How Houdini tadpoles escape certain death

 Science Visualized Animals,Ecology How Houdini tadpoles escape certain death

Chemicals probably trigger a three-stage emergency early hatching process

By Helen Thompson 10:00am, July 28, 2016

RUN AWAY When predatory snakes take a bite out of clusters of unhatched red-eyed tree frog embryos, some manage to escape the slaughter by wriggling out of their eggs to safety.

Karen M. Warkentin

Magazine issue: Vol. 190, No. 3, August 6, 2016, p. 32

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Tree frog tadpoles are the ultimate escape artists. To avoid becoming breakfast, the embryos of red-eyed tree frogs (Agalychnis callidryas) prematurely hatch and wriggle away from a snake’s jaws in mere seconds, as seen at left. Embryos also use this maneuver to flee from flooding, deadly fungi, egg-eating wasps and other threats. Adding to the drama, red-eyed tree frogs lay their eggs on the undersides of leaves that hang a few inches to several feet above ponds. So the swimmers perform this feat suspended on a leaf, breaking free in midair and cannonballing into the water below.

High-speed video, captured by Kristina Cohen of Boston University and her colleagues, of unhatched eggs collected from Panamanian ponds shows that the embryos’ trick plays out in three stages. First, upon sensing a threat, an embryo starts shaking and gaping its mouth to stretch its egg membrane in the spot in front of its snout. Next, a hole forms. (The movement helps tear open the hole, but an embryo’s snout probably secretes a chemical that actually does the breaking.) Finally, the embryo thrashes its body about as if swimming and slips out of the egg.

Orientation is key to a hasty escape, the team reports in the June 15 Journal of Experimental Biology. An embryo must keep its snout aligned with the hole for a speedy exit. In observations of 62 embryos, the getaway took between six and 50 seconds — 20.6 seconds on average.

Some tadpoles may be leaping out of a cauldron into a fire. “There’s a trade-off,” Cohen says. “They may have escaped the threat of a snake, but earlier hatchlings fare worse against some aquatic predators.”

VOILA Watch embryonic escape artists in action. K. Warkentin, M. Caldwell, M. Seid, M. Hughey

Citations

K.L. Cohen et al. How embryos escape from danger: the mechanism of rapid, plastic hatching in red-eyed treefrogs. Journal of Experimental Biology. Vol. 219, June 15, 2016, p. 1875-1883. doi: 10.1242/jeb.139519.

Further Reading

S. Milius. Wasps drive frog eggs to (escape) hatch. Science News. Vol. 158, October 14, 2000, p. 246.

S. Milius. Smart from the start. Science News. Vol. 176, August 15, 2009, p. 26.

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How Houdini tadpoles escape certain death