Special Interest Group Meeting

Observations on fungi in the Zoopagaceae and Cochlonemataceae in capturing amoebae

Masatoshi Saikawa*, Toru Sakurai, Yuki Masumura and Eri Hirotani-Akabane, Department of Environmental Sciences, Tokyo Gakugei University, Japan

Species in the genus Cochlonema in the Cochlonemataceae develop a cochleate-shaped thallus in the host amoebae after conidia, short fusiform to long cylindrical in shape, are incorporated into the single-celled organisms. Each conidium germinates at its lateral wall when contact with the pellicle of amoebae. Microscopy by differential interference contrast showed that the fusiform-shaped conidium of C. cerasphorum thrust a delicate process some distance (ca. 8 mm) into the protoplasm of amoeba at ca. 7 mm per minute before germination. Amoebae could occasionally escape from the fungus infection by pulling off the basal portion of the process. Immediately after conidium germination, most of the fungal protoplasm moved through the process into a turbinate-shaped young thallus. The penetration by a delicate process could not be seen in Acaulopage ischnospora, A. lophospora, A. tetraceros, Stylopage cephalote, S. rhynchospora and Zoopage thamnospira in the Zoopagaceae. In Zoopagaceae, the penetration into amoebae is not from conidia but from persistent vegetative hyphae at the point of contact where each species captures amoebae by adhesion. In A. tetraceros, the adhesion was strong, but amoeba could escape from the fungus attack by tearing off a portion of its own body.