Evolutionary diversification and expressional profile of adrenergic receptors in the Pacific oyster Crassostrea gigas

Collectively, these results suggested that the retention of Cgα2Da/α2Db-AR subtypes in oysters under relaxed selection pressure reflects an evolutionary strategy for immune adaptability. Their lineage-restricted diversification drives differential expression (e.g., Cgα2Da-AR in granulocytes) and post-challenge resilience (e.g., Cgα2A-AR upregulation), balancing energy conservation and pathogen defense. These findings provided a foundation for further elucidation of their immunoregulatory roles in oysters and contribute to an improved understanding of AR evolution in invertebrates.