Prey location and prey choice by the freshwater leech Erpobdella octoculata using foraging kairomones

Abstract

The freshwater leech, Erpobdella octoculata, is a generalist predator feeding on prey organisms such as Tubifex spp., Chironomus spp. and Asellus aquaticus. Using different experimental designs, we studied the use of foraging kairomones by the leeches for prey location.2. Leeches were attracted to living as well as to freshly killed larvae of Chironomus sp., to Tubifex sp., and to A. aquaticus offered in Petri dishes covered with gauze. The leeches also reacted to an extract of macerated Tubifex sp. presented in agar.3. Using ion exchange chromatography, the presence of histidine and glutamic acid was demonstrated in water contaminated by living larvae of Chironomus sp. and Tubifex sp. Agar blocks containing a synthetic mixture of these compounds at concentrations above 5 mg mL−1 were attractive to the leeches.4. Choice tests showed that leeches preferred chemical signals from Tubifex sp. over larvae of Chironomus sp. No difference was found between chemicals from Tubifex sp. and A. aquaticus, and A. aquaticus and larvae of Chironomus sp.5. The results demonstrate that E. octoculata uses specific foraging kairomones in searching for prey and indicate that amino acids serve as foraging kairomones.