Biology subjects

Hospodarska, M.

Publications and source records attributed to Hospodarska, M..

3 recordsLinked to original sources

bioRxiv2025

Insights from the lack of an enigmatic trait: monomorphic sperm in evergreen bagworm moths and the evolution of sperm dimorphism

Reproductive traits contain some of the most bizarre and unintuitive innovations seen across the tree of life. Chief among these is the sperm dimorphism of butterflies and moths (Lepidoptera). Males make two types of sperm: traditional fertilizing sperm (eupyrene) and a second, non-fertilizing type (apyrene) that lacks a nucleus entirely. Despite decades of study, the function and evolution of this second sperm type has remained unclear. Here we explore the sperm biology of the evergreen bagworm moth, Thyridopteryx ephemeraeformis (Lepidoptera: Tineoidea: Psychidae), and find no evidence for non-fertilizing sperm in this species. We generate genomic, transcriptomic, and proteomic resources to characterize the apparently monomorphic sperm of this species and compare it to that of other Lepidoptera. The fertilizing sperm of the evergreen bagworm shows key differences from other studied species, especially a lack of proteolytic enzymes used to break down sperm bundles in other species. Combining this and other evidence, we offer new hypotheses for the evolution and function of this enigmatic reproductive trait. Notably, early diverging moths appear to produce far less non-fertilizing sperm in general than later diverging Lepidoptera. We infer that non-fertilizing sperm are not necessary in these taxa, perhaps because less robust packaging of fertilizing sperm enables greater mobility than in later diverging moths.

evolutionary biology↗

bioRxiv2024

Polyommatine blue butterflies reveal unexpected integrity of the W sex chromosome amid extensive chromosome fragmentation

Chromosomal rearrangements are crucial in speciation, acting as barriers to gene flow. Holocentric chromosomes, such as those in Lepidoptera, can facilitate karyotype changes. Despite chromosome fusions being more common, speciation events are mostly linked to fissions. Notable karyotypic variation is observed in three clades of the subfamily Polyommatinae (Lycaenidae), with chromosome numbers ranging from n = 10 to n = 225. This study used flow cytometry and molecular cytogenetic analyses to investigate genome sizes and karyotypes in several species of the genera Polyommatus and Lysandra with derived and modal chromosome numbers. The findings show no support for polyploidy, supporting karyotypic diversification via fragmentation of chromosomes. Species with high chromosome numbers have larger genomes, which indicates a potential role of mobile elements but contradicts the hypothesis of holocentric drive. Telomeric signals were detected at the ends of fragmented chromosomes. No interstitial telomeric sequences were detected on autosomes. Interstitial telomeric signals on sex chromosomes, however, revealed multiple sex chromosome systems in Polyommatus dorylas and Polyommatus icarus, with two karyotype races differing in sex chromosome constitution in the latter. Pool-seq and coverage analyses indicated shared fusion of sex chromosomes with an autosome bearing the rDNA locus, followed by a fusion with chromosome 20 in the Czech population. Notably, the W chromosome resists fragmentation, likely due to epigenetic silencing protecting it from activity of mobile elements.

genomics↗

bioRxiv2024

Sex chromosome turnover in African annual killifishes of the genus Nothobranchius

Sex chromosomes of teleost fishes often have low levels of differentiation and undergo frequent turnovers. Annual Nothobranchius killifishes comprise representatives with male-heterogametic XY or X1X2Y sex chromosome systems, scattered across their phylogeny, nested within species lacking cytologically detectable sex chromosomes. They thus provide a suitable system to study sex chromosome evolution and turnover. Here, we combined molecular cytogenetics and genomic analyses to examine several multiple sex chromosome systems in Nothobranchius spp. and their outgroup Fundulosoma thierryi. We used fluorescence in situ hybridization with three sex chromosome-specific painting probes and bacterial artificial chromosomes (BAC) bearing eight orthologues of genes found to be repeatedly co-opted as master sex determining (MSD) genes in fishes. Our results suggest at least four independent origins of sex chromosomes in the genus Nothobranchius. The synteny block carrying amhr2 gene was shared by X1X2Y systems of N. brieni, N. guentheri and N. lourensi, but the autosomal additions and the overall neo-Y chromosome structure differed among these species. On the other hand, gdf6 gene was localized to neo-Y of F. thierryi. None of the mapped MSD gene candidates seems to determine sex in N. ditte. We further sequenced genomes of F. thierryi female and N. guentheri male by long-read platforms and performed analyses of male and female Pool-seq data and coverage to delimit their non-recombining regions, determine degree of their differentiation, and thus complement the cytogenetic data in assessing potential MSD genes. We found low level of sex chromosomes differentiation in F. thierryi. In N. guentheri, however, we identified two distinct evolutionary strata on neo-Y. The amhr2 gene resides in the younger stratum and has low allelic variation, which questions its role in sex determination.

evolutionary biology↗