Intergenerational Patterns of DNA Methylation in Procambarus clarkii Following Exposure to Genotoxicants: A Conjugation in Past Simple or Past Continuous?

Epigenome is susceptible to modulation by environmental pressures—namely, through alterations in global DNA methylation, impacting the organism condition and, ultimately, reverberating on the phenotype of the subsequent generations. Hence, an intergenerational study was conducted, aiming to clarify the influence of genotoxicants on global DNA methylation of the crayfish Procambarus clarkii. Two subsequent generations were exposed to the herbicide penoxsulam (Px; 23 µg·L−1) and to the genotoxicant model ethyl methanesulfonate (EMS; 5 mg·L−1). Px did not induce changes in DNA methylation of adult crayfish (F0). However, the hypomethylation occurring in unexposed F1 juveniles demonstrated that the history of exposure per se can modulate epigenome. In F1 descendants of the Px-exposed group, methylome (hypermethylated) was more affected in males than in females. EMS-induced hypomethylation in adult females (F0), also showed gender specificity. In addition, hypomethylation was also observed in the unexposed F1 crayfish, indicating an intergenerational epigenetic effect. The modulatory role of past exposure to penoxsulam or to EMS also showed a dependency on the crayfish developmental stage. Overall, this research revealed that indirect experiences (events occurring in a predecessor generation) can have an impact even greater than direct experiences (present events) on the epigenetic dynamics.