PREDATION RISK OF TYPICAL OVOID AND WINGED MORPHS OF EUPLOTES (PROTOZOA, CILIOPHORA)

Freshwater species of the genus Euplotes (Protozoa, Ciliophora) change their morphology in the presence of some of their predators. The cili ates develop extended lateral 'wings' as well as dorsal and ventral pr ojections which make engulfment by predators more difficult. In a seri es of laboratory experiments ingestion rates of four protozoan predato rs, the ciliates Lembadion bullinum, Dileptus anser, Stylonychia mytil us and Urostyla grandis, and one metazoan predator, the turbellarian S tenostomum sphagnetorum, on three species of Euplotes (E. octocarinatu s, E. patella and E. aediculatus) were determined. It was calculated t hat the probability of rejection by a predator changed from 1:1 for ov oid morphs of Euplotes to about 2:1-20:1 for 'winged' morphs of Euplot es, dependent on the prey and predator species that were combined. The nutritional condition of the prey also had some influence. In mixed-s pecies cultures of prey and predators, transformed cells of E. octocar inatus survived for several months.