Sexual Dimorphism on the Genus Paracalanus(Copepoda: Paracalanidae) in Korean Waters

The genus Paracalanus Boeck, 1864 dominate zooplankton communities in waters off Korean peninsula. Zooplankton samples collected from four waters (Uljin, Hadong, Youngkwang, Cheju) were sorted for specimens belonging to the genus Paracalanus. Paracalanus sp. regarded to p. paMus or p. indicus were examined. Body of male has cephalosome dorsal hump (CDH). Urosomites have four segments in female and five segments in male. In male, antennule is symmetry and fused without geniculation. The male antennule carries more aesthetascs than those in female antennule. Female P1-P4 is similar to those of male in seta and spine formular. Spinules on surface of legs are different each other. The female P5 is symmetrical, and composed of 2 segment. In male, it is aymmetrical and left leg composed of 5 segments, right leg 2-segmented. Male found patch of fine spinule on terminal inner surface of outer process on fifth segment. Sexual dimorphism appear saliently in mouth appendages. Mandible lacks of gnathobase; maxillule is apparently reduced; maxilla degrades it i]l female and remains vestiges between maxillule and maxilliped; maxilliped terminal part indistinctly articulated and carrying behind three strong plumose setae. With the absence of gnathobase in male, we conclude that male Paracalanus sp. does not feed.