LIGHT AND ELECTRON-MICROSCOPY OF ZOOPHAGUS-TENTACLUM, A REDISCOVERED ROTIFER-CAPTURING AQUATIC FUNGUS FROM JAPAN

Zoophagus tentaclum Karling was recovered from submerged dead leaves c ollected in a mountain stream at Mito-sawa, Hinohara-mura, Tokyo, Japa n. This is the first report of this fungus since its discovery. The tr apping organ of the fungus is a short, lateral branch distally bearing several narrow tentacle-like hyphae, each terminating in a knob. The morphology of the rotifer-capturing fungus was almost identical to tha t described by Karling. Infection is initiated when a rotifer attempts to swallow the whole trapping organ. Electron microscopy revealed tha t the apical portion of one of the tentacles was pinched by a pair of unci of the rotifer's trophi, and an adhesive exuded only from that po rtion of the tentacle found in the trophi. Then, an accessory infectiv e branch developed, not from the tentacle, but from the distal portion of the lateral branch before penetration into the rotifer. Such a bra nch, developing before penetration of the host, has not been reported for the other two species of the genus, Z. insidians and Z. pectosporu s. The fungus was also found to capture a species of testaceous rhizop od.