Unborn embryos of tree frogs hatch prematurely to evade mortal peril: mechanism of rapid escape unveiled


When confronted with imminent danger, the red-eyed tree frog embryos use both physical force and enzymatic action to quickly wriggle out of the eggs even before (up to two days ahead) they are fully developed.


Researchers at the Smithsonian Tropical Research Institute (STRI) in Panama have uncovered the secret behind the premature release of red-eyed tree frog embryos upon sensing risks. Further, their results disclose exciting information that the embryos are able to assess the level of risk, distinguish between malicious and benign interventions, make decisions, and employ survival strategies (physical and chemical).

The study was originally published in the Journal of Experimental Biology.

Found as jelly masses on leaves, these eggs are prone to life threats such as predator attacks and environmental changes (floods may cause them to fall into a water body that is hypoxic).

“Most people think of embryos as fairly passive,” said Karen Warkentin, STRI research associate and professor at Boston University. “But evidence keeps accumulating that embryos of many species are actively engaged with their world, not only receiving information but also using it to do things that help them survive.” She explains the experimental approach and the adaptive behaviour of tree frogs here.

Mimicking the two different scenarios (predator attack and heavy rains) at the laboratory through vibrations, Kristina Cohen, the lead author of this study, observed the eggs closely using high-speed videos. The escape hatch was reported to take between six and 50 seconds, with an average of 20 seconds for the premature tadpoles to drop from their cluster.

Besides the embryos lashing around inside the egg (physical force), the scientists also observed a liquid being released near their mouths. Only post this event, they pushed their snouts through the membrane and squeezed out. Further examination of the snouts under the electron microscope revealed clusters of glands that were filled in unhatched embryos and empty in new hatchlings.

“The process of getting out of the egg is the embryo’s first, tiny, athletic event,” Warkentin said.

This suggests that survival strategies are not limited to the young and adult frogs. These investigators intend to understand the rapid responses in animals by studying how the embryos coordinated both the secretion of the enzyme and the body movements. Given the number of species that are similarly vulnerable in the wild, many such mechanisms remain undiscovered.

Watch details of the mechanism in this video.

Sources: Science daily, Science