Frog Vomiting Is the Darndest Thing
The human emetic response -- more commonly known as hurling, puking, ralphing, upchucking, or vomiting -- is a fairly simple process. In the retching phase, the abdominal muscles and the diaphragm begin a series of coordinated contractions similar to hiccupping. Essentially, the muscles are warming themselves up for the second and final phase of human vomiting: expulsion. Here, the abdominals and the diaphragm contract again, but this time they hold in a tightened position for an extended period of time, forcing anything inside the stomach back towards the hole from whence it came. Before exiting the body, gastric contents are halted at a gatekeeper of sorts: the esophageal sphincter. At the sphincter, tremendous pressure builds -- imagine squeezing a capped tube of toothpaste. After a few moments, the cap is opened, and everything comes exploding out, hopefully not all over anybody else.
If that process sounds in any way nauseating, or heck, even exciting, just wait till you see what frogs do!
Anything in particular catch your attention? For those who didn't watch, a toffee-colored bulbous organ jetted out of our poor friend's mouth. One might assume that to be his tongue. Nope. That was his stomach -- turned inside out -- which our amphibian friend then wiped clean with outstretched forelegs, and swallowed back up. Go big or go home: that's how frogs do it.
Of course, not all frog species literally puke their guts out. Rana – whose members include the American bullfrog – and Xenopus – African Clawed frogs – are the two genera commonly known to do so. Each has their own unique style, as Dalhousie University biologists Tomio Naitoh, Richard Wassersug, and Ronald Leslie discovered, and artfully diagramed, in pioneering research published in 1989.
Notice that the frogs' stomachs weren't shown hanging out in the illustrations. That's because the amphibians don't always upchuck their stomachs. The action is really more of a drastic measure, for when the frogs eat something particularly nasty and must be thorough in removing it. Poisonous insects are common culprits.
Frog vomiting is of interest to scientists for more than just quirks. As one of the most basic organisms to have evolved emesis, they may help us understand the processes that cause vomiting in humans. In 2000, Wassersug and Naitoh sent frogs into space to fundamentally examine motion sickness. As it turns out, frogs get nauseous in zero gravity, too.
(Image: Frog via Shutterstock)