Free-living nematodes of the families Selachinematidae and Richtersiidae in the White Sea (Nematoda, Chromadoria)

Abstract

Eight species of the families Selachinematidae and Richthersiidae are found in the White Sea, North Russia. The new species, Gammanema anthostoma sp. n., is distinguished by the peculiar chelostomal rugae protruding from the mouth. Its males differ from the males of all Gammanema species in the lack of supplementary organs. Females of G. anthostoma sp. n. differ from those of the two Gammanema species whose males are hitherto unknown: from the females of G. mediterraneum Vitieello, 1970 in the lacking long somatic setae, value of the b index and three times longer body; and from females of G. cancellatum Gerlach, 1955 in the lenth ratio of the outer labial and cephalic setae. Six swpecies (Choniolaimus panicus, Gammanema fennicum, G. rapax, Halichoanolaimus robustus, Latronema aberrans, Richthersia inaequalis) are recorded from the White Sea for the first time. G. fennicum is ressurected as a good species and its male is described for the first time; this species is strongly sexually dimorphic. G. rapax is a very variable species or even a group of species, as its redescriptions differ in important details: its wide distribution needs confirmation. In males of Latronema aberrans, the spermatozoa are filiform unlike rounded spermatozoa of other selachinematids.