[Hysterothylacium petteri sp. n. (Nematoda: Ascaridata) from the Pacific Ocean swordfish]

Hysterothylacium petteri sp. n. was recovered from the stomach of Xiphias gladius occurring in the Kuroshio. The morphological difference of H. petteri from all other species of this genus is the extremely long ventricular caecum (two times more than pharynx). The species is very similar to H. corrugatum Deardorff et Overstreet, 1980 from swordfish off the American shores and corresponds to the description of Hysterothylacium sp. by Petter, Maillard, 1987. The third stage larvae of H. petteri sp. n. are probably those larval forms which were described as Contracaecum sp. l. Type IIA in Brunsdon in Boyle, 1966; Contracaecum sp. Otsuru et al.--type-B (Kikuchi et al.--type-A) in Kagei et al., 1970; Thynnascaris from Todarodes pacificus in Oshima, 1972; Contracaecum--type larva (B) in Shiraki, 1974; Hysterothylacium L3 in Weerasooriya et al., 1986; Porrocaecum sp. l. in Gaevskaya, Nigmatullin, Schuchhalter. New morphometric data on these larvae are given.