Meeting Abstract
Hatching early allows embryos to escape threats to eggs, but increases risks to larvae. Red-eyed treefrogs hatch by rapidly releasing enzymes to digest a small hole in their membrane, then squeezing out aided by turgor pressure. Displacement from the initial hole can occur spontaneously and in predator attacks, complicating hatching by capsular collapse as fluid escapes. To assess developmental changes in ability to recover from such complications, we manually displaced 3–5 day old embryos during hatching, interrupting exit through their initial hole, and recorded macro-video. To induce hatching of younger, vibration-insensitive embryos, we submerged individual eggs in hypoxic water. For older embryos, we used a blunt probe to jiggle eggs within clutches. Once an embryo began hatching, we manually displaced it, moving its snout away from the forming or just-formed hole. We analyzed videos to assess if and how embryos escaped. The least-developed embryos rarely escaped from collapsed capsules but performance improved rapidly; late stages always escaped. Embryos escaped by either re-finding their first hole or making a second. The post-displacement delay to start an exit through the first hole was similar across stages. Even at the earliest stages, a few individuals made second holes, but the likelihood of doing so increased rapidly, to about 75%. More developed embryos spent less effort searching for their first hole; they made second holes sooner and more efficiently. They also passed through the membrane more rapidly, with less body compression in transit. Along with high risk after hatching, poor ability to escape from hatching complications may select against unnecessary hatching attempts at early developmental stages.
