FEEDING-BEHAVIOR OF THE POECILOSTOMATOID COPEPODS ONCAEA SPP. ON CHAETOGNATHS

Feeding behaviors of the poecilostomatoid copepods Oncaea venusta, O. mediterranea and O. conifera were examined in the coastal area of Chej u Island, south of the Korean Peninsula, from April 1993 to November 1 995. Late copepodid stages (CV, adult female and male) showed a high f requency of association with larger zooplankton such as Sagitta spp, ( Chaetognatha), Oikopleura spp. (Appendicularia), and Salpa spp. (Thali acea) in a coastal upwelling zone and around the small Munsum Island. Attack behaviors on Sagitta observed under the microscope and in the f ield showed that Oncaea approached Sagitta using their swimming legs, and then crawled chiefly to the neck regions and caudal septum (around the tail) of Sagitta spp. using their second antennae. They pierced t he body of Sagitta with their sharp maxillipeds, and moved their maxil lae and mandibles repeatedly. Midgut contents of Oncaea spp. consisted mainly of unidentified fine particles, and the greater part of the gu t was empty. Their mouthpart structure is remarkably different from ot her pelagic copepods. Such differences of the mouthpart structures and the feeding habits in the genus Oncaea around Cheju Island are discus sed in terms of feeding behavior and ecology in this coastal upwelling area. (C) 1998 Elsevier Science B.V. All rights reserved.