Peculiarities of the macro- and micromorphology of the liver of fish of the carp family (Cyprinidae) in a comparative aspect
Authors: Goralskyi L. P. , Demus N. V. , Sokulskyi I. M. , Gutyj B. V. , Kolesnik N. L. , Pavliuchenko O. V. 
Published: July 2024

To assess the ecological and toxicological situation and to determine the impact of various adverse factors on aquatic organisms of the marine environment, it is necessary to conduct morphological studies of those or other organs that are primarily negatively affected. Therefore, we conducted a survey of the structural organization of the liver at the organ, tissue, and cellular levels in the species aspect of clinically healthy freshwater fish of the Carp family: silver crucian carp, common carp, and crucian carp. Fish liver is a parenchymal organ, represented by stroma and parenchyma, which performs various bodily functions, including detoxification. The liver of a fish is a crucial histophysiological marker of the state of the fish organism, as well as its reaction to the environmental background and any external action. In the work, the specific features of the liver morphology of bony fish of the carp family are clarified: silver crucian carp – Carassius gibelio, B. 1782; scaly carp – Cyprinus carpio, L. 1758; spotted carp – Hypophthalmichthys nobilis, R. 1845, which differ in the degree of motor activity in the aquatic environment, nutrition, etc. It was established that in the phylogenetic development of fish that develop in the marine environment, a particular structural restructuring of the liver occurs: adaptations to various living conditions were accompanied by changes in several parameters of the macro- and microscopic architecture of the liver. Silver carp and crucian carp (omnivorous) have two-lobed livers, while variegated carp (herbivores) have three livers. For carp and crucian carp, a characteristic feature of the liver is the presence of a hepatopancreas (liver and pancreas associated in a single organ); in silver crucian carp, they are separated into separate organs. A feature of the microscopic structure of the liver of the carp family is poorly developed interlobular connective tissue, and the parenchyma of the liver lobe has a tubular structure in the form of multifaceted, broken, thick-walled tubules, the walls of which are hepatocytes. According to the results of histometric studies, the average area of the liver lobule associated with accumulations of pancreatocytes (hepatopancreas) in carp was 1294 ± 132 μm², while the area of accumulations of pancreatocytes in the liver lobule occupies 42.4 ± 2.1 μm² (3.27 %). The area ratio of the pancreas to the area of the liver lobe equals 1:29.6. Similar results were found in the spotted carp. At the same time, the area of the liver lobule associated with clusters of pancreatocytes in the crucian carp is 2.35 times smaller than that of the carp and amounts to 552 ± 97 μm² respectively. At the same time, the area of the pancreas in one lobule of the carp liver occupies 13.56 %. The ratio of the area of the pancreas to the total area of the liver lobule is 1:6.4. This structural structure of the liver in carp fish is possibly related to the peculiarities of its vascularization and the type of secretion, etc. It was established that the most significant volume of cytoplasm and karyoplasm was found in silver crucian carp, where it was 12.982 ± 1.420 μm³ and 0.398 ± 0.021 μm³, respectively. The smallest volume of these indicators was found in carp, namely 2.971 ± 0.224 μm³ and 0.212 ± 0.009 μm³, respectively. The smallest nuclear-cytoplasmic ratio was found in silver crucian hepatocytes (0.0316 ± 0.0024). The conducted morphological studies at the organ, tissue, and cellular levels will provide an opportunity to find out the adaptation of the animal body to specific conditions of existence and allow us to determine the influence of environmental factors on the fish body. The results of the morphological study of the structure of the liver of bony fish of the carp family significantly supplement the information on the morphology of the liver in the relevant sections of clinical, comparative anatomy, histology, and forensic veterinary medicine.