Parental immune priming reshapes offspring growth, metabolism, and thermal tolerance in the Pacific Oyster

Pacific Oysters (Magallana/Crassostrea gigas) are marine bivalves that are widely cultivated but increasingly experience summer mortality due to interacting stressors. Two major concerns are (1) the rising severity and frequency of marine heat waves and (2) disease outbreaks (e.g., OsHV-1). To better understand how multiple stressors influence oyster resilience and whether stress priming can improve survival, we tested the effects of parental immune challenge on offspring performance. We exposed broodstock to a Poly(I:C) immune challenge, reared their offspring to the seed stage, and assessed survival, growth, and metabolic responses under thermal stress in the lab. Offspring of immune-challenged parents showed higher growth rates during development. Under elevated temperatures, these offspring had higher survival than controls at 40{degrees}C, but lower survival at 42{degrees}C, suggesting thermal limits to priming benefits. Metabolic assays further revealed that at moderately elevated temperature (36{degrees}C), primed offspring had higher metabolic activity, whereas at higher temperature (40{degrees}C), they exhibited lower metabolic activity than controls. This pattern indicates that parental immune challenge may influence offspring metabolic flexibility, potentially enhancing thermal tolerance through an increased capacity for metabolic depression at extreme temperatures. Together, our results highlight cross-generational links between immune priming and thermal tolerance.