The white shrimp Litopenaeus vannamei which is naturally
distributed along the Pacific coasts of Central and South America
has become the most important cultured species worldwide due to
successful development of techniques for manipulating brood
stocks, spawning, and seed production. However, shrimp farming
has suffered great losses due to deteriorated and stressful
environments that lead to the outbreaks of viral disease like white
spot syndrome virus (WSSV), and bacterial disease caused by Vibrio
alginolyticus and V. harveyi [3,4]. Therefore, maintaining good pond
condition, preventing disease outbreaks, and enhancing immunity
are of primary concern. Several polysaccharides derived from
bacteria like b-glucan, lipopolysaccharide (LPS), peptidoglycan, and
those derived from seaweed like alginate and carrageenan are
considered immunostimulants, and their abilities to activate the
innate immunity of teleost and shrimp have been studied in vitro
and in vivo [5e7].