Characterization of Epigenetic and Subcellular Responses to Desiccation/Heat-Stress Exposure in Diploid and Triploid Pacific Oysters

Triploid Pacific oyster (Crassostrea gigas) are an important economic source for the aquaculture industry. Triploid oysters can be marketed year-round because they do not undergo typical reproductive transformations. However, climate change has exposed oysters to new environmental stressors. The aquaculture industry has recently experienced high mortality rate among triploid oysters compared to diploid oysters which may be related to differences in stress responses. To better characterize the stress response in oysters, we assessed global DNA methylation and gene expression in triploid and diploid oysters following desiccation and heat stress. qPCR results indicated alterations in gene regulatory activity, immune response, and metabolic regulatory activity. Diploid oysters were hypermethylated following stress exposure suggesting an overall increase in gene regulatory activity. Triploid oysters had little change in global DNA methylation indicating a potential inability to incite specific epigenetic modifications in response to stress. Our findings elucidate the need to better characterize molecular and physiological stress responses in diploid and triploid oysters to understand the impact of climate change on the aquaculture industry.