It’s a female’s world: sex ratio of polar pelagic ostracods tested across multiple spatiotemporal scales

Abstract Biased sex ratios are commonly found in nature and were also observed in this study on pelagic ostracods in both the Arctic and Southern Oceans. Because changes in sex ratio may occur in response to environmental perturbations, studying this aspect in polar regions as they continue to warm is of ecological importance. Here, a robust spatiotemporal dataset of historical and contemporary sex data was compiled to explore variation in ostracod sex ratio with respect to species, depth, region, season and ontogeny. Global ostracod populations in both the Arctic and Antarctic demonstrated a stable female bias of ~ 60–70% over all tested factors. This female bias was even higher when only the premature A-1 stage was considered, regardless of the factor. The widespread stability in stage-specific sex ratio and its subtle changes, especially in the interannual context, show that marine Ostracoda has the potential to be a model organism for more comprehensive sex ratio research, but deeper investigation into their ecology and reproduction is necessary.