Biology subjects

Dechmann, D. K. N.

Publications and source records attributed to Dechmann, D. K. N..

9 recordsLinked to original sources

bioRxiv2026

Rapid population decline of Egyptian fruit bats on Cyprus

Preventing extirpations requires timely detection of rapid declines and immediate conservation response. Egyptian fruit bats (Rousettus aegyptiacus) are globally listed as Least Concern, but their genetically isolated population in Cyprus is Critically Endangered. We document a severe ongoing decline of the Cypriot R. aegyptiacus population observed during standardized counts at major roost sites. April 2024 counts at four principal roosts recorded 4633 bats. Surveys in December 2025 documented 554 individuals across the same sites. April 2026 counts revealed a 90.1% decline since April 2024. Additionally, we found numerous dead bats at three roosts, and residents across the island reported dead bats, suggesting an acute mortality event beginning in early 2025. The cause remains unknown. Given the magnitude and pace of decline, this population potentially faces imminent extirpation. We recommend immediate action to protect roosting and foraging habitat, along with coordinated diagnostics, expedited research permits, standardized monitoring, and technical collaboration to identify and mitigate underlying causes of high mortality.

ecology↗

bioRxiv2026

BatSpot: a retrainable neural network for automatic detection and classification of bat echolocation and detection of buzzes and social calls

O_LIBats are a diverse taxonomic group that display a wide range of interesting behaviours. Many bats are keystone species for their ecosystem, are IUCN Red-listed as vulnerable to critically endangered, and subject to human-wildlife conflicts arising from anthropogenic expansion. Yet bats remain understudied both with respect to behaviour, population ecology and conservation status. One of the major challenges when studying bats is obtaining data. Their nocturnal lifestyle and use of ultrasonic echolocation makes them difficult to track and record using traditional methods. Recent advances in passive acoustic monitoring have allowed researchers to record large amounts of data, but the detection and classification of vocalisations remain a challenge. Most available tools are either for profit or are limited to a narrow geographic range, and mostly focus on echolocation search phase calls. C_LIO_LIHere we present BatSpot, a convolutional neural network trained to detect search phase calls, buzzes and social calls. It also offers the option to classify the search phase calls to species(-complex) level. We provide a GUI that allows researchers to retrain or transfer-train the models for their specific needs and validate the performance. C_LIO_LIWe test the performance of all models and show that they perform better than both commercial and open-source solutions (search phase file level F1: 0.97 vs 0.96, buzz detector F1: 0.95 vs 0.11). We furthermore show that retraining the search phase call detector for a new country with examples from just 59 recordings massively improves the performance (F1: 0.48 to 0.79). C_LIO_LIBatSpot will enable bat researchers globally to automate detection and classification with minimal effort and includes novel options for social call and buzz detection, typically not featured in other automated tools for bat monitoring. C_LI

ecology↗

bioRxiv2025

Defying expectations: sex-biased telomere dynamics and extended lifespan in the tropical bat species, Molossus molossus.

Telomeres are key biomarkers of cellular ageing, yet their dynamics remain poorly studied in tropical and short-lived bat species. Here, we present the first investigation of telomere length across age in Molossus molossus, a tropical bat historically categorised as the shortest-lived bat on record. Through a multi-year mark-recapture study in Gamboa, Panama, we sampled 492 individuals (n = 317 females, 175 males) and documented a female M. molossus surviving to at least 13 years of age, more than doubling the previously reported maximum lifespan of 5.6 years. Across the population, relative telomere length (rTL) showed no overall significant decline with age. No evidence was found for sex-specific rates of telomere attrition. Rather these results suggest that males and females follow parallel age-related telomere trajectories, with any sex differences primarily reflecting differences in mean telomere length rather than ageing dynamics. Overall, the findings here challenge previous assumptions about the lifespan and ageing biology of M. molossus. They demonstrate that telomere maintenance is not limited to temperate bats, show that sex differences in telomere biology are subtle and species-specific, and reinforce the value of long-term field studies for understanding ageing processes in the wild.

molecular biology↗

bioRxiv2025

Gene expression reveals the pancreas of Aselli as a critical organ for plasma cell differentiation in the common shrew

Almost all mammals rely on the thymus and bone marrow to generate and differentiate B- and T cells essential for adaptive immunity. A few members of the family Soricidae, or true shrews, have also evolved the pancreas of Aselli, a kidney-sized organ hypothesized to serve this primary immune role, and whose gene expression profile is unknown. Here we introduce transcriptomes of juvenile Sorex araneus pancreas of Aselli, compare them to those of the spleen and chick bursa of Fabricius, an analogous and bird-specific organ, and explore differential expression overlaps with positively selected genes. While differential gene expression analyses revealed overexpression of genes that regulate the differentiation of B cells into long-term plasma cells (e.g., IRF4, XBP1, PRDM1) compared to the spleen and more convergent expression with the bursa of Fabricius than expected by chance (including IRF4), overlaps with positive selection were as expected and included PTPRCAP, which regulates both T and B cell antigen responses and lymph node size. Our results support the specialized role of the pancreas of Aselli in adaptive immunity, and we propose this unique organ evolved at the intersection between extreme metabolic demands and high parasite burdens in tiny yet very active shrews.

