Transgenerational plasticity and the capacity to adapt to low salinity in the eastern oyster, Crassostrea virginica

Abstract

Salinity conditions in oyster breeding grounds in the Gulf of Mexico are expected to drastically change due to increased precipitation from climate change and anthropogenic changes to local hydrology. We determined the capacity of the eastern oyster, Crassostrea virginica , to adapt via standing genetic variation or acclimate through transgenerational plasticity (TGP). We outplanted oysters to either a low- or medium-salinity site in Louisiana for 2 years. We then crossed adult parents using a North Carolina II breeding design, and measured body size and survival of larvae 5 dpf raised under low or ambient salinity. We found that TGP is unlikely to significantly contribute to low-salinity tolerance since we did not observe increased growth or survival in offspring reared in low salinity when their parents were also acclimated at a low-salinity site. However, we detected genetic variation for body size, with an estimated heritability of 0.68 ± 0.25 (95% CI). This suggests there is ample genetic variation for this trait to evolve, and that evolutionary adaptation is a possible mechanism through which oysters will persist with future declines in salinity. The results of this experiment provide valuable insights into successfully breeding low-salinity tolerance in this commercially important species.

Evolution in changing seas

“…Low salinity conditions resulted in slower growth and reduced body size at metamorphosis, which was associated with mortality at later stages [26]. While they did not find evidence of strong transgenerational plasticity, they did find high heritability for body size under low salinity conditions, suggesting that there is ample genetic variation for this trait to evolve in response to declining salinity in the future [26].…”

“…Griffiths et al teased apart the roles of standing genetic variation and transgenerational plasticity in low salinity tolerance of the Eastern oysters in the Gulf of Mexico, which is predicted to experience declining salinities under climate change. Low salinity conditions resulted in slower growth and reduced body size at metamorphosis, which was associated with mortality at later stages [26]. While they did not find evidence of strong transgenerational plasticity, they did find high heritability for body size under low salinity conditions, suggesting that there is ample genetic variation for this trait to evolve in response to declining salinity in the future [26].…”

Differential DNA methylation across environments has no effect on gene expression in the eastern oyster

“…The role of methylation in environmental responses of oysters is of particular interest because this species faces a rapidly changing environment, and epigenetic methylation is a possible mechanism for transgenerational inheritance of environmentally responsive phenotypes. Our previous work with C. virginica provides evidence both for environmentally induced methylation differences and for transgenerational inheritance in oysters, with parental acclimation to sites with differing salinity conditions contributing to variation in larval traits (Griffiths et al, 2021).…”

“…Our previous work with C . virginica provides evidence both for environmentally induced methylation differences (Johnson & Kelly, 2020) and for transgenerational inheritance in oysters, with parental acclimation to sites with differing salinity conditions contributing to variation in larval traits (Griffiths et al., 2021).…”

Divergence in salinity tolerance of northern Gulf of Mexico eastern oysters under field and laboratory exposure

“…It has been shown that epigenetic divergence exceeds genetic divergence in some Louisiana oyster populations ( Johnson and Kelly, 2020 ). However, another study found no evidence for parental carryover effects on larval tolerance of low-salinity conditions, even after parental stocks were maintained at low-salinity conditions for 2 years ( Griffiths et al, 2021 ). While our studies were limited to characterizing the performance of the progeny of wild oysters (i.e.…”