A New Species of Land-locked Freshwater Shrimp of the Genus Neocaridina (Decapoda: Caridea: Atyidae) from Iki Island, Kyushu, Japan

A new species of land-locked freshwater shrimp, Neocaridina ikiensis (Decapoda: Caridea: Atyidae), is described from Iki Island, Kyushu, Japan, based on morphological and molecular evidence. This new species can be distinguished from its congeners by a suite of characters, including rostrum structure, number of post-orbital rostral teeth, male first and second pleopods and telson structure. The molecular evidence of mitochondrial cytochrome oxidase subunit I (COI) shows this species has sufficient interspecific divergence, and its high intraspecific variation suggests that it evolved on this island over a long period of time. Based on the molecular clock estimation, the speciation of N. ikiensis n. sp. is supposed to be related with the quiescent periods of volcanoes on this island. This is the second native species of Neocaridina known, after N. denticulata (De Haan, 1844), from the main islands of Japan