COPEPODID STAGES OF HEMICYCLOPS-JAPONICUS ITOH AND NISHIDA (POECILOSTOMATOIDA, CLAUSIDIIDAE) REARED IN THE LABORATORY

The complete set of copepodid stages of Hemicyclops japonicus Itoh and Nishida, 1993 (Poecilostomatoida: Clausidiidae), from Tokyo Bay, are described on the basis of specimens cultured in the laboratory from Saphirella-like copepodids. Many remarkable developmental changes, such as decrease in body length, reduction of the maxillipeds, and transformation of the labrum and the cephalosome occurred between Copepodids I and II. Sexual dimorphism first occurred in the maxilliped of Copepodid V. A comparison of morphological and ecological changes between Copepodids I and II supports the previous suggestion that Copepodid I of Hemicyclops spp. is primarily planktonic, while the later stages are more or less associated with the bottom or the host. The hypotheses on the status of Saphirella are reviewed and discussed.