Seasonal Differences in Water Pollution and Liver Histopathology of Iberian Barbel (Luciobarbus bocagei) and Douro Nase (Pseudochondrostoma duriense) in an Agricultural Watershed

Abstract

Histopathology has been used as a very useful tool to provide information on the severity of tissue damage, injuries, and organ functionality. Thus, this work aimed to assess whether seasonal variations (summer and winter) in water quality had consequences on the liver histology of Iberian barbel (Luciobarbus bocagei) and Douro nase (Pseudochondrostoma duriense). The research was carried out in the Vilariça River, a tributary of the Sabor River in Portugal, which is used as spawning grounds by these endemic cyprinids. The liver histopathological changes, assessed through a semi-quantitative system, allowed the identification of 13 histopathological changes located in the hepatic parenchyma, bile duct, and blood vessels. The histopathological changes with a higher prevalence in both species were vacuolization of hepatocytes, endothelial rupture, necrosis, fibrosis, and degenerative vacuolization. The results showed that the severity degree of liver histological alterations ranged between moderate and severe, and the major severity degree was observed in L. bocagei, in the summer season, and at the sampling points located in the downstream and middle stream. The canonical analysis indicated that the exposure of fish to metals may increase the potential risk of liver damage. Thus, in the summer, the high concentrations of Fe, Cu, Zn, As, and Mn justified the prevalence of the biliary duct epithelial detachment, in both species, and the hyperplasia of biliary epithelium, in L. bocagei. In the winter, the high TSS and Cd, Ni, and Cr concentrations justified the prevalence of congestion of blood vessels and degenerative vacuolization in both species. The higher hepatosomatic index of fish caught in the winter was due to the high presence of degenerative vacuolization and hepatocyte vacuolization. The severity of liver histopathological changes reflected differences in the type of contaminants in different seasons and sampling periods, and was thus proven as a valuable indicator of water quality.

Cytotoxic Effects of the Atrazine Herbicide on Erythrocytes and Liver Damage in Lithobates spectabilis

“…Consistently with this idea, we observed infiltration of lymphocytes in the liver parenchyma in the present study. These results coincide with the analyses reported on fish [63] and frogs [57] exposed to insecticides, and they may be due to atrazine's ability to induce an immune response. In addition, lymphocyte infiltration is related to inflammation, edema, fibrosis, and liver degeneration [63].…”

“…Accordingly, this damage can obstruct circulation and block blood flow [72]. In the present study, we observed congestion of the blood vessels, which corresponds to findings in other aquatic organisms [63]. Liver analysis determines that the congestion of blood vessels could also cause hepatocyte degeneration and necrosis [67,73].…”

“…We also found a larger area occupied by melanomacrophages upon atrazine Gesaprim® exposure, which could have been due to the activation of a defense mechanism to eliminate atrazine, as has already been reported in fish [54,58]. Organisms may undergo hematological changes to cope with pollutant stress [36,40] after an inflammatory process [63]. In this sense, liver damage caused by atrazine could increase susceptibility to diseases, as occurs in fish living in polluted environments [64], because melanomacrophages act as a defensive system and trap antigens for lymphoid cells in fish and frogs [57].…”

“…In fact, biliary epithelial hyperplasia may be associated with fibrosis, inflammation, and proliferation or may be the result of atrazine. In fish, bile-duct-epithelium hyperplasia is caused by exposure to environmental contaminants [63,72]. Accordingly, this damage can obstruct circulation and block blood flow [72].…”

Differential sensitivity of offspring from four species of goodeine freshwater fish to acute exposure to nitrates

“…Inside the body, NO 3 -N causes physiological and behavioral alterations (Torno et al, 2018;Yang et al, 2019;Yu et al, 2021). The liver is the detoxifying organ and its condition indicates environmental quality (Corredor-Santamaría et al, 2021;Tramunt et al, 2021;Santos et al, 2022). Toxic pollutants cause functional alterations of the gills and liver, such as gas exchange failure and metabolic damage.…”