ICHTHYOXENUS FUSHANENSIS, NEW SPECIES (ISOPODA: CYMOTHOIDAE), PARASITE OF THE FRESH-WATER FISH VARICORHINUS BARBATULUS FROM NORTHERN TAIWAN

Ichthyoxenus fushanensis, new species, a flesh-burrowing parasite of Varicorhinus barbatulus, collected from a mountain stream in northern Taiwan, is described. It resembles the only congeneric species, I. formosanus, recorded in Taiwan, but can be distinguished from the latter by the narrower forehead, smooth posterior margin of pereionites, narrower pleotelson, shorter antennae I and 2, and short carpus of pereiopod 1. The two species also differ in the structure of the mouthparts, especially the number of terminal spines on the mandible and maxilliped. In addition, the two species occur in different habitats and on different hosts. Ichthyoxenus formosanus is found in the body cavity of the fresh-water carp, Carassius auratus, occurring in lakes or ponds. The morphological differences between free-living mancas and parasitic adults of Ichthyoxenus fushanensisare compared.