Histopathological effects of chronic larval exposure of the marine kingfish Odontesthes argentinensis to the water-soluble oil fraction (WSF)

Author: Emeline Pereira Gusmão (Currículo Lattes)
Supervisor: Dr Kleber Campos Miranda-Filho

Abstract

For decades, oil has been the main source of energy for humanity and has figured as one of the main pollutants found in aquatic resources. Records of oil spills in the southern region of Brazil are scarce, but there are risks due to the activity of ports and industries related to oil. The marine kingfish Odontesthes argentinensis is distributed from São Paulo to southern Argentina, where it is an important fishing resource and has been considered for aquaculture. The acute and chronic toxicity of the water-soluble fraction (WSF) of oil was evaluated on growth and histopathological effects in O. argentinensis larvae. Larvae of 17 days were exposed to concentrations of 5%, 10%, 20%, 40%, 60% and 100% of the WSF, added to the control group, for 96 h in an acute experiment.The median lethal concentration (LC50) was estimated at 55% of the WSF and the safety level at 5.5% of the WSF. The chronic toxicity test was conducted with newly hatched larvae that were exposed to sublethal concentrations (2.5%, 5%, 10% and 20% of the WSF), plus the control without adding the oil WSF (all with three replicates) in a semi-static system for 21 days. The survival and growth of larvae exposed to 20% of the WSF were significantly lower than the other concentrations. Histopathological alterations were found in the gills (hemorrhage, lamellar telangiectasia, necrosis, hypertrophy and hyperplasia), in the liver (basophilia, hypertrophy, karyosis, karypicnosis) and in the kidneys (nuclear alterations and enlargement of the glomeruli). Kingfish larvae can suffer damage that indicates the severity of possible exposure to the WSF from oil.The histopathological biomarker proved to be quite sensitive in relation to the acute and chronic exposure of O. argentinensis to oil.

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