Acute effect and histopathological evaluation of larvae of the marine kingfish Odontesthes argentinensis exposed to the soluble fraction of oil, diesel and gasoline in water
Petroleum hydrocarbons are considered to be one of the main pollutants in water media. However, studies on the toxicity of these compounds on the early stages of development in fish native to Brazil are scarce. The objective of this work was to evaluate the median lethal concentration (CL50-96h) and the histopathological effects of the soluble fraction (FSA) of oil, diesel and gasoline in water, on larvae of the marine kingfish Odontesthes argentinensis. For the performance of acute toxicological tests, the following concentrations were used: Brazilian oil (5%, 10%, 25%, 50%, 75%, and 100% FSA), diesel (1%, 2%, 4%, 8 %, 16%, 32%, and 64% FSA) and gasoline (1%, 2.5%, 5%, 10%, and 20% FSA), plus the addition of the control for each pollutant. All treatments were performed with three replications and 30 larvae.After carrying out the toxicity tests (96 h), three larvae of each concentration were collected for histological study. The FSA for oil had a CL50-96h equal to 70.68% (65.73–76.01), while diesel and gasoline had a CL50-96h value of 13.46% (10.19-17, 79) and 5.48% (4.85-6.20), respectively. Histological evaluation of O. argentinesis larvae exposed to FSA of oil, diesel and gasoline showed lesions in the gills, pseudobranchs, esophagus and liver. The gills, pseudobranchs and esophagus showed hyperplasia in their epithelia, while the liver presented dilation of the hepatic sinusoid, hepatocytomegaly, binucleation and nuclear degeneration of hepatocytes, as well as pycnotic nuclei.The present study demonstrated that diesel and gasoline are at least five times more toxic than Brazilian oil, however, all pollutants induced moderate histopathological lesions in O. argentinensis larvae.