Bacterial feeding by the freshwater bryozoan Plumatella fungosa (Pallas, 1768).

The present study demonstrates for the first time the capacity of a bryozoan to feed on bacteria. Qualitative feeding tests were performed in laboratory conditions with Plumatella fungosa raised from statoblasts and fed with formazan-coloured Escherichia coli. They establish that bacteria were not only ingested but digested as shown by their transit in the digestive tract and the presence of broken bacteria in the faecal pellets. The ingestion rate of E. coli was determined by measuring bacterial removal in a vessel containing a colony of P. fungosa collected from a pond. It attained 10³ cells per zooid during the first hour of the experiment, for an initial bacterial concentration of 5.5 × 10⁴ cells ml⁻¹. The filtration rate was estimated at 0.0246 ml zooid⁻¹ h⁻¹ . These results indicate the ecological role of bryozoans in water purification.