Nikitenko E.D., Vortsepneva E.V. 2020. [Spicule complex of three Onchidorididae species (Gastropoda: Doridina) from the White Sea] // Invertebrate Zoology. Vol.17. No.1: 44–58 [in Russian, with English summary].
ABSTRACT: Onchidorididae (Doridina, Nudibranchia) is a family of nudibranch mollusks that contain spicules in their integuments that perform supporting and protective functions. Despite the fact that the presence of spicules for dorids has been noted for a long time, data on the morphology of spicules, the features of their relative positioning and localization in the body is presented only for some species of mollusks. For the first time for three species of the family Onchidorididae — Acanthodoris pilosa (Abildgaard in Mьller, 1789), Adalaria proxima (Alder et Hancock, 1854), Onchidoris muricata (Mьller, 1776) that inhabit the White Sea. In each body parts the prevailing type of spicules was detected, the internal morphology of spicules as well as their relative position and packing method were studied. The presence of monoactine, diactine, triactine, and tetractine spicules, was noted as well as spherical spicules, found only in Ac. pilosa papillae was noted. The external and internal morphology was studied using scanning electron microscopy. Three types of internal organization of spicules were distinguished - monolithic, mixed, concentric. Absence of correlation between the type of spicules and their internal structure has been established. The paper considers the features of the localization of spicules relative to each other, describes specific tracts into which the spicules are organized. For the first time, a correlation between the thickness of the integument and the thickness of the spicular tracts was noted: the density of the covers depends not on the number of spicules, but on the nature of their localization relative to each other (an increase in packing density of spicules due to the complex organization of tetractine spicules and a decrease in the total thickness of the body wall) and on the thickness of the layer that they are located in. Since the organization of spicules can significantly differ even in closely related genuses, the different structure of the spicule complex can be explained by the difference in the biology and ecology of the species.
KEY WORDS: spicule, Acanthodoris, Adalaria, Onchidoris, Nudibranchia, Mollusca.