ИСТИНА

Nematode midgut is a straight tube made up of monolayer of epithelium. Marine free-living nematode species differ from one another in diet and ways of food ingestion that could be reflected in fine structures of the midgut cells, we expect; another possible expectation is the structure of the midgut cell is linked with taxonomic position of species. We studied ten species of White Sea nematodes from five orders: Bathylaimus arcticus (Enoplida, Tripyloididae), Oxystomina sp. (Enoplida, Oxystominidae), Paracanthonchus caecus (Chromadorida, Cyatholaimidae), Halichoanolaimus robustus (Chromadorida, Selachinematidae), Desmodora communis (Desmodorida, Desmodoridae), Draconema ophicephalum (Desmodorida, Draconematidae), Paramonhystera filamentosa (Monhysterida, Xyalidae), Sphaerolaimus balticus (Monhysterida, Sphaerolaimidae) Odontophora deconinki (Araeolaimida, Axonoilaimidae) and Sabatieria ornata (Araeolaimida, Comesomatidae). Intestine structures such as glycocalyx, apical microvilli, features of digestive vacuoles and lipid drops, development of endoplasmic reticulum, distribution of mitochondria and even number of cells on a cross-section varies significantly among species. There is a rather weak correlation between glycocalyx structure and diet: species igesting coarse items but having no buccal armament for precursory treatment of food tend to have thick and complicated glycocalyx while those sucking out soft luquid content of injured hard-shelled items mostly haver thinner amorphous glycocalyx, Ciliate- and bacteria feeders have an intermediate or peculiar glycocalyx type. Link of the diet with internal cell structures is less evident and probably determined biochemical traits of food item. The study is supported by Russian Foundation for Basic Research, grant No. 15-04-02597.