Ocean warming and acidification reveal transcriptional plasticity in the gastropod Hexaplex trunculus.

Coastal ecosystems, particularly in the rapidly warming Mediterranean Sea, are increasingly impacted by climate change driven by ocean warming and acidification. Calcifying marine invertebrates are especially vulnerable, yet their molecular responses remain poorly understood. Gene expression dynamics in the ecologically and commercially important gastropod Hexaplex trunculus were investigated under simulated scenarios combining elevated temperature and reduced pH. High-throughput RNA sequencing was used to generate a de novo assembly of the foot transcriptome, followed by differential gene expression analyses to characterize molecular responses to individual and interactive stressors under high-emission (RCP 8.5) projections. The foot tissue - central to locomotion, adhesion, and environmental interaction - exhibited pronounced transcriptional changes in genes associated with calcium signaling, ion transport, aerobic respiration, muscle contraction, and transmembrane transport. Ocean acidification emerged as the dominant driver of transcriptional change, inducing substantial shifts in metabolic demand and ion regulatory pathways, which might suggest increased energetic costs and potential functional constraints. The results demonstrate marked transcriptional plasticity in H. trunculus under combined climate stressors. By providing foundational transcriptomic resources for this species and mechanistic insight into its response to projected environmental changes, this study advances the understanding of molecular processes in vulnerable Mediterranean gastropods and informs ecological assessment efforts in rapidly warming marine ecosystems.