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

Abstract

1. 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.

Prey selection of a shell‐invading leech as predicted by optimal foraging theory with consumption success incorporated into estimation of prey profitability

“…Although the foraging ecology and prey utilization of rhynchobdellid and arhynchobdellid predatory leeches have been tested previously (e.g. Davies, Wrona & Linton 1982; Brönmark & Malmqvist 1986; Wrona & Calow 1988; Blinn & Davies 1989; Davies & Kasserra 1989; Brönmark 1992; Martin, Seaby & Young 1994; Simon & Barnes 1996; Kreuter et al. 2008), prey selection of leeches was examined in only a few studies (Brönmark & Malmqvist 1986; Blinn & Davies 1989; Kreuter et al.…”

“…It is highly probable that this is only achieved after encounters with the prey. It is, however, also likely that W. laevis can detect and distinguish prey, at least the prey species, by chemosensory ability as is the case for some other predatory leeches (Sawyer 1986; Simon & Barnes 1996; Kreuter et al. 2008).…”

“…Although the foraging ecology and prey utilization of rhynchobdellid and arhynchobdellid predatory leeches have been tested previously (e.g. Davies, Wrona & Linton 1982;Bro¨nmark & Malmqvist 1986;Wrona & Calow 1988;Blinn & Davies 1989;Davies & Kasserra 1989;Bro¨nmark 1992;Martin, Seaby & Young 1994;Simon & Barnes 1996;Kreuter et al 2008), prey selection of leeches was examined in only a few studies (Bro¨nmark & Malmqvist 1986;Blinn & Davies 1989;Kreuter et al 2008) and none of these investigated the reason that led to prey selection in leeches. Unlike the sit-and-wait rhynchobdellid leech G. complanata that consumes prey with lower anti-predator defenses (Bro¨nmark & Malmqvist 1986;Bro¨nmark 1992), or the erpobdelliform predatory leech Nephelopsis obscura that consumes prey with lower mobility or vulnerability (Anholt 1986;Brown & Strouse 1988), W. laevis should be able to actively select the prey with higher profitability by choosing optimal sizes of snails and non-operculated species according to our results.…”

“…It is highly probable that this is only achieved after encounters with the prey. It is, however, also likely that W. laevis can detect and distinguish prey, at least the prey species, by chemosensory ability as is the case for some other predatory leeches (Sawyer 1986;Simon & Barnes 1996;Kreuter et al 2008). If the absence of the operculum is a character used by W. laevis to recognize and associate with prey of higher value, it may have evolved to specifically detect, identify and follow non-operculated snails.…”