ON THE SEVERTSOV-PLATE FUNCTION INTENSIFICATION PRINCIPLE BY THE EXAMPLE OF THE INTESTINES OF HEPATIC TREMATODE PARAFASCIOLOPSIS FASCIOLAEMORPHA EJSMONT, 1932 (PLATHELMINTHES, TREMATODA)

The study considers morphological and functional features of the intestine of the trematode Parafasciolopsis fasciolaemorpha in the context of its endostation, namely, the bile ducts in the liver of the moose Alces alces (1st order environment), which reveal mechanisms that ensure the parasite adaptation. The intestine of P. fasciolaemorpha is covered with epithelium, while its apical part is represented by thin microvilli, and the basal part contains nuclei and reticular cytoplasm. The epithelium is delimited from parenchyma by a basal membrane of a collagenous nature. Intense bromphenolophilia and toluidinophilia manifested at the apical end of the microvilli indicate the accumulated glycoproteins and involvement in the breakdown of food, as well as in the increase in the enterocyte resistance to antigenic effects of the host and the manifestation of anticoagulant properties. Enterocytes function in analogy with microapocrine secretion, and digestion is mainly parietal (and partially abdominal). The microvilli in the apical part of the intestinal epithelium increase the working surface area and accelerate the processes of parietal digestion with enhancing the trophic processes of the helminth P. fasciolaemorpha to survive in the host organism, which helps small parasites to adapt in the endostation. The study results serve as a clear illustration of the Severtsov-Plate function intensification principle.