Assessment of immune status of yellowfin seabream (Acanthopagrus latus) during short term exposure to phenanthrene

The aim of the present investigation was to assess the immune status in yellowfin seabream (Acanthopagrus latus) exposed to different concentrations of phenanthrene (Phe) for 14 days. In addition, the Phe accumulation in the fish muscle was measured during the experiment. Fish were injected with different concentrations (0, 2, 20 and 40 mg/kg) of Phe and samples were taken from tissue and blood of fish 1, 4, 7 and 14 days after injection. Exposure of fish to Phe caused a significant decrease in white blood cells, C3 and C4 levels, lysosomal membrane stability, lysozyme activity after 4 days and antibacterial activity after 7 days of the experiment. In contrast, cortisol level significantly increased after 4 days. The concentration of Phe in fish muscle increased rapidly after 4 days. The main tissue changes observed in the head kidney including increase in melanomacrophage centers (MMCs), empty spaces between cells and hemorrhage. The degree of tissue changes ranged from normal to moderate in Phe-treated fish. The size and number of MMCs in treated fish were significantly higher than control. In conclusion, Phe toxicity in yellowfin seabream can induce increased cortisol level, tissue changes and immune suppression.