Integrative Taxonomy Reveals Freshwater Shrimp Diversity (Decapoda: Atyidae: Neocaridina) ) from Kyushu and Southern Honshu of Japan, with a Discussion on Introduced Species

Correct identification of species is crucial for invasion ecology and management, particularly in aquatic systems. In this study, specimens of the freshwater shrimp genus Neocaridina from Kyushu and southern Honshu of Japan were identified by using an integrative approach that combined DNA barcoding of mitochondrial cytochrome oxidase subunit I (COI) and morphological examination. Among the eight species detected, two are native, viz. N. denticulata and N. ikiensis. Four are regarded as non-indigenous, viz. N. davidi, N. koreana, N. palmata, N. aff. palmata, which are believed to have been introduced from other East Asian countries either by the aquarium trade or as live fish bait. The remaining two species are likely cryptic native species, which have either been mistaken for known species, e.g., N. aff. denticulata, or species that have not been discovered before, e.g., N. aff. fukiensis. While the four alien species have spread widely in central Honshu, northern Kyushu and Tsushima Island, their impacts on the native species and the overall ecology remain mostly unexplored. Problems associated with using DNA barcoding for species identification are highlighted for further research.