Transgenerational cross-tolerance to stress: parental exposure to predators increases offspring contaminant tolerance.

Transgenerational effects of stressors can have important implications for offspring fitness and the responses of offspring to future stressful conditions. Parental effects, a common type of transgenerational effect, are non-genetic influences on offspring phenotype that result from parental phenotypes or environments. Little is known, however, about how parental exposure to a stressor effects offspring responses to other stressors despite this type of multi-stressor scenario being common. To better understand the role that parental effects have on offspring contaminant tolerance, we raised freshwater snails, Biomphalaria glabrata, in the presence or absence of predator threat (crayfish + crushed snail) for 12 weeks. Predators are common stressors in aquatic systems and can co-occur with chemical contaminants. We then collected egg masses from parental snails and exposed their offspring to cadmium and malathion survival challenges. Snails raised in the presence of predator threat displayed indicators of stress, including increased time to first reproduction, lower production of egg masses per snail per day and fewer eggs per egg mass, and had smaller shell lengths at 6.5 weeks old compared to snails not exposed to predator threat. Parental exposure to predator threat increased the cadmium tolerance of offspring but did not affect malathion tolerance. These results may have important implications for understanding effects of multiple stressors and indicate that the parental environment can influence responses to contaminants in offspring. To our knowledge, this is the first study to demonstrate that a biotic stressor in the parental environment can significantly affect the contaminant tolerance of their offspring.