Ecophysiological monitoring of Caspian Sea coastal ecosystems: state of the ichthyofauna in the Siyazan region

This study presents the results of marine monitoring conducted in the Siyazan coastal zone of the Azerbaijani sector of the Caspian Sea. As part of the study, a genotoxic analysis of peripheral blood erythrocytes and a histological examination of the gills and liver of sampled fish were performed. The genotoxic study of erythrocytes revealed a number of morphological aberrations, including micronuclei, nuclear deformation, their atypical intracellular displacement, and changes in the normal shape of erythrocytes; however, the identified indicators of genotoxic alterations were within reference values. Histological analysis of the gills demonstrated changes such as hyperplasia and curvature of the secondary lamellae, adhesions, and fusion of the apical parts of the secondary lamellae. The results of histopathological examination of the liver of the studied fish species revealed alterations such as hepatocyte hypertrophy, sinusoidal dilation, venous congestion, and melanomacrophage aggregates. The observed alterations in blood erythrocytes and histological shifts in the gills and liver of the studied fish can be interpreted as protective-adaptive responses reflecting the impact of environmental factors.