THE HISTOLOGICAL STRUCTURE OF GILLS AND KIDNEYS OF THE PRUSSIAN CARP FROM ZAPORIZHIAN (DNIPRO) RESERVOIR

Abstract

In this article the histological structure of gills and kidneys of the Prussian carp is considered and researched. The research was conducted in the waters of the Zaporizhian (Dnipro) reservoir, namely in the Samara Bay and the lower part of the reservoir (near the village of Viiskove) during 2017–2019. Previous studies have revealed the excess of maximum permissible concentrations of heavy metals in the water of the Samara Bay compared to the lower part of the Zaporozhian reservoir. High levels of nickel and cadmium were observed in the Samara Bay. Statistically significant differences were found between the content of copper, zinc, nickel, lead and cadmium in the two areas of the reservoir (p <0.05). Fish kidneys and gills for histological examination were obtained from fresh fish by anatomical dissection. Histological examinations were performed using generally accepted methods. Histological examination revealed histological changes in the gills and kidneys, manifested in varying intensity. Examination of the Prussian carp gills revealed necrosis in fish from both areas. Moreover, the largest percentage of this pathology occurred in the fall in fish from the Samara Bay. Epithelial hyperplasia was also found in the Prussian carp from the Samara Bay. In the Prussian carp from the lower part of the Zaporizhian Reservoir, the curvature of the lamellae and the thickening of the terminals of the respiratory lamellae were observed. Histological examination of the kidneys demonstrated that the Prussian carp from the Samara Bay, the lumen of the distal convoluted tubule was absent or narrowed, there was swelling of the epithelium and necrosis. Also in fish from both sites there was a degeneration of renal tubules. Moreover, the largest percentage of manifestations occurred in females from the Samara Bay. In general, the most numerous pathology in the Prussian carp of the Samara Bay was the infiltration of blood cells into the kidney tissue. The above pathology was also less common in fish from the lower part. Cystic neoplasms were also found in fish from both sexes in the summer. The expressed variety of the revealed types of histologic disturbances, as a rule, testifies to the chronic negative effect of a complex of adverse environmental factors on an organism of fish. The detected pathologies may indicate the negative impact of heavy metals, as previous researches have shown that the content of most heavy metals in the water of the Samara Bay exceeds the maximum allowable concentrations. Given the data obtained, the Prussian carp can be used as a bioindicator of the aquatic environment, and its organs as a biomarker of the body.