As the frog embryos grew, tiny parts came into view. Biology graduate student Estefany Caroline Guevara-Molina watched them develop at the Smithsonian

When the Heat is On, Red-Eyed Treefrogs Hatch Early

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2022-10-02 12:30:22

As the frog embryos grew, tiny parts came into view. Biology graduate student Estefany Caroline Guevara-Molina watched them develop at the Smithsonian Tropical Research Institute (STRI) in Panama. On day two, small hearts began blinking like signals beneath translucent chests. On day three, eyes blackened and swaying sets of external gills lengthened in branches. On day five, sensory systems like the vestibular system and its inner ear organs were in place to detect the strike of a snake, the bite of a wasp, or the creep of fungus over the eggs. That’s when Guevara-Molina exposed the eggs to heat. In droves, the embryos hatched before they were due.

This behavior makes red-eyed treefrogs the first species whose embryos are shown to hatch to escape overheating, and it adds rising temperature to the frogs’ known triggers of early hatching, including vibrations made by predation and oxygen loss in flooding.

Guevara-Molina reported the finding alongside Boston University biologist Karen Warkentin, who conducts research at STRI, and physiologist Fernando Ribeiro Gomes of the University of São Paulo in a study published in Integrative Organismal Biology this week. “The more questions we ask of them, the more we find out about what [the frogs] can do,” says Warkentin, who led the research team. “The fact that the embryos have a behavioral response to thermal stress, which gets them out of the egg and into the presumably cooler pond, is really interesting because it opens a bunch of other questions.”