Caterpillars use developmental plasticity and diet choice to overcome the early life experience of nutritional imbalance

Nutritional conditions experienced during early growth have important implications for the lifetime fitness of herbivores in nutritionally heterogeneous environments. We investigated the early life effects of imbalanced nutrient intake on key fitness components and how such effects can be overcome in a generalist leaf-feeding lepidopteran caterpillar, Spodoptera litura. Over the fifth larval instar, caterpillars were pretreated on one of three diets that varied in protein and carbohydrate content (p35:c7, p21:c21 or p7:c35; % dry mass). After moulting to the sixth instar, they were transferred to one of three no-choice diets (p35:c7, p21:c21 or p7:c35) or a food choice where they received two nutritionally complementary diets (p35:c7 versus p7:c35). Approximately 80% of caterpillars that had been protein-deprived (p7:c35) during the fifth instar moulted to the seventh instar and developed into heavier pupae than those pupating after the sixth instar. The threshold body mass for pupal metamorphosis was 144 mg at the start of the sixth instar. Ingesting a diet low in protein or carbohydrate during the early instar led to a deficit in body protein or lipid content, respectively. When given a choice, caterpillars pretreated on the low-protein diet (p7:c35) selected significantly more protein and thus had a higher intake ratio of protein to carbohydrate than those from other diets (p35:c7, p21:c21). Our results suggest that caterpillars are not only capable of switching their developmental program to reduce the deleterious effects of an early deficiency of protein, but also flexible at adjusting nutrient preferences to redress specific nutritional imbalances experienced early in life.