Observations on five species of philometrid nematodes from marine fishes in Japan

Five species of philometrid nematodes (subfamily Philometrinae) are redescribed on the basis of newly collected materials from marine fishes from Japan. The species Philometra sciaenae Yamaguti, 1941, considered by Rasheed (1963) a synonym of P. lateolabracis (Yamaguti, 1935), is re-established as a valid species and the male of this nematode, collected from the ovary of the type-host, Argyrosomus argentatus, is described for the first time; the latter is characterised mainly by the length of equally long spicules (0.108–0.126 mm) and the length ratio of the gubernaculum and spicules (1:2.25). Other species redescribed on females include Philometra inimici Yamaguti, 1941 and P. sebastisci Yamaguti, 1941 from the ovary of their type-hosts, Inimicus japonicus and Sebastiscus marmoratus, respectively, and also Philometroides seriolae (Ishii, 1931) from the musculature of Seriola quinqueradiata (type-host), and Clavinema mariae (Layman, 1930) from the subcutaneous tissue of Pleuronectes schrenki and Acanthogobius flavimanus (a new host record). For the first time, cephalic ends of some of these species were studied under the scanning electron microscope (SEM) and the character of their cephalic papillae was described. The importance of a knowledge of male morphology for the taxonomy of philometrids is stressed.