Functional response analysis of size-selective predation by the notonectid predator Anisops deanei (Brooks) on Daphnia thomsoni (Sars)

Abstract

The functional response of A. deanei to uncrested D. thomsoni was calculated by predation experiments in the laboratory. A. deanei produced typical type 11 functional response curves when presented with increasing densities of any given size-class of D. thomsoni Predation rates were highest for small size-classes and decreased for prey sizes above 2 mm In mixed-prey populations A deanet showed a greater preference towards the smaller, preferred prey than was predicted from the angle-prey-type expenments, thus demonstrating an exercise of choice by the predator. Crests developed by the smaller, preferred size-classes of D. thomsoni did not act as effective anti-predator mechanisms against A. deanei which may be able to remam an effective predator on crested populations of D. thomsonl.