Histological and ultramicroscopic features of the liver of Hypophthalmichthys nobilis

To determine the ecological and toxicological situation and assess the impact of various adverse factors in the aquatic env i ronment on aquatic organisms, a morphological analysis of specific organs, which are primarily subjected to adverse effects, should be conducted. Histological and ultramicroscopic features of the liver structure in the fish of the carp family, specifically the bighead carp – Hypophthalmichthys nobilis (Eschmeyer, 2003), are considered in this paper. An analysis of the microstru c ture of liver tissue was carried out using light microscopy and ultramicroscopic methods, which enabled us to identify the organ's key morphological and functional features. It was established that during the phylogenetic development of fish that grow in aqu a tic environments, specific structural rearrangements of the liver occur: adaptations to various living conditions were accompanied by changes in several parameters of liver morphology. In the bighead carp (herbivorous), the liver is trilobed. A characteristic feature of the bighead carp liver is the presence of a hepatopancreas (liver and pancreas associated as a single organ). A distin c tive feature of the microscopic structure of the liver in the carp family is the poorly developed interlobular connective tissue. In contrast, the parenchyma of the liver lobule has a tubular structure consisting of polygonal, irregular, thick-walled tubules whose walls are formed by hepatocytes. These tubules are represented by sinusoidal capillaries, which ensure efficient exchange of substances between the blood and liver cells, aiding in the detoxification and processing of nutrients. Large glycogen reserves are also observed in these tubules, indicating a high level of metabolic activity and the ability of the carp liver to accumulate energy resources. The state of hepatocytes, the liver's vascular system, and structural changes resulting from various ecological and physiological factors were investigated. The main adaptive mechanisms of liver tissue, which ensure its functional activity in bighead carp, were identified. The results of this study expand and complement the knowledge of the macro- and microscopic structure of the liver concerning the species characteristics of the bighead carp, contributing to our understanding of its anatomy, histology, comparative anatomy, zoology, and more.