Incongruence between morphological and molecular diversity in Coxicerberus fukudai (Ito, 1974) (Isopoda: Microcerberidea) from East Asia

Coxicerberus fukudai (Ito, 1974) (Isopoda) is redescribed from Korean and Japanese localities. Molecular analysis based on two mitochondrial markers (mtCOI and Cytb) of the studied populations shows two diverged lineages, reflected in high (10.5% and 9.5%) pairwise differences and high haplotype diversity. One of the clades is shared by Korean and Japanese populations with little divergence rate (0.02% and 0.03%), and another is only found in Korea. We failed to find any consistent morphological differences across the examined populations, probably indicating the existence of cryptic species. We also examined the possible influence of the endosymbiotic bacterium Wolbachia on the haplotype diversity. Infection with the bacterium shows a distinct distribution pattern, with all the southern Korea populations being infected, whereas the northern populations are not.