Two unrecorded marine nematode species of Paracanthonchus (Nematoda: Cyatholaimidae) from the East Sea of Korea

The genus Paracanthonchus Micoletzky, 1924 con­ tains 72 valid species (Gerlach and Riemann, 1974). The taxon is distributed worldwide and occurs in various ha­ bitats from the shallow­ and brackish­water to deep­sea environments (Miljutina and Miljutin, 2015). The genus Paracanthonchus belongs to the subfamily Paracanthon­ chinae De Coninck, 1965 of the family Cyatholaimidae Filipjev, 1918 was established by Micoletzky (1924) from the genus Cyatholaimus Bastian, 1865 on the basis of the type species, P. caecus (Bastian, 1865), collected from brackish pool near the Belgian coast. Paracanthonchus differs from other genera of the family by its body cuti­ cle with transverse rows of fine dots, buccal cavity with larger dorsal tooth, distally expanded and dentate guber­ naculums, and tubular pre­cloacal supplements (Wieser, 1954; Schmidt­Rhaesa, 2014). Until now, seven species belonging to the genus Paracanthonchus, P. hawaiiensis Allgen, 1951, P. heterocaudatus Huang and Xu, 2013, P. kamui Kito, 1981, P. macrodon (Ditlevsen, 1918), P. mamubiae Miljutina and Miljutin, 2015, P. multisupplementatus Gagarin, 2012 and P. perspicuous Kito, 1981, have been reported from the Northwest Pacific Ocean (Wieser, 1955; Kito, 1978; 1981; Gagarin, 2012; Huang and Xu, 2013; Mil­ jutina and Miljutin, 2015). Currently, 51 species of free­ living marine nematodes representing 19 genera have been described in Korean waters, but taxonomic report on the genus Paracanthonchus is entirely unknown from Korea (Rho and Min, 2011; Barnes et al., 2012; Hong and Lee, 2014). In the present study, we provide tax­ onomic descriptions of two unrecorded marine nema­ todes, P. macrodon and P. kamui, collected from rocky intertidal seagrass on the eastern coast of Korea.