Abstract
Mycetophagous females, males and infective females of the genus Iotonchium which had not been known in Japan were found from gill-galled oyster mushrooms, Pleurotus ostreatus, which were collected at some localities of Tottori Prefecture in the late autumn of 1992 and 1993. By comparison with seven previously described species of Iotonchium, this nematode was named I. ungulatum n. sp. (“hiratake-hidakobu-senchu” in Japanese) and described here. The new species is apparently distinguished from I. bifurcatum, I. californicum, I. cephalostricum, I. fungorum, I. imperfectum and I. macrospiculatum by having peculiar L-shaped spicules with a paw-like tip in the male (specific name is derived from this characteristic). From I. mycophilum whose male has not been known, the new species is differentiated by the shorter body length and the pointed tail terminus in the infective female.
