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

Abstract

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.

Keywords: Spea multiplicata; anticipatory plasticity; developmental plasticity.

Figure 1.

Developmental plasticity in spadefoot toad tadpoles. (a) Spea multiplicata develop into an omnivore or carnivore morph, which has features (e.g. large jaw muscles) for eating animal prey, such as fairy shrimp. (b) Previous studies have shown that carnivores are produced when young omnivores eat shrimp. (c) We investigated whether early (pre-feeding) exposure to shrimp caused hatchlings to produce more carnivore-like features (note the hatchling (yellow arrow) surrounded by embryos; hatchlings remain immobile and do not feed for 24 h after hatching).

Figure 2.

Response variables of S. multiplicata hatchlings that developed in shrimp nauplii's absence (blue dots) or presence (orange dots). Measurements of snout–vent length (SVL) (a), Gosner developmental stage (b), average width of the orbitohyoideus (jaw) muscle standardized by SVL (c) and gut length standardized by SVL (d). All panels show the individual data points (dots), where the width of the jitter represents the density distribution (mean ± s.e.m. are shown in black font). Traits in bold font represent significantly different groups (p < 0.05).