The rhipidoglossan radula: Formation and morphology of the radula in Puncturella noachina (Linnaeus, 1771) (Fissurellidae, Vetigastropoda).

The rhipidoglossan radula, which is characterized by presence of a central tooth, several lateral teeth, and numerous (more than 10) long marginal teeth in each transverse row, is found in three different subclasses, that is, Vetigastropoda, Neritomorpha and "lower" Heterobranchia. Details of radula formation and its ultrastructure have not been studied in any species with a rhipidoglossan radula. For the first time, we present such data for one vetigastropod species, Puncturella noachina. The radula itself and the radula formation zone were studied using light and electron microscopy (scanning and transmission), as well as confocal laser scanning microscopy. We identify the major features of Vetigastropoda rhipidoglossan radula formation, that is: the posterior bifurcation of the radula formation zone, creating paired horns into which the zones of formation of the marginal teeth extend; the supporting structure in the radula formation zone extends ventrally to strengthen this division; the odontoblasts of the marginal teeth form a multi-layered epithelium; membranoblasts do not differ from odontoblasts in ultrastructure; in some membranoblasts and cells of the sub- and supraradular epithelium basal bodies were found in the apical regions of the cells.