ИСТИНА

Odontophora deconincki is a common White Sea species living in surface sand layer in the intertidal zone. It can be characterized as epigrowth-feeder according to classification of Wieser (1953). Buccal cavity is composed of hemispherical cheilostom and elongated pyramidal trihedral pharyngostom. Cheilostom is armed with six equal claw-like odontia which stick out radially like a flower when mouth is is opened. Pharyngostoma consists of gymnostoma and stegostoma which are equal in length and differ scarcely from one another in ultrastructure, Diagonal muscles promote opening of mouth. Sparse muscle cells adjacent to basal membrane are found around the pharynx. Midgut consists of six to seven trapezoidal cells on cross section. Spherocrystalls are most peculiar structure in the cells. They apparently are dynamic structures like lysosomes on early digestive stage. Microvilli cylindrical. Glycocalyx varies from amorphous to multilamellar, probably due to stage of food digestion. The study is supported by Russian Fund of Fundamental Researches, grant N 15-04-02597. Department of Invertebrate Zoology, Faculty of Biology, Lomonosov’s Moscow State University, Moscow, Russia. E-mail: mariaf92@mail.ru