Two new species in Leptocheliidae (Crustacea: Peracarida: Tanaidacea) from Japan, with notes on their phylogenetic position and aspects of morphology

Abstract

We describe two new species of leptocheliid tanaidaceans, Chondrochelia sublitoralis sp. nov. and Neoleptochelia japonica sp. nov., from Japan. Chondrochelia individuals were collected from 113 to 185 m depth in the Kumano Sea. Chondrochelia sublitoralis sp. nov. resembles Chondrochelia africana, Chondrochelia corsica, Chondrochelia taitungensis, and Chondrochelia tanykeraia in having females with slender chelipeds but differs from them in the length ratio of antennular articles and the setal pattern on maxillipeds, cheliped, pereopods 4–6, and pleopods. Males differ from Chondrochelia durbanensis, for which information on females is lacking, in having pereopod-1 propodus lacking ventrodistal spiniform setae and a uniarticulate uropodal exopod. Chondrochelia sublitoralis sp. nov. varies intraspecifically in the number of female antennular articles, five in larger and four in smaller females. Neoleptochelia japonica sp. nov., collected from the coast of Okinawa Island, differ from Neoleptochelia javaensis (previously the sole species in Neoleptochelia) in the setal pattern on antennae, maxillipeds, cheliped, and pleopods in females; and that on the cheliped in males. Male pereopods 1–3 show a unique subchelate condition that we speculate may function for clasping during copulation. Several females in both species had the second thoracomere demarcated on the carapace, whereas others did not. Cytochrome c oxidase subunit I (COI) gene sequences determined for C. sublitoralis sp. nov. and N. japonica sp. nov. showed intraspecific K2P distances of 0–0.4% and 0–0.5%, respectively. We inferred the phylogenetic positions of the two species in Leptocheliidae based on COI data.