Male-biased immune ageing in a polygynous bat

bioRxiv (Cold Spring Harbor Laboratory) · 2026-02-27

Abstract Bats have attracted considerable interest for their extraordinary longevity and ability to withstand infection by a range of pathogens without major harm. Yet, little is known about the relationship between these two characteristics, or the extent to which they vary between individuals of the same species. We investigated sources of immune variation in wild greater spear-nosed bats, Phyllostomus hastatus , via transcriptome sequencing of blood samples before and after ex vivo exposure to lipopolysaccharide, a membrane component of gram-negative bacteria. This species exhibits an extreme harem-polygynous mating system and strongly male-biased mortality, offering the valuable opportunity to explore sources of individual variation in immunity and its relation to ageing. We assessed immune variation across both sexes, males of contrasting social status, and the full range of ages in each sex. We observe striking immune variation associated with sex and age, with males and older bats mounting stronger inflammatory responses. These two factors interacted significantly, revealing male-biased slopes of age-related variation in immunity, the magnitude of which is consistent with male-biased ageing, supporting the predicted association between immunity and ageing. We did not observe substantial differences in immune responses between males of harem-controlling or subordinate bachelor status. This contrasts with prior research, particularly in primates, potentially raising questions about the taxonomic generality of socially mediated immune differences, which have attracted much attention. Our findings support recent calls for a nuanced approach to understanding immune adaptations and extended longevity in bats, informed by individual and species-level differences in ecology, resource allocation, and selection. These widely overlooked factors offer valuable insights into sources of immune variation and connections to other traits, such as differences in mortality and age-related deterioration.

Sex Differences in Telomere Length in a Bat With Female‐Biased Longevity

Ecology and Evolution · 2025-05-01 · 2 citations

ABSTRACT Telomeres, protective caps at the ends of linear chromosomes, are frequently found to shorten with age. Telomere length is commonly measured in wild populations to investigate age‐related changes in somatic integrity and is considered a hallmark of ageing. Despite interest, there is no clear picture regarding sex differences in telomere length or rate of attrition across species. Bats are of considerable interest in studies of ageing and telomeres, owing to their remarkable longevity and the absence of age‐associated telomere attrition observed in some species. Additionally, multiple bat species show evidence of sex differences in longevity. However, few studies of bat telomeres have included both sexes. We collected DNA from wild‐caught males and females of the highly polygynous greater spear‐nosed bat, Phyllostomus hastatus , in which mortality is strongly male‐biased, and measured relative telomere lengths. We found that, while telomeres were shorter in older bats, there was no evidence of shorter telomeres in males. In fact, males tended to have longer telomeres. This runs counter to our prediction of shorter telomeres in the shorter‐lived sex but is not completely unexpected in light of other observations, including that of shorter telomeres in longer lived species.

<scp>DNA</scp> Methylation Dynamics Reflect Sex and Status Differences in Mortality Rates in a Polygynous Bat

Molecular Ecology · 2025-03-21 · 5 citations

Males of polygynous mammals often do not live as long as females and, in some cases, exhibit evidence of earlier senescence. Patterns of DNA methylation (DNAm) have recently been used to predict chronological age in mammals. Whether DNAm also changes as a consequence of survival and senescence is largely untested in wild animals. In this study, we estimate mortality rates using recaptures of 2700 greater spear-nosed bats, Phyllostomus hastatus, over 34 years and DNAm profiled for over 300 adult bats. In this species, one male typically controls mating access to a group of unrelated females. Bayesian analysis reveals that mortality risk in males is 1.8 times that of females, and comparison of age-associated differences in DNAm indicates that DNAm changes 1.4 times faster in males than females. Therefore, even though the age of either sex is predicted by a common set of sites, the methylome of males is more dynamic than that of females. Sites associated with sex differences in the rate of DNAm change are sensitive to androgens and enriched on the X chromosome. Sites that exhibit hypermethylation are enriched in promoters of genes involved in the regulation of metabolic processes. Unexpectedly, subordinate males have higher mortality rates than reproductively dominant males and exhibit faster DNAm change than dominants at dozens of sites. Our results reveal that differences in mortality associated with sex and social status are reflected by changes in DNA methylation, providing novel insights into mechanisms of aging and mortality in this and likely other wild animal populations.

Utilising genomic association data for causal inference in anorexia nervosa

Mammalian Genome · 2025-07-10

Anorexia nervosa (AN) is a prevalent psychiatric disorder with high rates of mortality and limited treatment options. AN is a complex disorder, for which common variation contributes to disorder risk. To dissect the genetic architecture of AN, a variety of statistical methods can be applied. Many of these utilise genome-wide association study (GWAS) datasets to investigate biological mechanisms within disease progression in addition to broader associations between complex traits. GWAS for AN have revealed important biological insights, however, these have not translated into new pharmacotherapies. Here, we review the application of statistical methods that use GWAS, to investigate the relationship between genetic variation, biochemical compounds and complex traits to identify potential relationships which could advance our understanding of disease biology. We discuss genetic variant association data for AN, the application of gene-based and complex trait level correlation methods and approaches for establishing evidence of causality between complex traits and AN. These methods all contribute to the growing literature regarding the genetic influences of AN risk and demonstrate that statistical analysis utilising genetic data is a valuable tool to progress our understanding of this disease.

