Colonization of non-living surfaces in streams by peritrich ciliates

Cleaned stones or glass slides placed in streams were quickly colonized by vorticellids and Carchesium, whose numbers increased for about 2 weeks before falling to a steady level by about 4 weeks. Platycola populations developed more slowly, but tended to become dominant after 3 or 4 weeks. The populations of peritrichs on surfaces already coated with 'periphyton' remained at low levels, even after the surface had been disturbed by removal to a new site. Stone surfaces carried higher peritrich populations than glass slides, though Platycola colonized grooves on glass slides to almost twice the density found on the smooth glass surface. Surface irregularities appear to enhance attachment. It is suggested that in general the densities of peritrich colonization are determined by available settlement sites, available food, and predation.