2019 年 24 巻 1 号 p. 49-60
We describe Parakonarus kajii sp. nov. from near Iriomote Island, Ryukyu Islands, southwestern Japan. This is the first record of Parakonarus from the North Pacific. As members in this genus show great sexual dimorphism, we checked our male and female specimens for conspecificity by using partial sequences of the cytochrome c oxidase subunit I (COI) gene. The two individuals differed by two nucleotide substitutions in 661 nt (0.3% K2P distance), indicating they are the same species. This species closely resembles P. kopure reported from New Zealand, but differs in having the ventral process on the chelipedal carpus longer than wide, the inner comb-row on the chelipedal propodus composed of 16 setae, and the dactylus and unguis of pereopods 4–6 fused in the male; and the carpi of pereopods 2 and 3 without a ventrodistal spiniform seta, the propodal palm of the cheliped with two inner simple setae at the insertion of the dactylus, and article 2 of the maxillipedal palp with one mid-outer and one outer distal simple setae in the female. On the inner surface of the chelipeds in male P. kajii, we observed an elongate plate-like structure that could be a reduced ischium.