Frog hatchlings use early environmental cues to produce an anticipatory resource-use phenotype.

Developmental plasticity can occur at any life stage, but plasticity that acts early in development may give individuals a competitive edge later in life. Here, we asked if early (pre-feeding) exposure to a nutrient-rich resource impacts hatchling morphology in Mexican spadefoot toad tadpoles, Spea multiplicata . A distinctive carnivore morph can be induced when tadpoles eat live fairy shrimp. We investigated whether cues from shrimp--detected before individuals are capable of feeding--alter hatchling morphology such that individuals could potentially take advantage of this nutritious resource once they begin feeding. We found that hatchlings with early developmental exposure to shrimp were larger and had larger jaw muscles--traits that, at later stages, increase a tadpole's competitive ability for shrimp. These results suggest that early developmental stages can assess and respond to environmental cues by producing resource-use phenotypes appropriate for future conditions. Such anticipatory plasticity may be an important but understudied form of developmental plasticity.