Mitogenomic organization and characteristics of deep-sea pelagic ostracods from both polar regions

BACKGROUND: Mitochondrial genomes are important markers that enable the study of evolutionary history, population structure, and biogeographic patterns in polar species, offering a framework to understand how polar organisms persist and adapt to extreme environments. However, they remain understudied in ostracods, an ecologically significant group of crustaceans. This study aimed to fill this gap by assembling and annotating the complete mitochondrial genomes of five pelagic ostracod species (Boroecia maxima, B. antipoda, B. borealis, Discoconchoecia elegans, and Obtusoecia obtusata) from the Arctic and Antarctic. Next-generation sequencing was applied, followed by detailed bioinformatic analyses to characterize gene content, structural features, and evolutionary patterns within these species. RESULTS: The findings revealed a consistent gene arrangement across the five species, with the typical set of 37 genes, though some tRNA secondary structures showed species-specific variations. The mitogenomes displayed a high A + T content (71.9%–75.8%), had consistent Ka/Ks ratios under 1 indicating purifying selection, and included the unique presence of an intron in the nd3 gene, a potential marker for the halocyprid family lineage. Haplotype diversity ranged from 0.791 ± 0.041 to 1.000 ± 0.034, with singleton haplotypes dominating in all species. CONCLUSIONS: These results provided new insights into the mitochondrial architecture of pelagic ostracods from polar waters. Overall, these genomic data lay the foundation for future comparative work on the population genetics and biogeography of these pelagic ostracods, particularly regarding the bipolar connectivity of this taxon.