ИСТИНА

The general morphology of the buccal complex of Flabellina verrucosa (M. Sars, 1829) (Opisthobranchia, Gastropoda) was studied using 3-D reconstruction by semithin sections, scanning electron microscopy (SEM) and laser scanning confocal microscopy (sLCM). F. verrucosa is a common nudibranch species in the White Sea living from intertidal to upper sublittoral zone. The main food objects of F. verrucosa are different hydrozoans, especially members of genera Obelia, Laomedea, Tubularia and Ectopleura. Buccal complex of F. verrucosa is oval structure located in the head and covered by mesenchim tissues. Buccal complex attached to the body wall by thin fibres and includes two strong jaw plates with masticatory board, three groups of thick intrinsic buccal musculature and radular apparatus, which consists of radular sac and odontophore. The jaws very well developed and cover buccal complex like helmet. One group of buccal muscles continues from internal surface of the jaw plate to odontophore, other one from odontophore to radula and the third one connects these two groups of muscles. In the distal part of radular sac large and synthetically active cells: odontoblasts and membranoblasts were found. The radula contains 15-21 rows with three denticles in each row. The central denticle formed by one odontoblast, lateral denticles form by group of cells. The detailed study of fine morphology of the buccal complex is done for Gastropoda for the first time.