Sublethal responses of the striped mullet (Mugil cephalus L.) to flourene analogs

Abstract

Juvenile striped mullet (Mugil cephalus) were exposed for up to 12 days to 10-10,000 (mu)g/l fluorene and three fluorene analogs (dibenzofuran, carbazole, and dibenzothiophene). These constituents of oil and coal were all acutely toxic to mullet at concentrations below their maximum solubility in seawater. The relative toxicity of the four analogs was related to their lipophilic nature and chemical reactivity. These pollutants were capable of inducing the corticosteroid stress response and resulting secondary stress responses in mullet. Plasma cortisol concentrations were significantly elevated, followed by a rise in plasma glucose. Responses were mild compared to those elicited by physical stress. Liver glycogen content was initially depressed, and later was restored to levels higher than the controls. Minor changes were observed in plasma lipids, with plasma triglyceride concentrations showing a consistent elevation upon exposure to dibenzofuran. Plasma osmolality was not significantly altered. Components of the xenobiotic metabolizing system of mullet were also affected by exposure to the four compounds. Large increases in liver glutathione concentration were observed, along with slight elevations in liver ascorbic acid content and (beta)-glucuronidase activity. The fluorene analogs caused profound behavioral changes, which appeared to be related to a pharmacological effect on brain biogenic amine levels.