Spotlight
Research: Toad Tongues
| USF News
Photo courtesy of Stephen Deban
Biologists have known for decades that toads snare prey by flipping their sticky tongues in just a few thousandths of a second. More recently, researchers determined that the notoriously slow toad springs its mouth open using elastic recoil in a bow-and-arrow mechanism that literally whips out its tongue and catches its prey.
Now, scientists have learned that toads have another trick — they can flip their tongues and feed even in the cold, at temperatures that virtually immobilize many amphibians and reptiles.
In a recently published study in the Journal of Experimental Biology, Stephen Deban, assistant professor in USF's Department of Integrative Biology, and Kristopher Lappin of California State University Pomona, concluded it is the elastic recoil mechanism itself that gives toads their cold-proof tongue flipping ability.
Deban and Lappin knew that muscle contractions are severely slowed by cold temperatures, and that ectotherms, like amphibians and reptiles, can't warm their bodies above the temperature of their surroundings. The researchers reasoned that the toad's elastic recoil mechanism should allow them to circumvent this limitation — "like shooting a bow and arrow," Deban says.
"It doesn't matter how long it takes the muscles to draw back the bow, the arrow always flies at the same speed," he adds.
To test their hypothesis, Deban and Lappin used high-speed digital imaging to capture the details of southern toads, Bufo terrestris, feeding on crickets and beetles. They simultaneously made electromyographic recordings of the mouth opening and closing muscles, to determine when the muscles were activated by the nervous system.
The high-speed images revealed just what Deban and Lappin predicted: the toads launched their tongues with nearly the same speed at all temperatures. Feeding movements that are not elastically powered, however, were strongly affected by cold.
Last year, Deban's laboratory discovered that chameleons can shoot their tongues out with maximum performance whether they are cold or warm, also by virtue of an elastic mechanism.
"Finding the same phenomenon in toads, which have evolved their tongue projection independently from chameleons," Deban says, "suggests that elastic mechanisms may be a widespread strategy among animals to maintain high performance in the cold."