Cytogenotoxic stress response in cave-dwelling bats: a pilot study from Vietnam.

The DNA replication stress (RS) response is crucial for maintaining cellular homeostasis and promoting physiological longevity. However, the mechanisms by which long-lived species, such as bats, regulate RS to maintain genomic stability remain unclear. Also, recent studies have uncovered noncanonical roles of ribosome-associated factors in maintaining genomic stability. In this study, somatic skin fibroblasts from the long-lived big-footed bat (Myotis pilosus) were examined, with results showing that bat cells exhibited enhanced RS tolerance compared to mouse cells. Comparative transcriptome analysis under RS conditions revealed pronounced species-specific transcriptional differences, including robust up-regulation of ribosome biogenesis genes in bat cells and a markedly reduced activation of the P53 signaling pathway. These features emphasize a distinct homeostatic strategy in bat cells. Nuclear fragile X mental retardation-interacting protein 1 (Nufip1), a ribosome-associated factor highly expressed in bat fibroblasts, was identified as a potential integrator of ribosomal and P53 signaling via its association with ribosomal protein S27-like (Rps27l). These findings provide direct cellular and molecular evidence for a noncanonical RS response in bats, highlighting a deeper understanding of the biological characteristics and genomic maintenance mechanisms of long-lived species.

Studies were conducted to assess the response of a seasonal cave-dwelling bat and its insect prey to natural and experimental changes in barometric pressure. The Eastern Pipistrelle, Pipistrellus subflavus, tracks barometric pressure metabolically. Eastern Pipistrelles potentially use pressure as a cue for predicting the relative abundance of aerial insect prey outside the roost. Barometric pressure tracking affords these bats an opportunity to conserve limited energy and make appropriate foraging decisions. Barometric pressure tracking is viewed as an alternative evolutionary strategy to torpor and may be a widespread phenomenon among insect-feeding bats that roost deep within caves.

Behavioral responses of cave-roosting bats to artificial light of different spectra and intensities: Implications for lighting management strategy

Urban environments alter various physiological responses of sympatric animals. In this chapter, we provide an overview of stress physiology and the responses of bats to different urban stressors, such as light and noise pollution. We suggest future directions of research connecting urbanisation and stress responses of bats, whose life history traits determine an idiosyncratic response to urbanisation. We review how foraging behaviour and the physiological ecology of bats vary with the urban environment and present data on the effect of roost microclimate on metabolism and water balance of bats. We discuss these findings under an evolutionary lens and conclude that synanthropic species of bats possess preadaptations. These adaptations include resilience to urban stressors, fast flight, use of sheltered roosts, and relatively low metabolic rates to survive and thrive in urban habitats.

Critical roles of mitochondria in brain activities of torpid Myotis ricketti bats revealed by a proteomic approach

Little is known about to what extent the sensitivity of the hypothalamic-pituitary-adrenal (HPA) axis may be state dependent and vary in the same species between environments. Here we tested whether the faecal corticosteroid concentrations of matrilineal adult female spotted hyenas are influenced by social and reproductive status in adjacent ecosystems and whether they vary between periods with and without social stress. Females in the Serengeti National Park frequently become socially subordinate intruders in other hyena territories by undertaking long-distance foraging trips to migratory herds, whereas in the Ngorongoro Crater they usually forage inside their own small territories on resident prey. The faecal corticosteroid concentrations in Serengeti females were significantly higher than in Ngorongoro females. Energy expenditure by lactation is exceptionally high in spotted hyenas and this may be reflected in their corticosteroid levels. The faecal corticosteroid levels in both populations were higher in lactating than in non-lactating females. During periods of social stability, faecal corticosteroid concentrations increased in non-lactating females but not in lactating females as social status declined. Lactating Serengeti females had significantly higher faecal corticosteroid concentrations during periods with acute severe social stress than during periods without, indicating that the HPA axis is sensitive to social stimuli even in lactating females. So far few studies have used non-invasive monitoring methods for assessing social stress in freeranging animals. This study demonstrates for the first time, to the authors' knowledge, that corticosteroid concentrations may differ between periods with and without social stress for a free-ranging female mammal and that the modulating effect of social status may depend on reproductive status.

