Investigations of the aufwuchs of freshwater sponges. I. A quantitative comparison between the surfaces of Spongilla Lacustris and three aquatic macrophytes

The aufwuchs of the epithelium of the freshwater sponge Spongilla lacustris was examined and compared qualitatively and quantitatively with that on three plant substrates common to its habitat: Nymphea odorata, Nuphar advena and Utricularia spp. Estimations of the percentage surface area with attached forms and the number of attached green algal filaments yielded significantly lower values for the sponge. Two theories explaining the mechanism effecting this reduced amount of aufwuchs are discussed.