First record of males of Cypridopsis vidua (Crustacea, Ostracoda) species complex for Europe

Until recently, only asexually reproducing populations were known in Cypridopsis vidua, a species complex with one of the widest geographical distributions among non-marine ostracods. The discovery of males, most likely functional, from the United States and China has called into question its obligate parthenogen status. Here we report the first report of males for Europe, found in a small artificial pond in northern Italy. It seems plausible that sexual populations are much more widespread than hitherto known, as the recognition of males requires the dissection of individuals. Compared with the available descriptions of males belonging to Cypridopsis vidua and related species, that of the male illustrated here show morphological differences in the antennulae and prehensile palps, which in the Cypridoidea are sexually dimorphic and often diagnostic to distinguish between related species. Adult males show significantly smaller valve sizes than adult females, while adult females in which sperm were found inside the carapace have more variable lengths than those without sperm. No differences in valve coloration or dark banding pattern were found between males and females, and differences in valve outline were mostly negligible. The limitations of an exclusively morphological approach in the case of similar morphospecies are highlighted, as well as the importance of adopting objective criteria to measure the limits of morphological variability allowing the identification of separate taxonomic entities.