Biology subjects

Adams, D. M.

Publications and source records attributed to Adams, D. M..

7 recordsLinked to original sources

bioRxiv2026

Efficacy of intensive seawater irrigation in mitigating climate-driven increases in incubation temperature of green sea turtle (Chelonia mydas) nests.

Sea turtles exhibit environmental sex determination and face risks of over-feminization, heat-induced embryonic failure, and hatchling mortality due to rising global temperatures. Mitigating these impacts of climate change may necessitate interventions to reduce sand temperature. One proposed strategy is to irrigate nests with seawater, but uncertainties exist regarding turtle egg tolerance to saline nest sand. To test the hypothesis that sea turtle embryos can tolerate a regimen of irrigation with seawater at a management-relevant scale, we investigated the impact of two levels of large-scale irrigation using cooled seawater on green turtle nests and embryos, assessing the effects on important nest environmental factors and developmental success. Irrigation which simulated 200 mm of rain reduced the temperature in clutches by up to 5.6 {degrees}C (1.34 {+/-} 0.10 mean {+/-} SD) without adversely affecting clutch oxygen levels, sand water potential, or sand moisture content, but our irrigation regimens resulted in very low hatching success (1.5%). However, late-stage embryonic mortality predominated, suggesting that early embryos may have an unexpected tolerance to saline sand and increasing our understanding of sea turtle resilience to seawater irrigation. The observation that younger embryos may be less susceptible to seawater-associated mortality than mature embryos near hatching further informs the limitations and potential applications of seawater irrigation as a management strategy.

zoology↗

bioRxiv2026

Interacting effects of sex and age on immune responses in a polygynous bat with male-biased mortality

O_LIBats 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. C_LIO_LIWe 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. C_LIO_LIWe 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. C_LIO_LIWe 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. C_LIO_LIOur 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. C_LI

evolutionary biology↗

bioRxiv2024

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

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.

neuroscience↗

bioRxiv2021

Epigenetic predictors of maximum lifespan and other life history traits in mammals

Maximum lifespan of a species is the oldest that individuals can survive, reflecting the genetic limit of longevity in an ideal environment. Here we report methylation-based models that accurately predict maximum lifespan (r=0.89), gestational time (r=0.96), and age at sexual maturity (r=0.87), using cytosine methylation patterns collected from over 12,000 samples derived from 192 mammalian species. Our epigenetic maximum lifespan predictor corroborated the extended lifespan in growth hormone receptor knockout mice and rapamycin treated mice. Across dog breeds, epigenetic maximum lifespan correlates positively with breed lifespan but negatively with breed size. Lifespan-related cytosines are located in transcriptional regulatory regions, such as bivalent chromatin promoters and polycomb-repressed regions, which were hypomethylated in long-lived species. The epigenetic estimators of maximum lifespan and other life history traits will be useful for characterizing understudied species and for identifying interventions that extend lifespan.

evolutionary biology↗

bioRxiv2021

Universal DNA methylation age across mammalian tissues

Aging is often perceived as a degenerative process resulting from random accrual of cellular damage over time. Despite this, age can be accurately estimated by epigenetic clocks based on DNA methylation profiles from almost any tissue of the body. Since such pan-tissue epigenetic clocks have been successfully developed for several different species, we hypothesized that one can build pan-mammalian clocks that measure age in all mammalian species. To address this, we generated data using 11,754 methylation arrays, each profiling up to 36 thousand cytosines in highly-conserved stretches of DNA, from 59 tissue-types derived from 185 mammalian species. From these methylation profiles, we constructed three age predictors, each with a single mathematical formula, termed universal pan-mammalian clocks that are accurate in estimating the age (r>0.96) of any mammalian tissue. Deviations between epigenetic age and chronological age relate to mortality risk in humans, mutations that affect the somatotropic axis in mice, and caloric restriction. We characterized specific cytosines, whose methylation levels change with age across most mammalian species. These cytosines are greatly enriched in polycomb repressive complex 2-binding sites, are located in regions that gradually lose chromatin accessibility with age and are proximal to genes that play a role in mammalian development, cancer, human obesity, and human longevity. Collectively, these results support the notion that aging is indeed evolutionarily conserved and coupled to developmental processes across all mammalian species - a notion that was long-debated without the benefit of this new compelling evidence. SUMMARYThis study identifies and characterizes evolutionarily conserved cytosines implicated in the aging process across mammals and establishes pan mammalian epigenetic clocks.

developmental biology↗

bioRxiv2020

Genome Methylation Predicts Age and Longevity of Bats

Exceptionally long-lived species, including many bats, rarely show overt signs of aging, making it difficult to determine why species differ in lifespan. Here, we use DNA methylation (DNAm) profiles from 712 known-age bats, representing 26 species, to identify epigenetic changes associated with age and longevity. We demonstrate that DNAm accurately predicts chronological age. Across species, longevity is negatively associated with the rate of DNAm change at age-associated sites. Furthermore, analysis of several bat genomes reveals that hypermethylated age- and longevity-associated sites are disproportionately located in promoter regions of key transcription factors (TF) and enriched for histone and chromatin features associated with transcriptional regulation. Predicted TF binding site motifs and enrichment analyses indicate that age-related methylation change is influenced by developmental processes, while longevity-related DNAm change is associated with innate immunity or tumorigenesis genes, suggesting that bat longevity results from augmented immune response and cancer suppression.

genomics↗

bioRxiv2020

Investigating the effect of glycaemic traits on the risk of psychiatric illness using Mendelian randomisation

Data from observational studies have suggested an involvement of abnormal glycaemic regulation in the pathophysiology of psychiatric illness. This may be an attractive target for clinical intervention as glycaemia can be modulated by both lifestyle factors and pharmacological agents. However, observational studies are inherently confounded, and therefore causal relationships cannot be reliably established. We employed genetic variants rigorously associated with three glycaemic traits (fasting glucose, fasting insulin, and glycated haemoglobin) as instrumental variables in a two-sample Mendelian randomisation analysis to investigate the causal effect of these measures on the risk for eight psychiatric disorders. A significant protective effect of a unit increase in fasting insulin levels was observed for anorexia nervosa after the application of multiple testing correction (OR = 0.48 [95% CI: 0.33-0.71] - inverse-variance weighted estimate. The relationship between fasting insulin and anorexia nervosa was supported by a suite of sensitivity analyses, with no statistical evidence of instrument heterogeneity or horizontal pleiotropy. Further investigation is required to explore the relationship between insulin levels and anorexia.

genetics↗