Аннотация:The radula is a apomorphic character of Mollusca. It is a cuticle structure consisting
of teeth and radular membrane. New teeth of radula are formed in the terminal end of the
radula sheath by specialized cells – odontoblasts. Radula membrane is synthesized by
membranoblasts. Despite of the numerous studies of general morphology of the radula
there are practically no data on fine morphology and mechanism of radula formation. The
fine morphology of radula sheath is described for different groups of gastropods,including
Patellogastropoda(Testudinalia testudinalis), Neogastropoda (Conus pulicarius) and
Nudibranchia (Flabellina verrucosa) by light, electron microscopy and cLSM. All studied
species have different patterns of radula formation. The differences between renewal
mechanisms of the radula in studied molluscs are resulting in: 1) number of odontoblasts
that form one tooth (from one to thousands); 2) size and shape of odontoblasts (big
cuboidal, small elongated and square); 3) type of secretion (by microvilli orcytoplasmatic
protrusions orapocrine secretions); 4) location of the membranoblasts (directly in front
of the odontoblasts orat a distance from the odontoblasts or absent) and mechanism of
attachment to the radula membrane; 5) fine morphology of the youngest teeth (it consist
of vesicles or homogeny structure); 6) mechanism of maturation.The high morphology
diversity of the radula shows that mechanism of the renewal is unique for the studied
groups and combinations of morphology features do not repeat in different molluscs