for almost all analyzed behaviors in both tests. In general, the analyses suggested a greater stress response in adults during the daytime and in juveniles during the night-time, although not all indicators aligned in this direction. Moreover, we found average differences in zebrafish behavior, suggesting that juveniles were more sensitive to stress. Overall, these findings highlight the importance of considering developmental variation in the circadian pattern of stress response in non-mammalian species like zebrafish.