The use of diatoms (Amphora sp.) As immunostimulant in pacific white shrimp (Litopenaeus vannamei) diet

Abstract

Amphora sp. is one of the interesting microalgae due to its rapid growth, high lipid content, ranging from 40-60% of dry biomass, suitability as live food for commercial aquatic animal larvae such as shrimp and abalone. The objective of this study is to evaluate the potential of Amphora sp. isolated from four different locations in the Gulf of Thailand: Sichang Island (ASC), Samae Sarn Island (ASS), Pranburi (APB), and Laem Yai (ALY) as immunostimulant in Pacific white shrimp (Litopenaeus vannamei) diet. Four Amphora sp. isolations were cultured and compared productivity. The results showed that ASC and ALY had higher productivity, lipid content and polyunsaturated fatty acid composition compared to the other 2 strains. These ASC and ALY were chosen for optimum culture condition experiment, varied with 3 light intensities and 2 medium concentrations. The results showed that ALY cultured with medium light intensity with F/20 medium can produce higher biomass, saturated fatty acids, and important unsaturated fatty acids than the other culture condition. Shrimp fed with 15% of this Amphora sp. for 6 weeks demonstrated the higher survival rate from challenge test than 3 weeks. In addition, the expression of LvALF gene that response for Anti-lipopolysaccharide factors in hepatopancrease have been found. This finding indicated that adding 15% Amphora sp. in shrimp diet may enhance immunity of shrimp infected with V. parahaemolyticus. However further study in immune parameters such as PO and SOD must be included to clarify the mechanism of shrimp immune system.