Platycopia compacta n. sp., the Second Species of Platycopioida (Crustacea: Copepoda) in the Indo-Pacific Region, with Remarks on Development, Feeding, Swimming, and Zoogeography.

Platycopia compacta new species (Copepoda: Platycopioida) is described from the hyperbenthic zone in the Tokara Islands, southern Japan. This is the second species of the order in the Indo-Pacific region, and the eighth species of the genus. The present new species is distinguishable from the closely related P. inornata from the Bahamas by (1) the formation of allobasis in the antenna; (2) two unequal setae on the basal exite of the maxillule; (3) the intermaxillipedal process with only 3 pairs of prominences at tip; (4) the fusion of the coxa and basis in leg 3; and (5) the fusion of the second and third endopod segments in female legs 3-5. Copepodid stages III, V, and VI are compared with those of P. orientalis collected from Okinawa, and differ in the developmental patterns of the antennule and legs. The presence of an intermaxillipedal process and gut content analysis revealed that Platycopia is carnivorous. The armature of legs 2-5 of the hyperbenthic genus Platycopia is stouter than that of cavernicolous platycopioids, which indicates that Platycopia may penetrate into loose sediment, whereas the latter group might be more adapted to pelagic life. The horizontal distribution of the genus Platycopia apparently exhibits a full Tethyan track.