Biology subjects

Hamadou, A. B.

Publications and source records attributed to Hamadou, A. B..

4 recordsLinked to original sources

bioRxiv2026

Integrated genomics and transcriptomics reveal mechanisms of extreme dietary adaptation in vampire bats

Vampire bats are the only tetrapods that feed exclusively on blood. To uncover the molecular basis of this extreme dietary specialization, we generated six new reference genomes, including genomes of all three vampire bat species, and integrated comparative analyses of gene sequence evolution (selection signatures, duplications, and losses) with transcriptomic data from six major organs to identify shifts in gene expression. Our integrative analyses reveal sequence or expression changes in 150 genes that illuminate the genetic mechanisms underlying sanguivory. Through comparative analyses and experiments, we show that the enlarged vampire bat stomach has increased connective tissue content enabling extreme expansion, is pH-neutral, and exhibits reduced mucus production, together providing molecular insights into its shift from a digestive to an absorptive organ for water, electrolytes, and vitamins. We further uncover pathway-level molecular changes underlying altered gastrointestinal motility; trypsin-dependent protein digestion; upregulated amino acid catabolism with key aspects diverging from other mammals; impaired dietary fat digestion counterbalanced by increased fatty acid synthesis; defective sugar metabolism and natural insulin deficiency; enhanced heme iron absorption; and adult splenic erythropoiesis. Together, these findings reveal the molecular adaptations that enable one of the most extreme dietary transitions among vertebrates.

evolutionary biology↗

bioRxiv2026

Closely related, yet phenotypically different - Genome assemblies of two sister species of widow spiders: Latrodectus hasselti and L. katipo, Theridiidae

Widow spiders of the genus Latrodectus are important animals for biomedical, pest and conservation research. Here, we present the assembled genomes of two closely related Latrodectus species: the Australian L. hasselti and the New Zealand endemic L. katipo. The genome of L. katipo consists of 13 scaffolds likely corresponding to chromosomes (90% of the total length) and 1267 short scaffolds (10%). It has a total length of 1.5 Gbp and BUSCO of 94.9%. The genome of L. hasselti consists of 379 scaffolds and has a total length of 1.7 Gbp and a BUSCO score of 95.4%. The repeat content is very similar in both genomes with a total proportion of 37.2% for L. katipo and 39.9% for L. hasselti. Genome annotation predicted 12706 and 15111 genes for L. katipo and L. hasselti respectively. An ortholog analysis shows large overlap between orthogroups suggesting either duplication events in L. hasselti or loss of genes in L. katipo.

genomics↗

bioRxiv2026

Ontogenetic variation in composition and bioactivity of common adder (Vipera berus) venom revealed by genome-guided proteomics and in vitro functional assays

1Ontogenetic shifts in diet are well documented in snakes and are increasingly linked to age-related venom variation. The common adder, Vipera berus, exhibits a dietary transition from predominantly ectothermic prey in its early life to increasingly incorporating endothermic prey as an adult. Here, we investigate whether this dietary shift is reflected in age-related changes in the venom composition and bioactivity of V. berus. Venoms from captive-bred V. berus from Germany were obtained and pooled across five age groups, from neonates to adults. Venom profiles were assessed by SDS-PAGE and genome-guided shotgun proteomics, with quantification based on normalized spectral abundance factors (NSAF) using a toxin-gene catalogue generated from a novel V. berus genome assembly. In parallel, we assayed general protease and PLA2 activities, as well as FXa-, thrombin-, and plasmin-like activities, and cytotoxicity toward mammalian cell lines. We identified two distinct age-related venom phenotypes (ontotypes): an svMP/CTL-rich ontotype A ([≤]1 year) and an svSP/PLA2-rich ontotype B ([≥]2 years). Functionally, protease activity decreased with age, whereas thrombin-like, plasmin-like and PLA2 activities, and cytotoxicity, increased. Our findings indicate an ontogenetic shift in composition and activities of V. berus venom that parallels dietary transitions and potentially reflect adaptation to differing prey physiologies.

biochemistry↗

bioRxiv2024

De Novo Genome assembly of the Caucasian dwarf goby Knipowitschia cf. caucasica, a new alien Gobiidae invadingthe River Rhine

The Caucasian dwarf goby Knipowitschia cf. caucasica is a new invasive alien Gobiidae spreading in the Lower Rhine since 2019. Little is known about the invasion biology of the species and further investigations to reconstruct the invasion history are lacking genomic resources. We assembled a high-quality chromosome-scale reference genome of Knipowitschia cf. caucasica by combining PacBio, Omni-C and Illumina technologies. The size of the assembled genome is 956.58 Mb with a N50 scaffold length of 43 Mb, which includes 92.3 % complete Actinopterygii Benchmarking Universal Single-Copy Orthologs. 98.96 % of the assembly sequence was assigned to 23 chromosome-level scaffolds, with a GC-content of 42.83 %. Repetitive elements account for 53.08 % of the genome. The chromosome-level genome contained 26,404 transcripts with 23,210 multi-exons, of which 26,260 genes were functionally annotated. In summary, the high-quality genome assembly provides a fundamental basis to understand the adaptive advantage of the species.

genomics↗