A comparative analysis of immune memory in bivalve and gastropod Mollusks: From mechanistic insights to practical applications

Mollusks play essential ecological roles in marine and freshwater ecosystems, with their diversity reflected not only in morphological structures but also in immune strategies. Although traditionally considered to possess only innate immunity due to the absence of a typical adaptive immune system, recent studies have revealed that certain mollusks, such as oysters, exhibit “trained immunity”-an enhanced response upon secondary exposure to pathogens. This review summarizes the latest research advances on the immune systems of bivalve and gastropod mollusks, covering both humoral and cellular immunity, with a focus on systematically comparing their commonalities and differences in immune memory mechanisms. Core mechanisms include immune gene expression reprogramming, epigenetic modifications, metabolic reprogramming, and functional differentiation of immune cells. Bivalves primarily rely on complement and lectin pathways, while gastropods are characterized by the involvement of fibrinogen-related proteins (FREPs) and specific lectins. Transgenerational immune priming (TGIP) has been confirmed in bivalves, whereas relevant studies in gastropods remain limited. Furthermore, this review highlights the potential applications of immune memory in aquaculture disease management, such as developing immunostimulatory strategies to combat pathogens like Ostreid herpesvirus 1 (OsHV-1). A deeper understanding of the underlying mechanisms is expected to advance the development of immune-enhancing approaches. • Epigenetic H3K4me3 drives oyster immune memory, enhancing disease resilience. • Bivalves' complement vs. gastropods' FREPs reveal tailored immune strategies. • Maternal immune priming in oysters boosts offspring pathogen resistance. • Immunostimulants activate trained immunity, curbing OsHV-1 in aquaculture. • TGIP in bivalves offers cost-effective transgenerational disease control.