Age and Sex-Specific Hormonal Consequences of Extreme Polygyny in a Neotropical Bat

SSRN Electronic Journal · 2024-01-01

Sex, season, age and status influence urinary steroid hormone profiles in an extremely polygynous neotropical bat

Hormones and Behavior · 2024-07-26 · 4 citations

Resistance to age-related hearing loss in the echolocating big brown bat ( <i>Eptesicus fuscus</i> )

bioRxiv (Cold Spring Harbor Laboratory) · 2024-07-18 · 3 citations

Abstract Hearing mediates many behaviors critical for survival in echolocating bats, including foraging and navigation. Most mammals are susceptible to progressive age-related hearing loss; however, the evolution of biosonar, which requires the ability to hear low-intensity echoes from outgoing sonar signals, may have selected against the development of hearing deficits in echolocating bats. Although many echolocating bats exhibit exceptional longevity and rely on acoustic behaviors for survival to old age, relatively little is known about the aging bat auditory system. In this study, we used DNA methylation to estimate the ages of wild-caught big brown bats ( Eptesicus fuscus ) and measured hearing sensitivity in young and aging bats using auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). We found no evidence for hearing deficits in aging bats, demonstrated by comparable thresholds and similar ABR wave and DPOAE amplitudes across age groups. We additionally found no significant histological evidence for cochlear aging, with similar hair cell counts, afferent, and efferent innervation patterns in young and aging bats. Here we demonstrate that big brown bats show minimal evidence for age-related loss of peripheral hearing sensitivity and therefore represent informative models for investigating mechanisms that may preserve hearing function over a long lifetime.

Resistance to age-related hearing loss in the echolocating big brown bat ( <i>Eptesicus fuscus</i> )

Proceedings of the Royal Society B Biological Sciences · 2024-11-01 · 3 citations

Hearing mediates many behaviours critical for survival in echolocating bats, including foraging and navigation. Although most mammals are susceptible to progressive age-related hearing loss, the evolution of biosonar, which requires the ability to hear low-intensity echoes from outgoing sonar signals, may have selected against the development of hearing deficits in bats. Many echolocating bats exhibit exceptional longevity and rely on acoustic behaviours for survival to old age; however, relatively little is known about the ageing bat auditory system. In this study, we used DNA methylation to estimate the ages of wild-caught big brown bats ( Eptesicus fuscus ) and measured hearing sensitivity in young and ageing bats using auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). We found no evidence for hearing deficits in bats up to 12.5 years of age, demonstrated by comparable thresholds and similar ABR and DPOAE amplitudes across age groups. We additionally found no significant histological evidence for cochlear ageing, with similar hair cell counts, afferent and efferent innervation patterns in young and ageing bats. Here, we demonstrate that big brown bats show minimal evidence for age-related hearing loss and therefore represent informative models for investigating mechanisms that may preserve hearing function over a long lifetime.

Unravelling the effects of ecology and history in the phenotypic convergence of fishes

2024-10-10 · 1 citations

Understanding the ecological drivers and limitations of adaptive convergence is a fundamental challenge. Here, we explore how multiple ecological factors, evolutionary history, and chance influence the phenotypic evolution of planktivorous fishes. Using ecomorphological data for over 1600 marine species, we find that planktivores are significantly more similar in phenotype than expected. However, since not all traits undergo strong selection toward a convergent ecomorph, their evolutionary trajectories have not entirely overcome ancestral differences in the multivariate trait space, resulting in conservatism. Traits important in prey detection and capture, such as eye diameter and jaw length, are strongly convergent, while general body size and shape are constrained by deep divisions between clades where historical constraints are most pronounced. We show how adaptive responses to feeding ecology intertwine with other ecological pressures and historical contingency to shape fish phenotype evolution over deep time, offering key insights into the generality of phenotype evolution.

Effects of Development on Bone Mineral Density and Mechanical Properties in the Aquatic Frog, <i>Xenopus Laevis</i>, and a Terrestrial Frog, <i>Lithobates Catesbianus</i>

Integrative and Comparative Biology · 2023-05-24 · 3 citations

The limb bones of vertebrates have a critical role in supporting the weight of the body and transmitting forces that power locomotion. The loads that limb bones experience can vary in association with a range of factors, including locomotor environment or developmental stage. Limbed vertebrates that are habitually found in environments with low locomotor loads (e.g., water) might be predicted to also exhibit limb bones with less elevated mechanical properties, such as yield stiffness and yield stress. Frogs provide a distinctive case, in which these ideas can be tested as they experience changes in both locomotor style and habitat as they develop. However, while many frog taxa shift from aquatic to terrestrial habitats as they metamorphose, some lineages, such as pipids, maintain an aquatic lifestyle even after metamorphosis, providing a comparative framework for the effects of habitat shifts on developing limbs in vertebrates. This study compares the material composition and mechanical properties of the femur between frog species that are aquatic specialists (Xenopus laevis) vs generalists that spend considerable time both on land and in water (Lithobates catesbeianus) as they transition from metamorphic tadpoles to fully grown adults. MicroCT scanning was used to determine changes in bone density related to developmental stage and hindlimb use during swimming. Microindentation was then used to collect hardness values from the cortical bone of each femur, which was used to evaluate bone material properties. We found that aquatic frogs had less overall bone mineral density (BMD) than terrestrial frogs and that BMD was more elevated in the cortical region of the diaphysis than trabeculae and distal and proximal epiphyses. Despite its less elevated BMD, bone mechanical properties were not significantly different in aquatic specialist X. laevis than in more terrestrial L. catesbeianus. Our results suggest that the limb bones of aquatic frogs may experience compensatory effects through development to offset their lower BMD. Furthermore, changes in bone density and material properties across development may help to explain some of the differences in locomotor performance found between aquatic and terrestrial metamorphic frogs, providing insight into how environmental factors might correlate with bone ossification.