EPIZOIC ASSOCIATIONS AMONG THE WHITE SEA HYDROIDS

The epizoic hydrozoan fauna established on other hydroids comprises tw enty four species from nine families in the White Sea. Epizoic hydroid s and their hosts are considered as multilevel epizoic complexes, with the hydroid host as the first level, hydroids colonizing a host, as t he second level, and species established on other epizoic colonies, as the higher levels. The colonial structure of epizoic hydroids is so v aried and flexible that the morphology of some species differs from th eir accepted descriptions. This colonial plasticity is varied in accor dance with a host's structure, and is an evident adaptation to an epiz oic mode of life. Epizoic hydroids. rising above the bottom, not only colonize a new substrate and escape compexitively superior benthic org anisms, but also feed on plankton in tidal currents and local water mo vements caused by the host's hydranths. The hydranth sizes of hydroids combined in one epizoic complex, are different possibly to reduce com petition for food. Epizoic hydrozoan complexes capture planktonic orga nisms of a wide size range, thus becoming integrated modules in epiben thic food webs.