[The Effect of Coprophagy on the Size of Plant Fibers in the Digestive Tract of Hares Lepus europaeus and L. timidus (Lagomorpha, Leporidae)].

We have studied the distribution of plant fibers of different sizes in the digestive tracts of two hare species: the brown hare (Lepus euopaeus) and the mountain hare (L. timidus). In all studied hares (18 specimens), the highest amount of fine-sized fibers (less than 0.25 mm length) was observed in the cecum (50-70% of the total fiber mass). It was found out that the fine-sized content in the digestive tract, and especially in the cecum, is provided not only by the separation mechanism of the colon, but also by coprophagy. It was shown that repeated passage of food through the digestive tract compensates small volume of the cecum and increases the period of digestion of the same portions of food.

[Reduction of plant fibers in the digestive tract of two pika species (Ochotona pallasi and O. dauurica, Lagomorpha, Ochotonidae)].

The distribution of fibers of different sizes in the gastrointestinal tract in two species of pikas--Pallas' pika Ochotonapallasi and daurian pika O. dauurica--was studied. It was established that fibers of small-sized fractions dominated in all organs of the digestive tract of both pika species, the proportion of which in the stomach proved to be even higher than in fine-grinding voles. No distinct changes in the composition of the size fractions of fibers from organ to organ were observed in the studied individuals of both species, which may be due to frequent consumption of finely dispersed cecotrophs by pikas, which enrich the primary chewed food with small fibers.

[The structure of the epithelial surface of the gastrointestinal tract of pikas (Ochotona pallasi and O. dauurica, Lagomorpha, Ochotonidae): functional and species specificity].

The macro- and microrelief of the surface of the digestive tract mucosa of two pika species--Pallas's (Ochotona pallasi) and Daurian (O. dauurica)--were studied in detail using whole-mount preparations and scanning electron microscopy. The structural features of the intestinal mucosal surface specific of mammals, such as the formation of projections on the crest of the cecal spiral fold and microcells in the colonic ampulla, were studied. It was found that the colonic mucosa forms sparse large conical villi in pocket cavities and on the surface of muscle bands. Significant differences in the cecal mucosal relief were found between the species studied. The possible functional significance of the identified morphological features is discussed.

[Morphological provision for the specialization of hares to coprophagy: the architectonics of the mucous surface of the intestine].

The macro- and microstructures of the surface of the mucous membrane of the gastrointestinal tract were studied in detail in two hare species (Lepus europaeus and L. timidus) using scanning electron and digital microscopes. The morphology of the gastrointestinal tract of hares, which is similar in the two species studied, was described in detail. The macrostructure of the inner surface of the ileocecal junction was investigated. The particularities of the architectonics of the mucous membrane of the intestine that are specific for hares were revealed. In the jejunum of both hare species, the mucous membrane is represented by villi with merged bases, which form circular plates. The mucosa of the colon forms large conical villi, the surface of which is scattered with secreting cells. The possible functional significance of the revealed morphological particularities is discussed.

[Reduction of plant fibers in the digestive tract of the moose and the red deer].

A comparative study of the reduction of plant fibers moving in the digestive tract of nine red deer (Cervus elaphus) and six moose (Alces alces) was made. In the winter season, the character of fiber reduction in the moose and the red deer was similar. In the deer obtained in the early autumn, the relative concentration of small-sized fractions was significantly higher. A sharp decrease in the share oflarge-sized fibers was observed in the omasum as compared to the rumen and the reticulum. It was especially pronounced in the deer obtained in September. Deceleration of fibers of large-sized fractions in the rumen and the reticulum and the structure of the reticulo-omasal opening and its functions were considered.

[Isolating structures of gerbils' digestive tract (Gerbillidae, Rhombomys, Meriones) and their functional significance].

The morphology of the digestive tract of three species of gerbils, characterized by different food specialization-Rhombomys opimus, Meriones tamariscinus and M. meridianus--is considered. The correlation between areas of glandular and keratinizing epithelium is variable and depends greatly on the type of stomach filling and distribution of food mass in it. The bordering fold and ileocecaljunction is not only able to isolate the forestomach and caecum significantly but also may be a mechanism of regulation of food movement through the digestive tract. The close location of ileum's opening to the caecum and its outlet to the colon, as well as isolation of caecum's cavity by a circular fold, could provide direct food transit from the ileum to the colon.

[Feeding rate of sibling vole Microtus rossiaemeridionalis and Mandarin vole Lasiopodomys mandarinus].

Consumption of food of different nutritive value by sibling vole Microtus rossiaemeridionalis and Mandarin vole Lasiopodomys mandarinus as a function of housing conditions--in cages or enclosures--was comparatively studied. Experimental groups included 8-14 adult non-reproducing animals of both sexes kept one per cage or enclosure. The rate of food consumption and digestibility were studied by standard methods and the obtained data were statistically analyzed using Statistica 6.0. Significant differences in the rate of food consumption by mandarin voles housed under different conditions as well as in the consumption and digestibility of food of different biochemical composition in both vole species have been revealed.

[Food specialization in ruminants: the role of endosymbiosis in its formation]. / Pishchevaia spetsializatsiia zhvachnykh: rol' éndosimbioza v ee formirovanii.

Peculiarities of endosymbiosis have been studied in four species of ruminant animals with different food specialization (Cervus elaphus, Moschus moschiferus, Carpa sibirica, ans Gasella subgutturosa) using the methods of macromorphology, light and electron microscopy, and histochemistry. The differences in morphology of bacteria from populations inhabiting rumen epithelium of the studied animals have been revealed. The specificity of connection of bacteria with cornified epithelium has been demonstrated. This connection is reflected on the structure of outer epithelium layers. The functional interpretation of gizzard epithelium macrolandscape peculiarities has been improved. An important part of endosymbiosis in evolutionary-morphological transformations of stomach and intestines, and in formation of food specialization in wild animal species has been underlined.