Long-term administration of diets containing Gracilaria tenuistipitata extract induce the expression of immune-related genes and increase the immune response and resistance against Vibrio harveyi in white shrimp Litopenaeus vannamei

Abstract

White shrimp Litopenaeus vannamei juveniles (2.15 ± 0.16 g) fed diets containing Gracilaria tenuistipitata extract (GTE) at 0, 0.5, 1.0, and 2.0 g kg−1 for 16 weeks were examined for transcripts of lipopolysaccharide and β-1,3-glucan binding protein (LGBP), peroxinectin (PX), integrin β (IB), prophenoloxidase (proPO) I, proPO II, α-2 macroglobulin (α-2 M), cytMnSOD, mtMnSOD, glutathione peroxidase (GPx), transglutaminase (TG) I, TG II, lysozyme, and heat shock protein 70 (HSP70) as well as immune parameters. Shrimp fed the 2.0 g kg−1 GTE diet significantly exhibited up-regulated expressions of these genes, increased hyaline cells (HCs), granular cells (GCs, including semi-granular cells), total hemocyte count (THC), phenoloxidase (PO) activity, respiratory burst (RB), superoxide dismutase (SOD) activity, and earlier hemolymph clotting time. In a separate experiment, shrimp fed different diets for 16 weeks were challenged with Vibrio harveyi at 2 × 104 cfu shrimp−1 and then placed in seawater. The survival rate of shrimp fed the 2.0 g kg−1 GTE diet was significantly higher over 24–168 h post challenge. In conclusion, shrimp following long-term oral administration of a GTE-containing diet at 2.0 g kg−1 induced the expression of immune-related genes and exhibited increased their immune response and resistance against V. harveyi.