Immunomodulation by carrageenans in the white shrimp Litopenaeus vannamei and its resistance against Vibrio alginolyticus

The total haemocyte count (THC), phenoloxidase activity, respiratory burst and phagocytic activity and clearance efficiency to Vibrio alginolyticus were examined when the white shrimp Litopenaeus vannamei were injected with different types (type I to type V) of carrageenan at 6 µg g− 1 shrimp. Results showed that the THC, phenoloxidase activity, respiratory burst, and phagocytic activity against V. alginolyticus were significantly higher in shrimp that received any type of carrageenan after 24 h. Results also showed that the THC and PO activity maintained significantly higher in shrimp that received type IV carrageenan as compared to those that received other types of carrageenan after 96 h. In a separate experiment, L. vannamei which had been injected with different types of carrageenan after 3 h were challenged with V. alginolyticus at 7.34 × 106 cfu shrimp− 1, and placed in seawater. The survival of shrimp that received type IV carrageenan was significantly higher than that of shrimp that received type I, II, III and V carrageenan, and shrimp that received saline as well as the control shrimp after 120 h. It was concluded that L. vannamei that received type IV carrageenan (λ-carrageenan) exhibited higher immune ability of L. vannamei as well as resistance against V. alginolyticus infection.