evolutionary biology↗

bioRxiv2025

Seasonal brain regeneration and chromosome instability are linked to selection on DNA repair in Sorex araneus

Sorex araneus, the Eurasian common shrew, has seasonal brain size plasticity (Dehnels phenomenon) and abundant intraspecific chromosomal rearrangements, but genomic contributions to these traits remain unknown. We couple a chromosome-scale genome assembly with seasonal brain transcriptomes to discover relationships between molecular changes and both traits. Positively selected genes enriched the Fanconi anemia DNA repair pathway, which prevents the accumulation of chromosomal aberrations, and is likely involved in chromosomal rearrangements (FANCI, FAAP100). Genes involved in neurogenesis show either signatures of positive selection (PCDHA6), seasonal differential expression in the cortex and hippocampus (Notch signaling), or both (SOX9), suggesting a role for cellular proliferation in seasonal brain shrinkage and regrowth. Both positive selection and evolutionary upregulation in the shrew hypothalamus of VEGFA and SPHK2 indicate adaptations in hypothalamic metabolic homeostasis have evolved together with Dehnels phenomenon. These findings reveal genomic changes central to the evolution of both chromosomal instability and cyclical patterns in brain gene expression that characterizes mammalian brain size plasticity. TeaserGenomic and expression variations are key to chromosomal instability and seasonal brain plasticity in the common shrew.

evolutionary biology↗

bioRxiv2024

Seasonal and comparative evidence of adaptive gene expression in mammalian brain size plasticity

Contrasting almost all other mammalian wintering strategies, Eurasian common shrews, Sorex araneus, endure winter by shrinking their brain, skull, and most organs, only to then regrow to breeding size the following spring. How such tiny mammals achieve this unique brain size plasticity while maintaining activity through the winter remains unknown. To discover potential adaptations underlying this trait, we analyzed seasonal differential expression in the shrew hypothalamus, a brain region that both regulates metabolic homeostasis and drastically changes size, and compared hypothalamus expression across species. We discovered seasonal variation in suites of genes involved in energy homeostasis and apoptosis, shrew-specific upregulation of genes involved in the development of the hypothalamic blood brain barrier and calcium signaling, as well as overlapping seasonal and comparative gene expression divergence in genes implicated in the development and progression of human neurological and metabolic disorders, including CCDC22. With high metabolic rates and facing harsh winter conditions, Sorex araneus have evolved both adaptive and plastic mechanisms to sense and regulate their energy budget. Many of these expression changes mirrored those identified in human neurological and metabolic disease, highlighting the interactions between metabolic homeostasis, brain size plasticity, and longevity.

evolutionary biology↗

bioRxiv2023

Molecular mechanisms of seasonal brain shrinkage and regrowth inSorex araneus

To meet the challenge of wintering in place many high-latitude small mammals reduce energy demands through hibernation. In contrast, short-lived Eurasian common shrews, Sorex araneus, remain active and shrink, including energy-intensive organs in winter, regrowing in spring in an evolved strategy called Dehnels phenomenon. How this size change is linked to metabolic and regulatory changes to sustain their high metabolism is unknown. We analyzed metabolic, proteomic, and gene expression profiles spanning the entirety of Dehnels seasonal cycle in wild shrews. We show regulatory changes to oxidative phosphorylation and increased fatty acid metabolism during autumn-to-winter shrinkage, as previously found in hibernating species. But in shrews we also found upregulated winter expression of genes involved in gluconeogenesis: the biosynthesis of glucose from non-carbohydrate substrates. Co-expression models revealed changes in size and metabolic gene expression interconnect via FOXO signaling, whose overexpression reduces size and extends lifespan in many model organisms. We propose that while shifts in gluconeogenesis meet the challenge posed by high metabolic rate and active winter lifestyle, FOXO signaling is central to Dehnels phenomenon, with spring downregulation limiting lifespan in these shrews.

genetics↗

bioRxiv2023

Large captivity effect based on gene expression comparisons between captive and wild shrew brains

Compared to their free-ranging counterparts, wild animals in captivity experience different conditions with lasting physiological and behavioral effects. Although shifts in gene expression are expected to occur upstream of these phenotypes, we found no previous gene expression comparisons of captive vs. free-ranging mammals. We assessed gene expression profiles of three brain regions (cortex, olfactory bulb, and hippocampus) of wild shrews (Sorex araneus) compared to shrews kept in captivity for two months and undertook sample drop-out to examine robustness given limited sample sizes. Consistent with captivity effects, we found hundreds of differentially expressed genes in all three brain regions, 104 overlapping across all three, that enriched pathways associated with neurodegenerative disease, oxidative phosphorylation, and genes encoding ribosomal proteins. In the shrew, transcriptomic changes detected under captivity resemble responses in several human pathologies, including major depressive disorder and neurodegeneration. While interpretations of individual genes are tempered by small sample sizes, we propose captivity influences brain gene expression and function and can confound analyses of natural processes in wild individuals under captive conditions.

genetics↗

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↗