ИСТИНА

Annelids (or “polychaetes”) compose significant part of marine bottom ecosystems. Annelids are characterized by metameric body structure, presence of coelomic cavity and a well-developed circulatory system. Combination of these features provides high level of adaptive plasticity and enables development of an effective immune (defensive) system. Organization and functioning of immune system remains one of the least studied problems in invertebrate physiology. Free cell elements of the coelomic fluid, coelomocytes, constitute the main component of immune system in annelids. Coelomocytes offer recognition of foreign material and its subsequent elimination or isolation. Moreover these cells release humoral factors which are involved in immune response providing. Only several species of annelids were described from this point of view, therefore there is no possibility to combine an unified classification of annelids coelomocytes. Nevertheless there actually is high variability in morphology, origin and functions of coelomocytes among the representatives of different families. Arenicola marina, the marine lugworm, is a common annelid species of coldwatered seas tidal zone. We studied morphology of A. marina coelomocytes, their ability to perform phagocytosis and encapsulation of different foreign bodies using light, transmission, scanning and confocal microscopy. Coelomocytes of this species represent a heterogeneous population with at least five cell morphotypes. All of them are able to perform phagocytosis in varying degree. Encapsulation seems to be more specific defensive reaction and involves only certain cell types. Our results create the basis for further experiments on this species.