Abstract
Aquaculture of molluscs and crustaceans represents an important and expanding sector within global food production. The intensification of these systems has been accompanied by an increased prevalence and severity of infectious diseases, which continue to constrain productivity and sustainability. Current disease management approaches include biosecurity measures, husbandry practices, therapeutics, and selective breeding, which have shown limited efficacy against many emerging pathogens affecting invertebrate species. Unlike finfish, aquatic invertebrates lack adaptive immunity and rely exclusively on innate immune mechanisms, limiting the effectiveness of traditional vaccine strategies. There is growing interest in immunostimulants that enhance innate defenses and support immune priming or trans-generational immune priming (TGIP). This review summarises the current understanding of immune defence mechanisms in molluscs and crustaceans and examines recent progress in the development of immunomodulators and prophylactic interventions aimed at improving health outcomes and disease resilience in invertebrate aquaculture.