Four new species of isopods (Crustacea, Isopoda) from South Korea

Four new isopods, Amakusanthura intermedia sp. nov., Apanthura laevipedata sp. nov., Idarcturus trispinosus sp. nov., and Neastacilla paralongipectus sp. nov., are reported from the sublittoral zones in Korean waters. Amakusanthura intermedia sp. nov. differs from its congeners by the following features: the uropodal exopod is sinuous distally and with pointed apex; the maxillipedal endite is present and reaching to the distal end of fused palp articles I and II; and the propodal palm of pereopod I is stepped. Apanthura laempedata sp. nov. can be distinguishable from its related species by the following characteristics: the eye is lacking; the propodal palm of pereopod I is not stepped; and the uropodal exopod is not sinuous. Idaraurus trispinosus sp. nov. is diagnosed by the following features: the cephalon has three dorsal spines and a pair of lateral spines; pereonite IV has two pairs of small dorsolateral spines, four pairs of dorsal spines, and one posterior spine; and the pleotelson has three pairs of wings laterally. Neastacilla pardongipectus sp. nov. can be distinguished by the following characteristics: the body is smooth and lacking dorsal spines or tubercles; pereonite IV is approximately 5.4x longer than pereonites II and III together; and the pleotelson has two pairs of lateral wings. In this paper, detailed descriptions and illustrations of the four species are presented. A key to the genera of the family Arcturidae and keys to the species of the four genera are also provided.