DNA Damage and Immunological Responses in the Whiteleg Shrimp ( Litopenaeus vannamei ) Exposed to Sublethal Levels of Mercury

Litopenaeus vannamei juveniles were exposed to sublethal levels (2.33–18.03 µg/L) of inorganic mercury. Time of exposure (0, 24 and 168 h) was a source of DNA damage. Mean comet tail length not changed significantly with mercury concentrations and exposure time, and this parameter cannot be used to assess DNA damage in this shrimp. Total hemocyte count showed a trend to decrease according to the increase of mercury concentrations, although no significant difference between treatments with mercury was observed. The phenoloxidase (PO) activity was not influenced by the time of exposure. At the end of the experiment, the PO in organisms exposed to 18.03 µg/L was different from the control. The time of exposure has a more important influence in superoxide dismutase than the concentration of mercury. According to these results, a suitable criterion of water quality for long-term exposure of L. vannamei should be lower than 2 µg/L of mercury.