FIVE SPECIES OF THE GENUS EURYSTOMINA FILIPJEV, 1921

Abstract

Free-living marine nematodes of the genus Eurystomina Filipjev, 1921, are relatively long and slender species, belonging to the order Enoplida. They are prominent especially in that males have characteristic two pairs of pre-cloacal supplements. But the taxonomy of them is still much in confusion because of their relatively simple body structure, which is a prevailing situation in the taxonomy of the order Enoplida. In their checklist of aquatic nematodes, Gerlach and Riemann (1973-74) enumerated 42 species which had been described as Eurystomina, but considered only half of them as valid species. Up to the present only one species of the genus Eurystomina, i.e. E. ophthalmophora, has been known from Japan and adjacent regions (Steiner, 1921; Wieser, 1955; as for the species name, see the discussion below). In the course of the author's works on Japanese marine nematode fauna, especially on the order Enoplida, additional four species which are apparently belonging to the genus Eurystomina have been found. The descriptions of them, together with E. ophthalmophora, and some discussions on the taxonomical characters of the genus are given below. Specimens were collected from shores around Shirahama, on the southern west Kii Peninsula, and from intertidal zones of Kuroshima Island and Iriomote Island, in the southest part of Ryukyu Islands.