Role of carcinoscorpin, a haemolymph lectin of horseshoe crab Carcinoscorpius rotundacauda as humoral factor

This study demonstrated that a marine Indian horseshoe crab, Carcinoscorpious rotundacauda showed higher self defence in an experimental infection upon the induction of its circulatory lectin, carcinoscorpin. It resisted an infection with 10 7 live Escherichia coli per crab when the circulatory carcinoscorpin was 8-16-fold higher after administering 2-ketodeoxyoctonate (Kdo) into the live crab. The naive control with its natural level of circulatory lectin could tolerate a maximum infective dose of 106 live E. coli per crab. Bacterial kiliing and phagocytic uptake in association with the isolated crab amoebocytes in an ex vivo system was considerably higher for the lectin opsonized E. coli compared to unopsonized samples. Carcinoscorpin is thus functionally an opsonin in the defence of the primitive marine arthropod, C. rotundacauda, like vertebrate antibody, a humoral factor involved in the defence of the host. The natural capacity for defending an infection with 106 live E. coli per crab suggested that the crabs in the natural habitat hardly face such an infection and is possibly one of the reasons for its survival over millions of years as a living Ibssil