Three New Cryptic Species of the Freshwater Shrimp Genus Caridina (Decapoda: Caridea: Atyidae) from Hong Kong, with Notes on the C. serrata Species Group.

Three new species of freshwater atyid shrimp, namely Caridina chui sp. nov., C. bauhinia sp. nov. and C. argilla sp. nov., are described from Hong Kong, southern China using an integrative taxonomic approach. All three species belong to the C. serrata species group and differ from the other members in characteristics of the rostrum, pereiopods, and male first and second pleopods. Phylogenetic analyses based on mitochondrial COI and 16S rRNA sequences show that the C. serrata species group is polyphyletic and comprises at least four lineages. The validity of the C. serrata species group is discussed and more detailed diagnosis of the species group is proposed. The C. serrata species group sensu stricto is restricted to the nominal lineage containing C. serrata and closely related species, distinguished from other species of the C. serrata species group mainly by having relatively stout carpus of first pereiopod, stout appendix masculina of male second pleopod, and large number of spiniform setae on the uropodal diaeresis.