Predation on leeches in a weedy pond

Abstract

SUMMARY. 1. A range of sizes of Erpobdelta octoculata fL.), Glossiphonia complanata(L.) and Helobdella stagnalis(L.) were introduced to a small weeded pond harbouring invertebrate and amphibian predators. Control leeches were kept in protective cages. Subsequently, gut contents of potential predators were tested against three anti‐leech sera, using the precipitin test. Five of fifteen species tested had fed on leeches; Agabus, Pyrrhosoma, Aeshna, Sympetrum and larval Trilurus.2. The size distributions of introduced and surviving leeches were compared. Predation pressure had been greatest on smaller leeches and this may have accounted for the observed differential mortality between leech species.3. It is concluded that predation may cause significant mortality in leech populations in weeded ponds, with severity determined by the types and abundance of predators present.