Immunity in Molluscs: Recognition and Effector Mechanisms, with a Focus on Bivalvia.

The study of the molluscan immune systems, and in particular those of bivalve molluscs (clams, oysters, scallops, mussels) has experienced great growth in recent decades, mainly due to the needs of a rapidly growing aquaculture industry to manage the impacts of disease and the application of –omic tools to these diverse group of non-model invertebrate species. Several unique aspects of bivalve immune systems highlighted in this chapter include the roles of biomineralization and feeding behavior on mucosal immunity, the discovery of unique levels of diversity in immune genes through lineage-specific expansion of gene families, and indications of trans-generational immune priming. Comparative functional studies using natural and selectively-bred disease resistant strains and species of bivalves and application of gene editing technologies, still to be fully developed for bivalves, should provide exciting insights into the functional relevance of immune gene family expansion in bivalves. Other areas of bivalve immunity that deserve further study include elucidation of the process of hematopoiesis, the molecular characterization of hemocyte subpopulations and mechanisms for immune priming.