Аннотация:The radula, comprising a chitinous membrane with teeth arranged in longitudinal and transverse
rows, is a characteristic element of the feeding apparatus within the Mollusca. Radular
morphology is particularly diverse in gastropods, in which it has been studied in detail and found
to be a source of traditionally important taxonomic characters. Rhipidoglossan radula, which is
characterized by presence of a central tooth, several lateral teeth, and numerous long marginal
teeth in each transverse row, is found in three different subclasses – Vetigastropoda,
Neritomorpha and “lower” Heterobranchia. Details of radula formation and its ultrastructure have
not to date been studied in any species with a rhipidoglossan radula. Herein we present the data
of complex studies of the radular fine morphology and radular formation in two vetigastropod
species (Puncturella noachina and Margarites helicinus), and one species of Neritimorpha
(Nerita litterata). The radula itself and the radular formation zone were studied using light and
electron microscopy (scanning and transmission), as well as confocal laser scanning microscopy.
The major peculiarity of Vetigastropoda rhipidoglossan radular formation is posterior bifurcation
of the radular formation zone, creating paired horns into which the odontoblasts of marginal teeth
extend. Significant morphological difference in the formation of the radula between Nerita
litterata and two studied vetigastropod species is the absence of external division of the blind end
of the radular sac. Nevertheless division of the formation zone in N. litterata into two partitions
can be seen on histological sections. The marginal teeth of N.litterata are synthesized in these
horns as well as in vetigastropod species. The adaptive features of the formation zone of
rhipodoglossan radula relate to the increase in the secreting surface for the formation of very long
and numerous marginal teeth of a wide radula.
Keywords: ultrastructure, odontoblast, radular formation zone
Acknowledgments: This research was carried out as a part of the Scientific Project of the State Order
of the Government of the Russian Federation to Lomonosov Moscow State University, No 121032300121-
0. Support was provided by the Russian Science Foundation No 21-14-00042.