Dep. Invertebrate Zoology, St.-Petersburg State University, Universitetskaya nab. 7/9, St.-Petersburg 199034, Russia

Abstract

Individual zooids and colonies of Cristatella mucedo possess the wide spectrum of feeding reactions. "Individual" behavioural reactions include by different tentacle movements: bending, inrolling and unrolling, pushinh particles, pulling the tentacles in a bud-like structure, crossing og lophophore laminas, outrolling of indigestible particles and their flicking away from lophophore, synchronous shivering of all tentacles of the lophophore. Zooids demonstrate various types of cooperative activity: partial or complete subdivision into two filtration layers and formation of continuous filtration zone above colony. The behavioural reactions are considered to increase efficiency and intensity of filtration. In food deficit conditions colonies tend to fragmenting. Density of zooids in new colonies is always higher than that in the old one. At continuous starvation some zooids begins to rezorbe, it is possible that rezorbe materials can be used to maintain vital functions of the colony.