ИСТИНА

The mechanism of radula formation described for different groups of gastropods includes Patellogastropoda (Testudinalia tesulata), Neogastropoda (Conus pulicarius) and Nudibranchia (Flabellina verrucosa) by light, electron microscopy and cLSM. New teeth of radula forms in the end of the radula sheath by specialized cells – odontoblasts. Radula membrane synthesized by membranoblasts. All studied species occur different pattern of radula formation. The differences between renewal of the radula in studied molluscs are in: 1) number of odontoblasts that formed one teeth (from one in F.verrucosa to thousands in T.tesulata); 2) size and shape of odontoblasts (big cuboidal in F.verrucosa, small elongated in T.tesulata and square in C. pulicarius); 3) type of secretion (by microvilli in F.verrucosa, cytoplasmatic protrusions in C. pulicarius and apocrine secretions in T.tesulata); 4) location of the membranoblasts (directly behind the odontoblasts in F.verrucosa, in the some distance of the odontoblasts in T.tesulata and absence in C. pulicarius) and mechanism of attachment to the radula membrane; 5) fine morphology of the youngest teeth (it consist of vesicles in T.tesulata, homogeny structure in C. pulicarius and F.verrucosa); 6) mechanism of maturation. The high morphology diversity of the radula speaks that mechanism of the renewal is unique for the studied groups and combinations of morphology features do not repeat in different mollusks.