Predator and Prey Densities as Controls of the Rate of Capture by the Predator Didinium Nasutum

An experimental investigation of the roles of predator density, prey density, and their interaction in the control of the capture rate by the predator was conducted, with Didinium nasutum as the predator and Paramecium aurelia as the prey. An analysis of variance of the results revealed that both predator densityand prey density were potential controls and that the latter was stronger than the former. The interaction effect was not significant. It is postulated that these two controls are alternates, that the capture rate is set by whichever is the more restrictive, and that the prey density control is probably a fixed internal control. The character of the predator density control remains to be determined.