Tricladid planarians (Turbellaria: Tricladida) in the Vltava River and selected brooks in Prague with focus on alien species Dugesia tigrina
Abstract
We studied the occurrence and ecology of tricladid planarians (Turbellaria: Tricladida) in the Vltava river and in selected brooks in the territory of Prague, Czech Republic. The emphasis was given on the alien North American species - Dugesia tigrina (Girard, 1850).
The research was based on field surveys of abundance and ecological requirements of planarians. The fieldwork was realised from August to November 2009.
Nine sites in the Vltava river, and six sites in brooks (three in the Botič brook and three in the Dalejský potok brook) were sampled. Altogether four tricladid species - Dendrocoelum lacteum, Dugesia polychroa, Dugesia tigrina and Polycelis nigra were found in the Vltava River.
In case of P. nigra, the identification should be confirmed by the anatomical study of male genitalia in future to exclude possible confusion with morphologically similar species Polycelis tenuis. Dugesia polychroa was the most frequent and the most abundant species, found on all of the nine river sites.
The alien species - Dugesia tigrina - was found in six of the nine river sites and was absent from the studied brooks. It seems to prefer localities with a natural shoreline, deeper ground and rapid water flow.
In all cases was found in co-occurrence with Dugesia polychroa. In contrast to published studies from British lakes, we did not find any evidence of competitive exclusion of native triclad species by the alien D. tigrina in the Vltava river.
The tricladid fauna of the studied brook sites was rather poor in comparison with the Vltava river. Only Dendrocoelum lacteum in low abundance was found in three of the six brook sites.