ИСТИНА

Onchidorididae (Doridoidei, Nudibranchia) is the family of nudibranch mollusks with spicules in their integuments which bear supporting and protective functions. Despite that general morphology and arrangements of the spicules well described, data of localization, internal morphology and correlations between spicules morphology and strength are fragmentary. This study describes in detail the spicules of three dorid Acanthodoris pilosa (Abildgaard in Müller, 1789), Adalaria proxima (Alder, Hancock, 1854), Onchidoris muricata (Muller, 1776) inhabiting in the White Sea. The collection of material was carried out in the summer period 2016-2019 in the Kandalaksha Bay of the White Sea in the vicinity of the N.A. Pertsov White Sea Biological Station. During the research classical methods of light and scanning electron microscopy were As a result of the study of spicular morphology there were described four types spicules (monoactine, diactine, triactine, tetractine) for all studied species, as well as spherules, which have been found only in papillae of Ac. pilosa. The external and internal morphology of spicules have been studied by scanning electron microscopy. Three types of internal organization of the spicules have been identified – monolithic, mixed, and concentric. There was no find reveal correlation between the type of the spicules and their internal structure. For the first time have been proposed the correlation between the general morphology, thickness of the tracts and thickness of the integuments: the density of the integuments does not depend only on the number of the spicules, but also on the character of their colocalization and the thickness of the layer in which they are located. The specula networks of body Ac. pilosa has thick covers and doesn’t have elongated spicules in the papilla, but O. muricata and Ad. proxima have vertical tracts with elongated spicules in the papilla with thin cover. This work was supported by the RFFR grant №18-05-60158, № 18-34-00251.