You may already know that slugs and snails have thousands of tiny teeth, all lined up in circular jaws.
But you might not be aware that some frogs have them too.
Yup ― it’s not uncommon for certain species to have tittle gnashers on their upper jaw, though only one species has been known to have both a top and bottom set.
Many are toothless too.
According to the Florida Museum, “Some have tiny teeth on their upper jaws and the roof of their mouths while others sport fanglike structures.”
However even the most uncomplicated of frog teeth have a strange relationship to the species: “Scientists have long known that frogs are oddballs when it comes to teeth.”
Why do they have teeth, and why does it change so much?
The Florida Museum of Natural History found that frogs lost and regained teeth over 20 times in their evolution.
That’s more than any other vertebrates (animals with spines).
“Only eight other groups of living vertebrates, including seahorses, turtles, birds and a few mammals, have also evolved toothlessness,” Daniel Paluh, a Ph.D. candidate in the University of Florida’s Department of Biology, told the museum.
It seems to have to do with their diet ― “Having those teeth on the jaw to capture and hold on to prey becomes less important because they’re eating really small invertebrates that they can just bring into their mouth with their highly modified tongue,” Dr Paluh said.
“That seems to relax the selective pressures that are maintaining teeth.”
However, Nat Geo points out that some frogs like South America’s Pacman frog have a diet that should require teeth; but their gnashers are actually fake.
Frogs aren’t alone
If it sounds strange to lose, re-grow, and then lose teeth again, I would agree ― but we have to remember, nature is nothing if not odd.
Some species of limpet have grown, then lost, then regained a coil pattern in their shell. Certain lizard species have acquired, lost, and brought back the ability to lay eggs.
This, along with frog teeth, contravenes an evolutionary rule called Dollo’s Law of Irreversibility, which suggests that once a species has lost a trait, it’s gone forever.