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White shrimp Litopenaeus vannamei immersed in seawater (35‰) containing Gracilaria tenuistipitata extract (GTE) at 0 (control), 400, and 600 mg/L for 3 h were exposed to 5 mg/L ammonia-N (ammonia as nitrogen), and immune parameters including hyaline cells (HCs), granular cells (GCs, including semi-granular cells), total hemocyte count (THC), phenoloxidase (PO) activity, respiratory bursts (RBs), superoxide dismutase (SOD) activity, lysozyme activity, and hemolymph protein level were examined 24~120 h post-stress. The immune parameters of shrimp immersed in 600 mg/L GTE returned to original values earlier, at 96~120 h post-stress, whereas in control shrimp they did not. In another experiment, shrimp were immersed in seawater containing GTE at 0 and 600 mg/L for 3 h and examined for transcript levels of immune-related genes at 24 h post-stress. Transcript levels of lipopolysaccharide and β-1,3-glucan binding protein (LGBP), peroxinectin (PX), cytMnSOD, mtMnSOD, and HSP70 were up-regulated at 24 h post-stress in GTE receiving shrimp. We concluded that white shrimp immersed in seawater containing GTE exhibited a capability for maintaining homeostasis by regulating cellular and humoral immunity against ammonia stress as evidenced by up-regulated gene expression and earlier recovery of immune parameters.

Abstract: White shrimp Litopenaeus vannamei fed diets containing the hot-water extract of Gracilaria tenuistipitata at 0 (control), 0.5, 1.0 and 2.0gkg−1 for 21days, were exposed to 5mgL−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 6–120h 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 2.0gkg−1 diet had returned to the background values at 12–24h post-stress, whereas the immune parameters of control shrimp had returned to the background values at 72–≥120h post-stress. It was therefore concluded that L. vannamei fed the extract-containing diets at 2.0gkg−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. [Copyright &y& Elsevier]

Abstract: The innate immunity and resistance against white spot syndrome virus (WSSV) in white shrimp Litopenaeus vannamei which received the Gracilaria tenuistipitata extract were examined. Shrimp immersed in seawater containing the extract at 0 (control), 400 and 600 mg L−1 for 3 h were challenged with WSSV at 2 × 104 copies shrimp−1. Shrimp not exposed to the extract and not received WSSV challenge served as unchallenged control. The survival rate of shrimp immersed in 400 mg L−1 or 600 mg L−1 extract was significantly higher than that of challenged control shrimp over 24–120 h. The haemocyte count, phenoloxidase activity, respiratory burst, superoxide dismutase activity, and lysozyme activity of shrimp immersed in 600 mg L−1 extract were significantly higher than those of unchallenged control shrimp at 6, 6, 6, 6, and 6–24 h post-challenge. In another experiment, shrimp which had received 3 h immersion of 0, 400, 600 mg L−1 extract were challenged with WSSV. The shrimp were then received a booster (3 h immersion in the same dose of the extract), and the immune parameters were examined at 12–120 h post-challenge. The immune parameters of shrimp immersed in 600 mg L−1 extract, and then received a booster at 9, 21, and 45 h were significantly higher than those of unchallenged control shrimp at 12–48 h post-challenge. In conclusion, shrimp which had received the extract exhibited protection against WSSV as evidenced by the higher survival rate and higher values of immune parameters. Shrimp which had received the extract and infected by WSSV showed improved immunity when they received a booster at 9, 21, and 45 h post-WSSV challenge. The extract treatment caused less decrease in PO activity, and showed better performance of lysozyme activity and antioxidant response in WSSV-infected shrimp. [Copyright &y& Elsevier]

Abstract: The haemogram, phenoloxidase (PO) activity, respiratory bursts (RBs), superoxide dismutase (SOD) activity, glutathione peroxidase (GPx) activity, lysozyme activity, and the mitotic index of haematopoietic tissue (HPT) were examined after the white shrimp Litopenaeus vannamei had been fed diets containing the hot-water extract of Gracilaria tenuistipitata at 0 (control), 0.5, 1.0, and 2.0 g kg−1 for 7–35 days. Results indicated that these parameters directly increased with the amount of extract and time, but slightly decreased after 35 days. RBs, SOD activity, and GPx activity reached the highest levels after 14 days, whereas PO and lysozyme activities reached the highest levels after 28 days. In a separate experiment, white shrimp L. vannamei, which had been fed diets containing the extract for 14 days, were challenged with Vibrio alginolyticus at 2 × 106 cfu shrimp−1 and white spot syndrome virus (WSSV) at 1 × 103 copies shrimp−1, and then placed in seawater. The survival rate of shrimp fed the extract-containing diets was significantly higher than that of shrimp fed the control diet at 72–144 h post-challenge. We concluded that dietary administration of the G. tenuistipitata extract at ≤1.0 g kg−1 could enhance the innate immunity within 14 days as evidenced by the increases in immune parameters and mitotic index of HPT in shrimp and their enhanced resistance against V. alginolyticus and WSSV infections. Shrimp fed the extract-containing diets showed a higher and continuous increase in the humoral response indicating its persistent role in innate immunity. [Copyright &y& Elsevier]