Oxidative stress responses of the crayfish Procambrus clarkii to Spiroplasma eriocheiris challenge

As a virulent pathogen, Spiroplasma eriocheiris influences most crustaceans, including the freshwater crayfish Procambrus clarkii. The antioxidant enzymes related to oxidative stress during the pathogenesis of S. eriocheiris in the primary target tissues of hepatopancreas and gills from P. clarkii were analyzed at various time intervals post-infection. H.E histopathology and in situ hybridization assays confirmed the S. eriocheiris infection and detected typical histological changes. Compared with the control group, catalase (CAT) activities in both tissues reduced significantly at the early time of S. eriocheiris challenge (P < 0.05), but recovered gradually at the late stage while still lower than the control group in the hepatopancreas (P < 0.05). A similar tendency was observed in the change of superoxide dismutase (SOD) activities. Acid phosphatase (ACP) and alkaline phosphatase (AKP) activities increased considerably and achieved peak values at 7 days post-infection (dpi) in the hepatopancreas and 5 dpi in the gills, but decreased significantly later till 12 dpi in both tissues (P < 0.05). Peroxidase (POD) activities and malondialdehyde (MDA) contents increased dramatically since the first day and kept a high level during the challenge course. The activities of antioxidant enzymes were generally higher in the hepatopancreas than in the gills. These results suggested that S. eriocheiris affected the antioxidative situation and caused oxidative stress and tissue damage by confusing antioxidant enzymes in P. clarkii.