Rapid epigenetic response to salinity stress in an invasive mussel, Mytilus galloprovincialis

The Mediterranean blue mussel (Mytilus galloprovincialis) is a well-known invasive species recognized for its remarkable ability to tolerate a wide range of environmental conditions. Here, we investigated DNA methylation changes in M. galloprovincialis exposed to a rapid water salinity decrease. Methylation profiles in M. galloprovincialis were recorded before salinity stress was applied (at 35‰), and then at 3, 9 and 24 h following the stress (at 25‰). We monitored these changes using the methylation-sensitive amplification polymorphism (MSAP) method. Methylation levels continued to vary over the 24 h period following stress exposure, indicating that the underlying physiological processes may have changed over time. There was a wide range of individual responses in hemimethylation and methylation at internal cytosine levels. In contrast, individual responses resulting from hypermethylation were more constrained, and the differentiation among progressive time groups was more pronounced. In invasive species, where a small group enters a new habitat, diverse individual epigenetic responses can compensate for the low genetic diversity by increasing phenotypic variations and broadening adaptation options. The rapid and diverse epigenetic responses of M. galloprovincialis to acute salinity stress suggest that epigenetic modifications may play an important role in rapid adaptation processes.