Differences in reproductive characteristics among field populations of Polycelis tenuis (Platyhelminthes) in a metal contaminated stream by M.B.M.

Abstract

Rhiophilous planarians (Platyhelminthes, Tricladida, Paludicola) are scavengers and/or predators inhabiting the interface layer between water and sediment (Reynoldson and Davies 1970). As a result, they may be hypothesized as being highly vulnerable to pollutants (Simkiss 1990). However, field studies assessing species diversity and density for a series of taxa suggest triclads to be relatively tolerant (Gower et al. 1994; Hurd et al. 1996). This study aims to give insight in whether and how triclads react on the population level towards metal pollution in the field. Five populations of the planarian Polycelis tenuis (Ijima) were sampled up- and downstream of an ancient lead/zinc mine. In addition to the internal zinc concentrations measured for these field populations, their reproductive characteristics were estimated when culturing them under semi-natural conditions in the laboratory. The reproduction pattern was investigated in two seasons and explained in light of the internal zinc concentration in the study species and its lifecycle.