Dietary administration of a Gracilaria tenuistipitata extract produces protective immunity of white shrimp Litopenaeus vannamei in response to ammonia stress

Abstract

White shrimp Litopenaeus vannamei fed diets containing the hot-water extract of Gracilaria tenuistipitata at 0 (control), 0.5, 1.0 and 2.0 g kg(-1) for 21 days, were exposed to 5 mg L-1 ammonia-N (ammonia as nitrogen), and immune parameters, including hyaline cells (HCs), granular cells (GCs, including semi-granular cells), the total hemocyte count (THC), phenoloxidase (PO) activity, respiratory bursts (RBs), superoxide dismutase (SOD) activity, and hemolymph protein level, were examined 6-120 h post-stress. Shrimp fed the control diet with no ammonia stress served as the background control. Results indicated that the immune parameters of shrimp fed the 2.0 g kg(-1) diet had returned to the background values at 12-24 h post-stress, whereas the immune parameters of control shrimp had returned to the background values at 72->= 120 h post-stress. It was therefore concluded that L. vannamei fed the extract-containing diets at 2.0 g kg(-1) or less exhibited a protective effect against ammonia stress as evidenced by the earlier recovery of immune parameters. Shrimp subjected to ammonia stress showed a greater decrease in PO activity and later recovery to the background value compared to the decrease and recovery of RBs and SOD activity indicating progressive perturbation of the humoral immunity. (C) 2012 Elsevier B.V. All rights reserved.