Two New Species of Nipponbathynella Schminke, 1973 from South Korea, with a Brief Discussion on Korean Parabathynellid Genera (Crustacea, Bathynellacea)

Parabathynellidae is a family well known for its diversity and is endemic to the interstitial hyporheic zone of South Korea. Two new parabathynellid species, Nipponbathynella yeongchunensis sp. nov. and N. gapcheonensis sp. nov., were found through groundwater sampling on riverbanks in South Korea. Nipponbathynella yeongchunensis sp. nov. can be distinguished from its congeners by the base socket of the two dorsal setae on the antennule's first segment. Nipponbathynella gapcheonensis sp. nov. can be distinguished by the protopod of thoracopod II-IV with hairs. We provide morphological descriptions and remarks about the two new species with molecular information based on 18S rRNA and partial COI gene sequences. In addition, phylogenetic analysis, including Nipponbathynella Schminke, 1973, which had not been previously molecularly evaluated, was inferred. The results of the 18S rRNA gene phylogeny suggest a close relationship between the genera Nipponbathynella and Arisubathynella, as well as Europe-North American genera. We have also included a brief discussion and an identification key for the five known parabathynellid genera found in South Korea.