Characterization of the immune response of the north scallop Argopecten purpuratus (Lamarck, 1819) (Mollusca: Bivalvia)

Abstract

The immune response in mollusks has an important role as a defense against bacteriae, fungi, protozoa and metazoans. The hemocytes are responsible for generating different kinds of innate responses such as: phagocytosis, encapsulation and production of cytotoxic substances and antibacterial peptides. Through light microscopy we estimated the hemocyte number using a Neubauer chamber. Over hemocytes monolayers we measured the phagocytic ability on yeasts. The haemolytic activity on rat's erythrocytes was tested by hemoglobin release and the production of anion superoxide was quantified by the reduction of NBT (Nitro Blue Tetrazolium). We determined that the immune system from Argopecten purpuratus was defined by two types of hemocytes: hyalinocytes and granulocytes. The number of hemocytes circulating in the hemolymph showed a seasonal variation, having a greater increase during winter than in autumn. The hemocytes phagocytized yeast in the absence of plasma when they were opsonized, showing a remarkable increase in phagocytosis. Plasma and hemocytes have an equivalent hemolytic ability against rat?s erythrocytes. The hemocytes present production of anion superoxide that increases considerably over the control with the use of zymosan and, decreases with the use of the superoxide dismutase. The results show that hemocytes from Argopecten purpuratus are able to display different defense mechanisms during the cellular response that could be used as tools to evaluate the immune system of mollusks in the near future.