Biomarcadores genotóxicos e histopatológicos de quatro espécies de peixes com diferentes hábitos alimentares do médio Rio São Francisco

Abstract

Fish with different feeding habits absorb varying amounts of environmental pollutants, which can occur through respiratory, dermal, or digestive pathways and accumulate in various tissues. The occurrence of both genotoxic and histopathological alterations may be related to the feeding habits and trophic levels occupied by the fish. In this study, four fish species, Salminus franciscanus (carnivore), Prochilodus argenteus (detritivore herbivore), Myleus micans (herbivore), and Leporinus obtusidens (omnivore), occupying different trophic levels in the middle São Francisco River area, Januária, Minas Gerais, were compared. The researchers analyzed the occurrence of micronuclei (MN) and morphonuclear alterations (AMN), as well as the presence of different liver damages, among the four fish species. They expected that (i) fish occupying different trophic levels would show different amounts of micronuclei and morphonuclear alterations such as blebbed, lobed, notched, and eight-shaped, as these damages are related to the presence of environmental contaminants, and (ii) fish occupying different trophic levels would exhibit varied liver damages, such as hydropic degeneration, steatosis, hemosiderosis, hyperemia, inflammation, and necrosis, since the liver is an important organ for detoxification in living organisms, reflecting the presence of contaminants in the aquatic environment. For cytogenetic analyses, the micronucleus test (MN test) was conducted, considering the quantification of AMN. Histopathological analyses were performed based on photomicrographs of permanent histological slides from random fields of hepatic tissue. The different fish species were ordered based on the genetic alterations and liver damages using distinct principal component analysis (PCA). Two biplot graphs were generated to show the projection of the original axes on a scatter diagram. The scores of the two main axes of these PCAs were extracted and compared among the four fish species using generalized linear models (GLM). The fish species were the explanatory variables in these models, and the PCA scores related to genetic alterations or liver damages were the response variables, following a Gaussian distribution. Analysis of variance (ANOVA) with F-tests was used to test the significance of the models. Contrast analyses were calculated to group statistically equal levels and separate statistically different ones. The software used for the analysis was Past (Paleontological Statistics Software) version 4.03 and R Core Team, 2023. The results indicated that P. argenteus had the highest number of MN, while M. micans and S. franciscanus had the highest quantities of AMN. The lowest AMN scores were observed in L. obtusidens and P. argenteus. The researchers also compared the indices of liver damages among these same species, and the results showed that S. franciscanus and L. obtusidens were most affected by degenerative liver lesions. P. argenteus had the highest score for necrosis, a type of cell death. The findings indicate a strong correlation between the levels of cytogenetic and histopathological damages with the feeding diet and trophic levels occupied by the evaluated fish species.