BEHAVIOR AND SETTLING OF ACTINULAE OF TUB ULARIA-LARYNX (LEPTOLIDA, TUBULARIIDAE)

Actinulae of the sublittoral hydroid Tubularia larynx tear apical aper tures of gonothecae by pulsation of their oral poles, liberate themsel ves and settle on the bottom during the periods of stagnant water (at low or high tide). Actinulae can move over the surface using their ten tacles attaching to the substrate by apical nematocysts. Actinulae do not actively search for a place for attachment being indifferent to th e influence of such ecological factors as light, gravity, currents, su rface structure and relief of substrate, the presence of slimy bacteri al film. It was supported by the study of the distribution of T. laryn x in the White Sea: colonies of this hydroid were found on different s ubstrates (i.e. stones, sand, laminaria stems, shells of molluscs etc. ). Actinulae anchored to substrate and surrounding stones by their abo ral tentacles can endure fast water flows. The steadiness of the larva e to tidal currents makes the prosperity of T. larynx in the sites wit h strong hydrodynamics, where other hydroids are not able to exist, po ssible. After 12h after the liberation from gonothecae, during the nex t period of stagnant water, actinulae attach themselves to substrate b y their aboral pole and turn into primary polypes, which set up new co lonies.