SIZE-DEPENDENT HEMAGGLUTINATING ACTIVITY IN THE HEMOLYMPH FROM SUB-ADULT BLUE SHRIMP (PENAEUS-STYLIROSTRIS STIMPSON)

1. The blue shrimp (Penaeus stylirostris) haemolymph is capable of agglutinating the red blood cells of several vertebrates to different titres. However, the haemagglutinin is considered non-specific because it is incapable of differentiating erythrocytes of human blood types A, B and O. 2. Haemagglutinating activity and serum protein content were determined for male and female blue shrimp ranging in size from 8.5 to 16 cm. Haemagglutinating activity decreased significantly with animal size, while protein content was unaffected. 3. The above finding is probably related to maturation of the immune system and could explain the higher susceptibility of young shrimp to parasitic and viral diseases.