Epizoic Rotifers and Microcrustaceans on Bivalves of Different Size and Behavior

Abstract

Previous mesocosm experiments with the epizoon of Dreissena polymorpha revealed that the communities of Rotifera and Crustacea were much more abundant and had higher species richness than epizoon of Unio tumidus in nature. These differences could be attributed to different environmental conditions and/or different host behavior. To test this hypothesis, we compared epizoon of D.polymorpha and U.tumidus placed in identical mesocosm conditions, in which Unio could not move vertically due to the lack of sediments. Half of the mesocosms contained D. polymorpha, the other half comprised U. tumidus. Each species of mollusks was kept in the mesocosms with eutrophic and mesotrophic conditions. Finally, we established four treatments that were replicated in triplicate mesocosms. Mesocosm experiments showed that epizoon communities of U. tumidus were even more abundant than that of D. polymorpha and their species richness was similar. Therefore, we concluded that previously revealed strong differences between epizoon communities of D. polymorpha and U. tumidus were related to the different environmental conditions and bivalve behavior.