Abstract
Mycetophagous females of Iotonchium ungulatum inhabit in the knots produced on the gills of fruiting bodies of the oyster mushroom, Pleurotus ostreatus (1, 8), and are supposed to feed on hyphae forming knots. AIHARA (1) described the morphological characteristics of the nematode, but he did not describe its oesophagus in detail because of the overlapping ovary.
POINAR (4) noted that the mycetophagous females of I. californicum possess morphological features characteristic of Hexatylus species. He called this female “hexatyloid form”. In Hexatylus viviparus, the position of oesophagus and intestine had been the subject of controversy (2, 3, 6, 7), but he did not discuss the matter in “hexatyloid” females of I. californicum (4).
Some of our I. ungulatum specimens collected in Kyoto are appropriate for observing anterior alimentary tract of mycetophagous females. We describe the structure of this organ, and compare it with that of I. californicum and H. viviparus.
