Effect of hypoxic stress on the immune response and the resistance to vibriosis of the shrimp Penaeus stylirostris

The immune response of shrimp exposed to severe hypoxia, 1 mg O2 ml -1 for 24 h, was measured in terms total haemocyte count (THC), differential haemocyte count (DHC), phenoloxidase activity (PO) and respiratory burst by NBT reduction. Results showed that hypoxia induced a significant decrease (P<5%) of the THC due to a significant decrease of semi-granular cells (SGC) (P <5%) and hyaline cells (HC) (P<5%). There was also a decrease in the NBT reduction. On the other hand, PO activity increased significantly (P<1%) and seemed to be related to a lower amount of plasma inhibitors regulating the prophenoloxidase system. Experimental infection with a virulent Vibrio alginolyticus was carried out by intramuscular injection of 2 × 104 colony forming units (cfu) per shrimp. The mortality of stressed shrimp was 48% while the mortality of control shrimp was 32%. This difference was significant (P<1%). The variations of immunological parameters, except for the PO activity, seem to be consistent with the in vivo response against the pathogenic Vibrio. © 1998 Academic Press.