Effect of food level on reproduction and metamorphosis in the suctorian protozoanTokophrya lemnarum stein.

A sessile predator, the ciliated protozoanTokophrya lemnarum, produces a motile embryo. The embryo attaches to a substrate and secretes a stalk at metamorphosis. Production of the offspring is closely synchronized with the feeding schedule, so that fecundity per individual varies directly with the food level. Some embryos produced by an adult do not attach at metamorphosis but become freely floating adults. The percentage of nonattaching embryos is compared between adults fed high or low level diets. Adults on the low level diet produce 25% or more nonattaching embryos compared to 10% or less produced by adults on a high level diet. If the adult is switched from a low level diet to a high level diet, or from high to low, the percentage of nonattaching embryos produced on each diet remains relatively constant. It is suggested that nonattachment provides one means for individuals to escape areas of low prey density and availability.