The Biological Bulletin, Vol 184, Issue 1 52-56, Copyright © 1993 by Marine Biological Laboratory

ECOLOGY AND EVOLUTION

Patterns of Suspension Feeding in the Freshwater Bryozoan Plumatella repens

B. Okamura and L. A. Doolan
Department of Zoology, South Parks Road, Oxford, U. K. OX1 3PS

Feeding of large and small colonies of Plumatella repens was assessed under two flow conditions. Large colonies ingested greater numbers of particles than small colonies and feeding of colonies of both sizes increased with flow. However, the rate of increase depended on colony size. Small colonies increased feeding to a greater degree than large colonies. Mechanisms that may explain these patterns are discussed. These results contrast with an earlier study of feeding in a freshwater bryozoan. The conflicting results may reflect experimental conditions. In the previous study a small volume of still water likely entailed greater food depletion by large colonies. In our study food depletion did not occur and ambient flow carried away filtered water. We discuss how the relatively large, U-shaped lophophores of freshwater bryozoans function to produce powerful feeding currents that are suited to feeding in lotic and lentic habitats.