Zoological Studies 50(5): 588-604 (2011)

The similis-Subgroup within Triconia (Copepoda: Cyclopoida: Oncaeidae) from Korean Waters (East China Sea), Including a New Species Jin-Hee Wi1, Kyoung-Soon Shin2, and Ho-Young Soh1,* 1Division of Marine Technology, Chonnam National Univ., Yeosu 550-749, Korea 2South Sea Research Institute, KORDI, Geoje 656-830, Korea

(Accepted April 11, 2011)

Jin-Hee Wi, Kyoung-Soon Shin, and Ho-Young Soh (2011) The similis-subgroup within Triconia (Copepoda: Cyclopoida: Oncaeidae) from Korean waters (East China Sea), including a new species. Zoological Studies 50(5): 588-604. Two small oncaeid copepods were collected in June 2009 using a conical net of a fine mesh size (100 µm) from off the southern coast of Cheju I., Korea (Northwest Pacific) which is affected by the Tsushima Warm Current. One species is newly recorded from Korean waters, and the other is new to science. The new species, Triconia denticula sp. nov., differs from already described similis-subgroup species by a “bulging” lateral margin at the midlevel of the female genital double-somite covered by minute scales on the middorsal and lateral surfaces; the anal somite of the species is ornamented with small scales on the dorsal and ventral surfaces; and the exopodal outer seta of P5 is very long and plumose, which is longer than those of other species of the similis-subgroup. Males of this species were not found so far. Triconia umerus (Böttger-Schnack and Boxshall) which is newly recorded from Korean waters is redescribed with a comparison of its morphological details and differences from published studies. In addition, the zoogeography of the similis-subgroup described from the Northwest Pacific is summarized. http://zoolstud.sinica.edu.tw/Journals/50.5/588.pdf

Key words: Taxonomy, Oncaeid copepods, Triconia, Tsushima Warm Current, Zoogeography.

Of small-sized copepods, oncaeid copepods recent achievements in the taxonomic study of play important ecological roles as they have high oncaeid copepods proved that morphological numerical abundances (Kršinić 1998, Hopcroft characteristics for identifying and separating et al. 2001) and species diversity (Heron and species, such as details of the mouthparts, Bradford-Grieve 1995, Böttger-Schnack 1999 2001 morphometrics, and ornamentation of elements, 2003, Heron and Frost 2000). Due to identifi- are of sufficient quality for correct taxonomic cation difficulties caused by their small body size, identification (Böttger-Schnack 1999 2005, Böttger- insufficient taxonomic description, and close Schnack and Schnack 2009, Böttger-Schnack and morphological similarities among species of this Machida 2010). family, a number of sibling species and species Of over 100 species of oncaeid copepods groups have sometimes been designated as so far described (http://copepodes.obs-banyuls.fr/ forms without sufficient definition for subsequent en), about 30 species were recorded from several identification (Heron and Frost 2000), and this Pacific areas: the Southwest Pacific (18 species: has often led to erroneous identifications and Heron and Bradford-Grieve 1995); the Northeast underestimation of the actual species diversity of Pacific (30 species: Heron and Frost 2000); the oncaeids (Böttger-Schnack et al. 2004). However, East China Sea (10 species: Chen and Zhang

*To whom correspondence and reprint requests should be addressed. Tel: 82-61-6593191. Fax: 82-61-6593199. E-mail:[email protected]

588 Wi et al. – Two Species of The similis-Subgroup within Triconia 589

1974; 8 species: Zheng et al. 1982); Japanese profiles of temperature and salinity (T-S) were waters (13 species: Itoh 1997); and Korean waters recorded using SEB 911plus CTD at the station. (10 species: Wi et al. 2008 2009 2010). However, Specimens were fixed in 99.8% ethanol (not taxonomical criteria of many oncaeid species from denatured). Oncaeid species were sorted out from Pacific ar