Biomarcadores histopatológicos em zebrafish (Danio rerio) usados no biomonitoramento em córregos urbanos de Campo Grande – MS

Abstract

The aquatic biota is constantly exposed to many toxic substances resulting from human activities that have been altering the physical-chemical and biological processes of water sources. However, this contributes to the reduction of environmental quality, as it can also compromise the health of the living being that inhabit these ecosystems. In this sense, biomonitoring based on aquatic organisms (bioindicators) makes it possible to detect the effects of toxic compounds that may be present in the aquatic ecosystem. Thus, this work aimed to use Danio rerio as an environmental bioindicator to analyze the effects of water from different urban aquatic environments in the city of Campo Grande - Mato Grosso do Sul in a passive biomonitoring system, comparing the temporal dynamics of morphological markers erythrocytes, branchial and hepatic histology, and the concentration of non-protein thiols (muscle fragment) in specimens exposed and not exposed for 3, 6 and 12 days. All streams showed different qualitative characteristics regarding physical-chemical parameters. The presence of metals such as Mn, Zn, Fe, Cr, and Al, in addition to pH, temperature, and nitrite, explained 35.1% of the variance, while total solids, electrical conductivity, ammonia, nitrite, and dissolved oxygen explained 27.6%, for through PCA analysis. Specimens exposed to the waters of the three streams showed significant differences between controls for the frequency of erythrocyte nuclear abnormalities, gill and liver histopathological profile, through the histological alterations index (AHI) and concentration of non-protein thiols (NPT). Our results support previous studies that recorded anthropic effects on the aquatic environment in urban streams. Three days of exposure were enough to cause morphological damage in the erythrocyte nuclei and histopathological markers such as proliferation, desquamation, and necrosis of the primary lamellar epithelium; fusion and aneurysms in the secondary lamellar epithelium. In the liver, degenerative nuclear figures were observed after three days of exposure, followed by hepatocellular hypertrophy, lipidosis, and necrosis at 12 days. The employed biomonitoring model allowed comparing the temporal dynamics of different health markers, using zebrafish as an environmental bioindicator. Future studies may improve this model for other aquatic environments in order to support new approaches to biomonitoring studies.