A reappraisal of the genera Nannopus Brady, 1880 and Ilyophilus Lilljeborg, 1902 (Copepoda, Harpacticoida, Nannopodidae) with a description of N. parvipilis sp. nov. from South Korea

Abstract

The genera Nannopus Brady, 1880 and Ilyophilus Lilljeborg, 1902 are reappraised based on the characteristic features of a new species, Nannopus parvipilis sp. nov., collected from the brackish mud flat on Jindo Island, South Korea. Nannopus species have long been known as having a two-segmented P3 endopod. However, we discovered N. parvipilis sp. nov. having a one-segmented P3 endopod in accordance with the description of the genus by Brady. It implies that Brady’s generic diagnosis was appropriate and tentatively correct, and such species having a two-segmented P3 endopod but still being placed in Nannopus should be excluded from the genus. The genus Ilyophilus Lilljeborg, 1902, which has been regarded as a junior synonym of Nannopus, is revived to accommodate these Nannopus species. Thus, Nannopus is now composed of only two species, N. palustris and N. parvipilis sp. nov. and Ilyophilus comprises eight species: I. flexibilis Lilljeborg, 1902, I. perplexus Sars, 1909b comb. nov., I. unisegmentatus (Shen & Tai, 1964) comb. nov., I. didelphis (Fiers & Kotwicki, 2013) comb. nov., I. hirsutus (Fiers & Kotwicki, 2013) comb. nov., I. procerus (Fiers & Kotwicki, 2013) comb. nov., I. scaldicola (Fiers & Kotwicki, 2013) comb. nov., and I. ganghwaensis (Vakita, Kihara & Lee, 2016). In addition, N. palustris sensu Canu, 1892, which was commonly considered as representing the criterion of N. palustris, is established as a new species, I. canui sp. nov., based on the characteristic feature of the P3. A detailed description and illustrations of N. parvipilis sp. nov. are provided.