The Incidence and Intensity of Predation on Lake‐Dwelling Triclads in the Laboratory

This is the authors' abstract. We don't add key points for this paper.

Predation on the four common species of lake—dwelling triclads Polycelis nigra, P. tenuis, Dugesia lugurbis and Dendrocoelum lacteum was investigated by exposing them to potential predators in the laboratory and using a serological technique to test cases of suspected predation. The highest intensities of predation were found for fish Scardinius erythrophthalmus, Rutilus rutilus, Gasterosteus aculeatus and Salmo trutta together with Odonata larvae, all species characteristics of weeded habitats. The leech, Erpobdella octoculata, the caddisfly larvae Plectrocnemia geniculata Polycentropus flavomaculatus and the snail Lymnae stagnalis fed only on the three planariid species of triclad and not on Dendroceleum lacteum. Shrunken adults and young triclads of the same size were preyed upon the equal intensity. Selection for size of triclad, irrespective of species was shown to occur in several of the predators. Despite differences in adult size of three of the triclad species, the potential effect of selection for size in the field compared to specific predation was difficult to ascertain. Dugesia lugubris was the only species which practiced cannibalism and preyed on other triclad species (Polycelis sp.)