How does parental diet affect offspring locomotor capacity in the bean bug, Riptortus pedestris?

Parental environments have profound consequences for offspring fitness through transgenerational transmission of resources and epigenetic factors. Locomotor activity is a functional trait of considerable ecological importance, as it determines the ability of animals to find food and mates and to disperse to more favourable environments. Although there have been studies demonstrating that animals can plastically increase their locomotor capacity in response to nutritionally stressful environments, it remains largely unexplored whether and how parental diet can adjust offspring locomotor capacity and its related traits. In this study, we tested the hypothesis that the parental intake of a nutritionally suboptimal diet would induce hyperactivity in the offspring and that this transgenerational effect could lead to improved offspring performance in an insect herbivore, the bean bug (Riptortus pedestris Fabricius) (Hemiptera: Alydidae). We compared the locomotor activity, metabolic phenotype and performance traits of two groups of R. pedestris nymphs born to parents raised on soybeans [Glycine max (L.) Merr, Fabaceae; standard diet] or peanuts (Arachis hypogaea L., Fabaceae; high-fat diet). Despite being smaller at birth, the offspring of peanut-fed parents moved faster and more frequently than those of soybean-fed parents during their early development. The newly hatched offspring born to peanut-fed parents had higher relative energy reserves in somatic tissues than those born to soybean-fed parents, indicating that differential parental provisioning could underpin this parental effect on offspring locomotor activity. Possibly through increased foraging activity, the hyperactive offspring of peanut-fed parents grew faster into heavier adults than the offspring of soybean-fed parents, implying that parentally induced increase in offspring locomotor activity is adaptive. This study provides experimental evidence for diet-mediated transgenerational plasticity of locomotor activity in invertebrates and sheds novel insights into the role of parental diet history in shaping offspring phenotype.