Until now, it was not known what happened when frogs placed prey inside their mouths with the help of their sticky tongue, now it can be seen in 3D
Swallowing a toad must be very unpleasant, but it seems that for toads, specifically cane toads (rinella marina), swallowing one’s own tongue is an everyday thing. The authors of one study used X-ray videography to study the feeding behavior of frogs, providing the first 3D view of what frogs do with food when it’s held in their mouths. They are aided by a complex system of cartilage and muscle pulleys that extend across the throat and reach nearly the height of the heart.
“We know a lot about how frogs extend their tongues and how they attach to their prey, but prior to this study, basically everything that happens after frogs close their mouths was a mystery,” said lead author Rachel Keeffe, who completed the study. study. at the Department of Biology at the University of Florida🇧🇷
As early as 1827, naturalists were fascinated by the eating habits of amphibians. But frogs are extremely quick at catching and consuming their prey, so much so that the human eye finds it nearly impossible to track their movements. It wasn’t until the development of high-speed video in the mid-20th century that scientists were able to directly observe how frogs’ tongues unfold like an explosion and engulf their hapless targets in a gooey embrace.
Even then, scientists could only guess at how they swallowed their food. Some have theorized that frogs used their tongues to deposit food directly down their throats, while others have suggested that they pushed food away by squinting. But none of these early ideas could explain the strange structures the researchers found inside the frogs’ mouths during dissections.
The curious mouth of the frog
Many frog species have two sets of fang-like teeth on the palate, and toothless frogs have ridges along the upper palate that resemble a washboard. Amphibians also have a cartilaginous plate called the hyoid, which has loops and spikes attached to the muscles and which Keeffe compares to a puppet. The hyoid plate rests on the floor of the mouth, and its function in relation to frogs’ ability to swallow prey was completely unknown.
To find out how the frogs handle their food, Keeffe and his colleagues placed metal beads at key points in the cane toads’ mouths. rinella marina🇧🇷 Cane toads, which can measure up to 15 centimeters, are one of the largest frog species, making them the perfect specimen to observe the quick and tiny movements they make when eating.
After placing the frogs in a transparent viewing box, Keeffe fed them a steady stream of crickets while filming them with X-ray videography. An initial examination of the resulting videos revealed a different mechanism than they expected. “At first, we weren’t sure what was going on,” Keeffe said. “The entire floor of the mouth was dragged back into the throat and the tongue with it.”
Keeffe spent months painstakingly reconstructing the movements in 3D animations to determine exactly how the device worked. He then illustrated accurate gameplay from the frames, starting with the moment each cricket is selected and rolled in the mouth.
When the tongue reaches its maximum extension, the hyoid is retracted towards the throat. The tongue, which is directly attached to the hyoid, again enters the mouth. It’s not clear how far the hyoid can retract because its path is blocked by the frog’s heart, which it slides against for milliseconds before the tongue and prey fang slam into the cartilaginous pad, Keeffe explained.
Although the frog managed to capture its prey at this point, it still faces the problem of having to pluck the hatched insect from its sticky tongue. It does this in the last stage of feeding, which the authors call hyoid dorsal ascension. “The hyoid rises and presses the tongue against the roof of the mouth, after which it moves forward, essentially scraping food down the esophagus.”
The final climbing and scraping movement may explain the presence of grooves and fangs on the upper palate of some frogs, Keeffe said. “If this is what all frogs do, then these structures definitely play a role in swallowing.”
The entire process, from start to finish, takes less than two seconds, with most of the time spent repositioning the tongue and hyoid bone after swallowing.
There is an incredible diversity of feeding mechanisms among the 7,000 known species of frogs, ranging from the projectile tongues of toads to the suction feeding of aquatic frogs. Keeffe says the obvious next step would be a cross-species study to see if the cane toad’s feeding behavior is the rule rather than the exception.
REFERENCE
XROMM Analysis of Feeding Mechanics in Frogs: Tongue, Hyoid, and Pectoral Girdle Interactions