EFFECT OF POLYSACCHARIDE GEL FROM THE FRUIT-RIND OF “DURIAN” AS AN IMMUNOMODULATOR IN PENAEUS MONODON (BLACK TIGER SHRIMP)

Abstract

Polysaccharide gel (PG) isolated from the fruit-rind of “durian” (Durio zibethinus Murr.) has been characterized to be a pectic polysaccharide with immunomodulating and bactericidal activities. This study aimed to evaluate the immunostimulating effect of PG, given as a PG additive diet in Penaeus monodon, by observing the increment of immunocompetency and disease resistance in shrimps. PG additive diets were 1, 2 and 3% PG in shrimp diet, while a diet without PG was used in the control. Each group of 20 juvenile shrimps in closed-recirculating treated water system was fed PG additive diets or the shrimp diet in control, for 12 weeks. Total haemocytes count and phenoloxidase activity of the shrimps immunity were examined. Phenoloxidase activity in shrimps fed with 1 - 3% PG and total haemocytes count in shrimps fed with 1 and 2% PG were higher (P<0.05) than those of the controls. The number of surviving shrimps in groups of 12 weeks prefeeding with 1-3% PG increased against the impact of white spot syndrome virus (WSSV) and bacterium Vibrio harveyi 1526 pathogens more than their control groups. Relative percent survival (RPS) values in groups fed 0, 1, 2 and 3% PG were 0, 76, 100 and 83% respectively at day 6 against WSSV infection and 0, 31, 36 and 22% respectively at day 4 against V. harveyi 1526 infection. Prefeeding of 2% PG showed the highest RPS value for disease resistance of shrimps against both viral and bacterial pathogens. These results suggest that a PG additive diet has the potential to increase immunostimulating activity in the juvenile shrimp, Penaeus monodon.