BackgroundThe genusHuffmanelaMoravec, 1987 (Nematoda, Trichosomoididae, Huffmanelinae), represents a group of nematodes that infect both marine and freshwater fish, and the main gross feature of infection with different species of the genus is the presence of noticeable dark spots or tracks within the parasitized tissues. The purpose of this study was to describe morphologically and morphometrically the eggs of a new marine species ofHuffmanela(Huffmanela persicasp. nov.), which was found in the form of black spots in the ovary and the tunica serosa of the stomach of the daggertooth pike conger (Muraenesox cinereus). The new species differs fromHuffmanela hamo, another species reported from musculature of this host in Japan, in egg metrics, eggshell features and targeted organ. Molecular identification and pathological examination of the lesions caused by the new species are also reported.MethodsNematode eggs with varying degrees of development were separated from the infected tissues (ovary and tunica serosa of stomach) and investigated using light and scanning electron microscopy. Different species-specific markers (small subunit ribosomal DNA, 18S; large subunit ribosomal DNA, 28S; internal transcribed spacer, ITS) were used for molecular identification and phylogenetic study of the new species. Infected tissues were fixed in buffered formalin for pathological investigations.ResultsThe fully developed eggs ofH. persicasp. nov. are distinguished from those previously described from this host on the basis of their measurements (size, 54–68 × 31–43 µm; polar plugs, 6.4–9.7 × 8.4–12 µm; shell thickness, 3.5–6.1 µm) and a delicate but ornate uterine layer (UL) covering the entire eggshell including the polar plugs. Histopathological examination revealed a fibro-granulomatous inflammation in the ovary and the serosal layer of the stomach of infected fish. Maximum-likelihood (ML) phylogenetic analysis recovered a sister relationship between the new species of marine origin andHuffmanelaspecies previously collected from freshwater hosts.ConclusionsThe present study is the first to report the molecular characterization and phylogenetic position of a teleost-associated marine species of the genusHuffmanela. A comprehensive list of nominal and innominate populations ofHuffmanelais also provided.Graphical abstract