Specificity of innate immunity in bivalves: a lesson from bacteria

Bivalves are a relevant ecological group, widespread in freshwater, estuarine, and marine ecosystems, with many edible species, such as oysters, mussels, and clams. Bivalves are endowed with an effective and complex innate immune system (humoral and cellular defenses). Bivalve immunity displays a wide variety of sensitive receptors, selective effectors, and synergistic genetic regulatory networks that afford protection in a fluctuating environment.As filter feeders, bivalves accumulate large numbers of microorganisms, mainly bacteria, that can either establish a commensal relationship with the host or proliferate and invade soft tissues, resulting in a high mortality of bivalve juveniles and adults. In this framework, understanding the relationship between the bivalve immune system and bacteria has important implications not only for the protection of economically important species but also for human health concerns. Available data underlying the specificity of bivalve immune responses to bacterial challenges will be summarized. ©2016 Elsevier Inc. All rights reserved.