Meeting Abstract
Across animals, embryos can hatch in response to environmental cues. Early hatching can improve embryo survival when eggs are in danger, but may come at a cost to the larval life-stage. Thus, understanding the adaptive value of hatching plasticity requires evaluating the costs and benefits that characterize selective trade-offs. Several species of glassfrogs (Centrolenidae) can hatch as early as 7 days in response to predators, dehydration, and parental abandonment, or delay hatching to 20 days under good conditions. We measured two fitness correlates, for survival and growth, to test the adaptive value of delayed hatching in five species: Cochranella granulosa, Hyalinobatrachium fleischmanni, Hyalinobatrachium colymbiphyllum, Teratohyla pulverata, and Teratohyla spinosa. Hatchlings fall from arboreal eggs into streams and must dive to the bottom to escape predatory fish. We measured diving performance for early and late hatchlings to infer predation risk. As tadpoles cannot benefit from external food resources until they reach feeding competence, we quantified the onset of feeding and compared gut-coil development in siblings of different hatching ages. Older hatchlings dove faster and began feeding sooner after hatching than did younger individuals, suggesting that delayed hatching is advantageous for escaping predators and reducing lag-time in exotrophic-based growth of larva. However, early hatchlings began feeding at a younger age than did older hatchlings, at which point they had more developed gut-coils than their unhatched siblings, indicating that younger hatchlings accelerate development to feeding competence. This study provides insight on the selective trade-offs that favor hatching plasticity in glassfrogs.
