Abstract

Scallops are bivalve mollusks that belong to the family Pectinidae. Many scallop species are reared since they are considered a great source of low-cost/high quality protein product. Like any farmed aquatic species, scallops are constantly exposed to changing environmental conditions and many microorganisms present in the surrounding aquatic environment. Despite this, scallops generally remain healthy as a result of their efficient defense mechanisms which are orchestrated by the innate immune response. Like all invertebrates, scallop defense focuses on mechanisms of innate immunity, mediated by cellular (immunocompetent cells, the hemocytes, and mucosal surfaces) and humoral (plasmatic molecules) components to defend themselves against pathogens. Scallop immune response is divided into three main stages: (i) recognition of the non-self by pattern recognition receptors (PRRs) and pattern recognition proteins (PRPs), (ii) activation of signaling pathways and the phagocytic process by hemocytes, and (iii) the production of antimicrobial effectors and antioxidant enzymes. This review summarizes the current knowledge on the innate immunity of this phylogenetic group and provides evidence of certain mechanisms involved in defense reactions.