Huffmanela paronai sp. n. (Nematoda: Trichosomoididae), a new parasite from the skin of swordfish Xiphias gladius in the Ligurian Sea (Western Mediterranean)

A new species of trichosomoidid nematode, Huffmanela paronai sp. n., is established on the basis of its egg morphology and biological characters. The dark-shelled, embryonated eggs of this histozoic parasite occur in masses in the epidermis of the swordfish Xiphias gladius L. (Xiphiidae, Perciformes) from the Ligurian Sea in northern Italy. The eggs are concentrated in groups appearing as black spots in the skin of the fish host, being distributed mainly on the lower part of its body (lower jaw, gill covers, pectoral, anal and caudal fins, lower half of body). The parasite's eggs are characterised mainly by their shape and markedly small size (48-51 × 21-24 µm), an aspinose surface, relatively small polar plugs, and thick egg wall (3 µm). This is the first Huffmanela species reported from fish in Europe. During studies on the fishery and biology of the swordfish, Xiphias gladius L., carried out by the junior author (F. Garibaldi) since 1990 in the Ligurian Sea, Italy, unusual black spots were noticed on the skin of some fish. Closer microscopical examination showed that they were formed by masses of dark-shelled trichinelloid eggs typical of the nematode genus Huffmanela Moravec, 1987, located in the fish epidermis. The morphological structure and measure- ments of these eggs, as well as the host type and the site of infection, showed that they undoubtedly represented an undescribed species of this genus. Since all but one species of Huffmanela, comprising histozoic parasites of fishes, have been described from their eggs only, we consider it reasonable to establish this new species on the basis of its egg morphology and biological characters, despite the lack of conspecific adult nematodes. This is in accordance with the Inter- national Code of Zoological Nomenclature.