Species specifics of morphology of the liver of the fishes of the Cyprinidae family

Abstract

Providing mankind with high-quality products of aquaculture is possible only by introduction of modern industrial technologies to fish farming, growing fish based on modern scientific achievements. Assessment of the ecotoxic situation and identification of impacts of various unfavourable factors of aquatic environment on aquatic organisms should be made through morphological studies of the organs that are first to encounter the impact. The study revealed species specifics of the morphology of the liver of the fishes of the Cyprinidae family – Prussian carp (Carassius gibelio), Eurasian carp (Cyprinus carpio), and bighead carp (Hypophthalmichthys nobilis), which vary by extent of the motor activity in the aquatic environment, nutrition, etc. We determined that during phylogenetic development of fish that grow in the aquatic environment, there occurs a certain restructuring of the liver: the adaptation to various living conditions were accompanied by changes in a number of parameters of macro- and microscopic architectonics of the liver. Cyprinus carpio and Carassius gibelio (omnivores) have a two-lobe liver, while Hypophthalmichthys nobilis (a herbivore) has a three-lobe liver. For C. carpio and H. nobilis, a characteristic feature of the liver was presence of the hepatopancreatitis (the liver and the pancreas, associated into a single organ), and in C. gibelio, they are differentiated into individual organs. A peculiarity of the microscopic structure of the liver of the Cyprinidae family is poorly developed interlobular connective tissue, and parenchyma of the liver lobule has a tubular structure as polyhedral, curved thick-walled tubules, the walls of which are hepatocytes. The greatest amounts of cytoplasm and karyoplasms were seen in C. gibelio, equaling respectively 12.98 ± 1.42 and 0.40 ± 0.02 µm³. The lowest volume of the indicated parameters was in C. carpio, particularly 2.97 ± 0.22 and 0.21 ± 0.01 µm³, respectively. The lowest nuclear-cytoplasmic ratio was observed in hepatocytes of C. gibelio (0.0316 ± 0.0024). The conducted morphological studies at the levels of organs, tissues and cells can reveal how the fishes’ bodies adapt to particular living conditions and impacts of environmental factors.