Escherichia coli endotoxin modulates haemolymph-mediated immune system of Achatina fulica (Bowdich 1822)

Abstract

Achatina fulica (Bowdich,1822), is a unique species due to its ability to maintain three different life cycle stages, demonstrating exceptional capability to survive in its environment, despite microbial challenges, for millions of years. The survival of the snail is important for the ecology and should be studied. There is however a dearth of empirical information about the effects of endotoxin on the immune system of Achatina fulica in particular and to what extent the endotoxin can induce the production of immune-related molecules, of diverse significance (when explored) from A. fulica. This research was aimed at investigating the phenoloxidase activity and Escherrichia coli endotoxin-induced hemolymph coagulation in the A. fulica. Fractions of haemolymph from twelve A. fulica snails were exposed to endotoxin while the control was made endotoxin–free (0.002EU/ml). Haemolymph:plasma (2:3v/v) was exposed to different concentrations of endotoxin. The concentration of coagulated protein and activity of phenoloxidase were then determined. In the results, significantly higher endotoxin-induced protein coagulation was observed in the haemolymph fractions (p < 0.05). Maximum protein coagulation in the mixture of HL/plasma 2:3 was recorded. Exposure of the HL/plasma at optimal ratio to varied endotoxin caused linear protein coagulation up to 2.5EU/ml, beyond which it remained unresponsive to further increase in endotoxin doses. The plasma exhibited the highest phenoloxidase activity up till 10 EU/ml. There was endotoxin-induced protein coagulation and phenoloxidase activity which were endotoxin-concentration-dependent. This study has therefore highlighted the roles of coagulation and phenoloxidase reactions in A. fulica immunity and the potential of A. fulica hemolymph as a model for innate immune studies and bioassay development.