The Food of Four Species of Lake-Dwelling Triclads

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Abstract
The food of Polycelis nigra, P. tenuis, Dugesia lugubris and Dendrocoelum lacteum has been examined in field specimens and by experiments. Except for D. lacteum agreement was shown by the two approaches. None of the species seem to feed upon small, intact organisms to any extent. The planariid species feed more readily on damaged prey while D. lacteum captures active prey and will also feed on damaged organisms. While there is wide overlap in the range of organisms eaten the triclad genera show distinctive preferences. Polycelis sp. are primarily oligochaete feeders, will also take arthropods but not molluscs. Dugesia is similar but also feeds readily on gastropods. Field data sugges Dendrocoelum feeds mostly on oligochaetes, laboratory evidence that it prefers arthropods, especially Asellus. There is overlap in range and size of prey between young an3 adult due in part to communal feeding. None of the triclad species are cannibalistic or prey on each other.