Growth and feeding of Fredericella sultana (bryozoa) in the outlet of a humic acid lake

Monthly observations on the bryozoa Fredericella sultana have been carried out in the outlet of a humic acid lake for more than two years. The growth of the colonies were rapid during algal bloom and in fall the colonies almost covered the free underside of nearly all stones on the bottom. In winter most of the colonies died out, but scattered individuals were also observed alive during this period. Statoblasts produced in summer were ‘hatching’ in March–April next year. F. sultana seems to feed on all particles that can pass through the mouth opening. A special study regarding this was made on the diatoms, by analysis of fecal pellets. It was found that young colonies of F. sultana filtrated most efficiently the smallest particles (<20 µm) while older individuals in addition were able to elevate the filtration of bigger particles (40–100 µm). The feeding takes place both by filtration by the cilia and by an active use of the tentacles themselves on the lophophore.