Toxicological evaluation of Mugil platanus mullet exposure to the water-soluble oil fraction
Human development has contributed to the increase in pollutant levels in aquatic environments. Among the main pollutants found in water bodies, petroleum hydrocarbons stand out. Faced with the problems of degradation of aquatic ecosystems, new species are being tested as possible indicators of environmental integrity. The present study determined the median lethal concentration (LC50) for Mugil platanus species against acute exposure to the water-soluble oil fraction (WSF). Histopathological studies and the analysis of the frequency of micronuclei were also observed in a chronic test. Mullet juveniles (25 ± 2.3 g) were exposed to three chronic concentrations (1.7, 3.5 and 7%), plus the control group for 14 days with an additional 7 days of clearance period (without WSF). Throughout the experimental period (24, 96 h,14 and 21 days) blood samples were collected from the caudal vein for observation of micronuclei (CM) and samples of liver and gills for visualization of histopathologies. For these procedures, seven fish were sampled per tested concentration. The LC50 for 96 h was estimated at 37.5% of the WSF and the safety level at 3.5% of the WSF. The time required for the formation of CM was 96 h of exposure. The clearance time was sufficient for the erythrocyte frequency similar to that of the control group to be reached. Histopathological studies have indicated severe changes in gills and liver tissue. Telangiectasis was the most relevant branchial histopathology. Liver histopathologies such as cholestasis, sinus dilation and inflammatory infiltrates were commonly observed.The micronucleus test and histological study effectively detected some damage caused by the chronic exposure of juvenile mullet to the WSF.