On water agar, Pleurotus ostreatus produces tiny droplets of toxin from minute spathulate secretory cells. Nematodes touching such droplets show a sudden and dramatic response. The head region shrinks considerably; this is accompanied by displacement of the oesophagus and (or) disruption of the tissues surrounding the oesophagus. In as little as 30 s, and usually within several minutes, the nematode becomes more or less immobilized but is not killed. Stimulated by leakage products from the immobilized host, directional hyphae converge on the body orifices of the nematode. These hyphae penetrate one or more body orifices and colonize and digest the host. Pleurotus strigosus, P. subareolatus, and P. cornucopiae behave in a similar way. On potato dextrose agar, P. cystidiosus produces numerous secretory cells, but the toxin is much less potent. On water agar directional hyphae of Pleurotus ostreatus can also be attracted to minute bacterial colonies, which are invaded and apparently digested.