Special spit helps frogs get a grip on insects
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Let’s just get this out of the way: Frogs are cool. They jump. They thrive in water and on land. And their tongues are capable of sticking to bugs like glue. This is true even of insects that are heavier than they are. And now, the mysteries behind those incredible tongues are being revealed. The secret sauce that makes frog tongues so deadly to insects turns out to be a simple one. Their spit. That's according Ben Guarino reporting for The Washington Post.
A new study reveals that frog saliva is more fascinating than previously thought. It was published in the Journal of the Royal Society Interface. Tests showed that it’s both uniquely sticky and physically astonishing. It can actually change physical properties.
For the study, researchers examined frog saliva. They studied it in combination with the frog’s soft and elastic tongue. Fluid tests of the spit showed that it’s a non-Newtonian fluid - it has properties different from normal liquids.
Your average Newtonian fluid (as described by Sir Isaac Newton) has the same properties as other such fluids. They freeze at the same temperatures and move into containers in the same ways. They flow with the same characteristics.
But then there are the non-Newtonian fluids—liquids that seem to have a mind of their own. Among their ranks are ketchup and melted chocolate Lava is also included in this group. And apparently frog saliva. These fluids take on different properties at different times. And they don’t behave the same way. (Just think of how the face of a cliff can turn to water during the sudden movement of an earthquake.)
When they studied the non-Newtonian frog spit, researchers learned that it's reversible. That's right. It can change from a glue-like substance into a very thin fluid and back again.
But the tongue's important, too. Researchers studied frozen frog tongues and found that they are ten times softer than the human tongue. They learned that, when combined with the non-Newtonian spit, the uniquely soft tongues have two functions.
The thin spit is still 50,000 times more viscous than human saliva and helps the tongue hit and release from bugs. The tongue deforms and its contact area becomes bigger. This happens when it hits a bug. The force of this impact against the bug turns the spit into a thin liquid, allowing it to ooze around its prey. But then the tongue retracts and the saliva thickens. It sticks to the bug and makes it easier to get the critter into its mouth.
What’s the point of studying frog spit? Why did they press on frog tongues and videotape eating frogs? Researchers tell Guarino that the research could one day inspire new, resealable adhesives. The future could very well contain Post-its or envelopes with frog spit-inspired glues—or devices that capitalize on the frogs’ unique ability to grab bugs. Until then, the amazement of the little amphibians make it well worth trying to figure out what makes their tongues tick.