From stress to response: a systematic review of epigenetic pathways underlying gene expression and phenotypic plasticity in aquatic invertebrates

Marine and freshwater ecosystems are undergoing rapid transformations propelled by human activity, placing unprecedented pressure on aquatic species and threatening critical ecosystem services. Aquatic invertebrates, which underpin aquaculture industries, shape habitat structure, and contribute to biomedical discovery, are particularly vulnerable, yet their capacity to respond to environmental change remains understudied. Epigenetic mechanisms have emerged as potential mediators of rapid acclimatization, but their roles in aquatic invertebrates are not well defined. In this review, we systematically analyzed 223 studies that examined epigenetic responses of aquatic invertebrates to environmental or anthropogenic stress. For each study, we recorded taxonomic representation, stressor type, exposure duration, experimental design, and major molecular and phenotypic outcomes. DNA methylation was the most frequently investigated mechanism, mollusks were the dominant study phylum, and infection was the most common stressor; however, substantial variation and ongoing debate were evident across molecular findings. Epigenetic processes are increasingly recognized as key regulators of gene expression and phenotypic plasticity, yet their functional significance, temporal stability, and heritability in aquatic invertebrates remain uncertain. By synthesizing existing evidence and compiling a comprehensive database of current research, this review establishes a foundation for advancing environmental epigenetics toward a predictive, mechanistic framework capable of informing conservation, aquaculture, and ecosystem management under accelerating global change.