Digestive system of the hepatotrematode Parafasciolopsis fasciolaemorpha Ejsmont, 1932 (Plathelminthes, Trematoda): morphofunctional organization, histological and histochemical features to adaptive specialization

The purpose of the research is to study the morphofunctional organization, histological and histochemical features of the digestive system of the marita Parafasciolopsis fasciolaemorpha, which provide adaptation to parasitism in the endostasis – the liver Alces alces.Materials and methods. Mature specimens of the trematode P. fasciolaemorpha (Ejsmont, 1932) collected from the bile ducts of the Alces alces liver served as the material. Maritas were fixed in 70 and 80% alcohols, Schaffer alcohol-formalin 1 : 9, and 10% neutral formalin. Histological stains: with hematoxylin-eosin and by the Mallory method, followed by additional staining of the nuclei with Orta lithium carmine. Histochemical stains: sublimate-bromophenol blue according to Bonheg, Schick reaction according to McManus with additional staining of nuclei with Mayer's hemalaune, alcian blue according to Steedman and Mowry (pH 3.0 and 2.2) and toluidine blue (pH 2.0-5.0).Results and discussion. Parafasciolopsis fasciolaemorpha (Ejsmont, 1932) is the most pathogenic hepatoparasite of Alces alces L. The study of the features of the morphological organization of the digestive system as one of the border systems of the organism of the parasite revealed a number of features: the muscles of the large oral sucker contain many total proteins, which is confirmed by intense bromophenolophilia; in the thickness of the sucker wall there are small secretory cells and neurosecretory cells with abundant alcian- and toluidinophilic vacuolated cytoplasm; the presence of single and grouped digestive glands located in the parenchyma at the junction of the prepharynx to the pharynx, and on the border between the pharynx and the esophagus; in the apical part of the intestinal epithelium, a “brush border” is formed, the thin microvilli of which contribute to an increase in the working surface of parietal digestion in P. fasciolaemorpha, enhancing the trophic processes of the helminth to survive in the body owner. The revealed histological and histochemical features of the parafasciolopsis digestive system can be considered as examples of adaptive specialization at the site of endostasis.