PLATYCOPIA ORIENTALIS, NEW SPECIES (COPEPODA, PLATYCOPIOIDA), FROM THE NORTH PACIFIC, WITH DESCRIPTIONS OF COPEPODID STAGES

A hyperbenthic copepod, Platycopia orientalis, new species (Platycopio ida), collected from sandy bottom off Okinawa, southern Japan, is desc ribed together with its copepodid stages III-V. This is the first reco rd of the order Platycopioida in the Indo-Pacific region. The paired g onopores are located ventromedially on the genital somite in females a nd ventrodistally in males. The developmental patterns of the antennul es and legs 1-5 are unique compared with the common pattern in copepod s. The distal 14 segments of the antennules are constant from CIII-CVI in the female, whereas fusion of segments in the male occurs at the m olt from CV to adult. The addition of segments to the endopod and exop od of leg 1 and to the endopods of legs 2-4 is suppressed during the l ast molt. The proximal spine on the first exopod segment of legs 3, 4, and 5 appears at CIV, CV, and CVI, respectively, one molt after the s eparation of the segment which carries it.