Role of Scavenger Receptors in Innate Immunity in Crustaceans.

Crustaceans are indispensable aquaculture species worldwide, and the scale of crustacean cultivation has been expanding continuously over recent years. However, pathogen infections have caused substantial economic losses in the global crustacean aquaculture industry. As invertebrates, crustaceans lack acquired immunity and entirely depend on innate immunity to resist pathogen invasion. Scavenger receptors (SRs) are an important type of pattern- recognition receptors (PRRs) in crustaceans that can specifically recognize pathogen-associated molecular patterns (PAMPs) and play a crucial role in innate immune responses. To provide a comprehensive overview of the literature regarding the roles of SR in crustacean immunological defenses, we first systematically summarized the classification (classes A-C) and structural-domain characteristics of SRs identified in various crustacean species. Second, we thoroughly elucidated the functional mechanisms involving SRs, including pathogen recognition mechanisms and downstream immune responses, such as phagocytosis, antimicrobial peptide (AMP) expression, apoptosis, and the pro phenoloxidase (proPO) system, that were triggered by different pathogens. Finally, we discussed SR-based disease prevention and control strategies, including selective breeding, immunostimulant development, and biomarker identification, with the aim of providing a theoretical foundation for elucidating immune mechanisms and advancing healthy crustacean aquaculture.