PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 117(1):95-105. 2004. A new genus of the Clausidiidae (Copepoda: Poecilostomatoida) associated with a polychaete from Korea, with discussion of the taxonomic status of Hersiliodes Canu, 1888 Ju-shey Ho and Il-Hoi Kim (JSH) Department of Biological Sciences, California State University, Long Beach, California 90840-3702, U.S.A., e-mail:
[email protected]; (IHK) Department of Biology, Kangreung National University, Kangreung, Kangwondo, 210-702, Korea, e-mail:
[email protected] Abstract. — A new genus and new species of the Clausidiidae (Copepoda: Poecilostomatoida), Hemadona clavicrura, is described based on the specimens obtained from the washings of the polychaete, Dasybranchus caudatus Grube, collected from Namhae-do Island in Korea. The new genus is characteristic in having ( 1 ) the 3rd segment of the antenna drawn out to form a sharp claw, (2) a 3-segmented maxilliped in female, and (3) an armature formula of II-4 on the third endopodal segment of leg 1 . Phylogenetic analysis on the genera of the Clausidiidae shows that Hersiliodes can not be relegated to a synonym of Hemicyclops as proposed in the recent past. It is a sister-taxon with the new genus, Hemadoma, and separated from Hemicyclops in having a 6-segmented antennule, an armature formula of 11,4 on the distal segment of the endopod of leg 1, and a medial protrusion on the proximal segment of the male max-illiped. Interestingly, the phylogenetic analysis shows also that the three genera (Conchyliurus, Leptinogaster, and Pholadicola) living in bivalve mollusks are monophyletic. Poecilostome copepods of the family Clausidiidae are known to live largely in symbiosis with various marine inverte-brates, such as alcyonarians, polychaetes, mollusks, and callianassid crustaceans. Cur-rently, the family comprises nearly 80 spe-cies in 9 genera. One of its genera, Hersi-liodes Canu, 1888, living in association with polychaetes and bivalves, has been considered almost impossible to separate from Hemicyclops Boeck, 1 872 by Bocquet et al. (1963) and Vervoort & Ramirez (1966). Furthermore, Gooding (1963) as well as Humes & Huys (1992) had even advocated the doubtfulness of keeping the genus Hersiliodes as a valid taxon in the Clausidiidae. Nevertheless, in his book on the copepods associated with the marine in-vertebrates of the British Isles, Gotto (1993) treated Hersiliodes as a valid genus of the Clausidiidae and, furthermore, in their re-port on a new species of Hersiliodes from Korea, Kim & Stock (1996) alleged that the genus differs from Hemicyclops in bearing a 6-segmented (instead of 7-segmented) an-tennule and an armature formula of 11,4 (in-stead of 1,5) on the third endopodal segment of leg 1 . However, it should be pointed out that the former character state is also found in one (out of 38) species of Hemicyclops and the latter, in all nine species of Con-chyliurus. Recently, one of us (IHK) discovered, during his general survey of the symbiotic copepods on Namhae-do Island in Korea Strait, a new genus and species of clausidiid associated with a polychaete. The new form carries, interestingly, some characteristic features of both Conchyliurus and Hersili-odes. Thus, in this paper, in addition to de-
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