Immune toxicity of phenanthrene and its combined effects of white spot syndrome virus on the survival of kuruma shrimp (Penaeus Japonicus)

Shrimp inhabiting coasts that are frequented by humans are exposed to various pollutants. Additionally, viral infections that cause serious damage to shrimp populations have been observed in these environments. The present study sought to evaluate the immunotoxic effects of phenanthrene (Phe), a pollutant detected in coastal environments, on kuruma shrimp (Penaeus japonicus). We further examined the survival of shrimp following combined exposure to Phe (30 or 300 mu g/L) and white spot syndrome virus (WSSV). Results show that exposure to Phe for seven days decreased immune system-related parameters, including total hemocyte count and phenoloxidase activity in hemolymph (p < 0.05). However, these effects were not detected after three days of exposure. Moreover, a combined exposure assay revealed that shrimp mortality increased following exposure to 300 mu g/L Phe and infection with WSSV. The number of WSSV gene copies was also observed to increase in these co-exposed shrimp. Taken together, these results indicate that long-term Phe exposure impairs the immune system of P. japonicus, resulting in fatal proliferation of WSSV. Hence, considering that combined exposure to Phe and WSSV leads to increased mortality of shrimp, it is imperative that the detrimental effects elicited by multiple stresses be considered, and controlled, in areas inhabited by kuruma shrimp.