Changes in reproductive state or the environment may affect the sensitivity of the hypothalamic-pituitary-andrenal (HPA) axis. However, little is known about the dynamics of the resulting corticosteroid stress response, in particular in tropical mammals. In this study, we address the modulation of corticosterone release in response to different reproductive conditions and seasonality in 326 free-living common fruit-eating bats (Artibeus jamaicensis) on Barro Colorado Island in Panama during dry and wet seasons. We present strong evidence that stress sensitivity is primarily modulated by reproductive condition. In reproductively active females, corticosterone increases were more rapid and reached higher levels, but also decreased significantly faster than in inactive females. The corticosterone response was weaker in reproducing males than in females and delayed compared to non-reproductive males. Testes volume in reproductively active males was negatively correlated with corticosterone concentrations. Our findings suggest differentiated dynamics in the corticosterone stress response between sexes, potentially reflecting conflicting ecological demands. In females, a strong acute corticosterone response may represent high stress- and risk-sensitivity that facilitates escape and thus helps to protect reproduction. In males, suppression during reproductive activity could reflect lowered stress sensitivity to avoid chronically elevated corticosterone levels in times of frequent aggressive and therefore costly inter-male encounters.

Environmental and biological context play significant roles in modulating physiological stress responses of individuals in wildlife populations yet are often overlooked when evaluating consequences of human disturbance on individual health and fitness. Furthermore, most studies gauge individual stress responses based on a single physiological biomarker, typically circulating glucocorticoid concentrations, which limits interpretation of the complex, multifaceted responses of individuals to stressors. We selected four physiological biomarkers to capture short-term and prolonged stress responses in a widespread cave-roosting bat, Hipposideros diadema, across multiple gradients of human disturbance in and around caves in the Philippines. We used conditional inference trees and random forest analysis to determine the role of environmental quality (cave complexity, available roosting area), assemblage composition (intra- and interspecific associations and species richness), and intrinsic characteristics of individuals (sex and reproductive status) in modulating responses to disturbance. Direct cave disturbance (hunting pressure and human visitation) was the primary driver of neutrophil-to-lymphocyte ratios, with lower ratios associated with increased disturbance, while context-specific factors were more important in explaining total leukocyte count, body condition, and ectoparasite load. Moreover, conditional inference trees revealed complex interactions among human disturbance and modulating factors. Cave complexity often ameliorated individual responses to human disturbance, whereas conspecific abundance often compounded responses. Our study demonstrates the importance of an integrated approach that incorporates environmental and biological context when identifying drivers of physiological responses, and that assesses responses to gradients of direct and indirect disturbance using multiple complementary biomarkers.

Recently bats have been associated with the emergence of diseases, both as reservoirs for several new viral diseases in humans and other animals and, in the northern Americas, as hosts for a devastating fungal disease that threatens to drive several bat species to regional extinction. However, despite these catastrophic events little Information is available on bat defences or how they interact with their pathogens. Even less is known about the response of bats to infection during torpor or long-term hibernation. Using tissue samples collected at the termination of an experiment to explore the pathogenesis of White Nose Syndrome in Little Brown Bats, we determined if hibernating bats infected with the fungus Pseudogymnoascus destructans could respond to infection by activating genes responsible for innate immune and stress responses. Lesions due to fungal infection and, in some cases, secondary bacterial infections, were restricted to the skin. However, we were unable to obtain sufficient amounts of RNA from these sites. We therefore examined lungs for response at an epithelial surface not linked to the primary site of infection. We found that bats responded to infection with a significant increase in lungs of transcripts for Cathelicidin (an anti-microbial peptide) as well as the immune modulators tumor necrosis factor alpha and interleukins 10 and 23. In conclusion, hibernating bats can respond to experimental P. destructans infection by activating expression of innate immune response genes.