By the time the pumpkin toad blows up, anything seems possible. The little frog, the size of a bee and the color of a cloud, has no problem jumping high above the ground. But when the pumpkin toad starts to fly, something goes wrong.
The frog’s body, with its limbs open like a starfish, begins to spin. And then he falls, tumbling gracefully until he lands on his back or head and unwittingly turns or turns back until he stops.
“Some guys are spinning,” said André Confetti, a graduate student at the Federal University of Paraná in Brazil, who was shown spinning his finger in the air during a Zoom call. “Some guys make that move,” Confetti added, moving his fingers in circles like a ferris wheel.
“Frogs flutter in the air, in space,” said Amber Singh, who will soon be a master’s student at San Jose State University.
The pumpkin toad, which is a frog but not a toad, is so terrible at landing its jumps that its sheer incompetence has become a subject of scientific research. A team of researchers from the United States and Brazil, including Confetti and Singh, say they have an answer: Miniaturized toads are so small that the fluid-filled chambers in their inner ears that control their balance work rather ineffectively. , condemning the brave jumpers. to a lifetime of accidental landings.
The article confirms that many species of pumpkin toads, which belong to a genus of tiny frogs called Brachycephalus, exhibit “a very unusual leap with uncontrolled landing behavior,” said Thais Condez, a researcher at Carleton University in Canada, which was not involved with the investigation.
Or, as Confetti put it, “they don’t do anything right.”
It is not easy to be a vertebrate the size of a bee. Pumpkin toads have made evolutionary compensations so small, such as reducing the number of digits on their legs from five to three. Frogs, which are famously wet, dry faster when they become so small, said Rick Essner, a functional morphologist at the University of Edwardsville in Southern Illinois and author of the paper. But sometimes it pays to be small: “For a pumpkin toad, an ant is a huge food,” Essner said.
Credit: André ConfettiPumpkin toad, Brachycephalus coloratus.
Frogs developed the ability to jump rather than land, meaning not all frogs have mastered the second part of the process. Essner previously investigated a group of equally clumsy-tailed frogs, which jumped acceptable enough but landed with a full-face plant.
When Marcio Pie, then a researcher at the Federal University of Paraná in Brazil and author of the paper, learned of Essner’s research on the frog, he emailed Essner about pumpkin toads. Members of Pie’s lab began collecting toads and other miniaturized frogs from nature to watch them jump and (attempt) to land.
Pumpkin toads live elusive lives. Frogs live and feed under fallen leaves in the Atlantic forest of Brazil, which, combined with their size, makes them very difficult to study. “They’re very small, secretive organisms,” Condez said. “Most of our knowledge of their behavior comes from rare observations in the field.”
Finding frog-sized frogs in Brazil is a daunting task. Although a pumpkin toad is as bright as a Cheeto, the leaf litter is full of neon fungi and other orange life forms. “It’s extremely difficult to catch under the leaf litter,” Confetti said. “Especially for me, because I’m colorblind.”
Instead, the researchers had to listen to the call of the frog, which sounds a bit like a grill. Back at Pie’s lab, the researchers placed each frog in a mirror surrounded by barriers and filmed their jumping efforts. (Some had to cheer with a soft touch on their little back.)
When Essner saw the footage, he burst out laughing. It was then immediately consumed by the problem in question. The toads were so far away from the tailed frogs that they sank the belly of the frog’s family tree, which means the problem was not ancestral. So why couldn’t they make a single leap? “It wasn’t a ‘Eureka’ moment,” Essner said. “It was, ‘What the hell is going on here?’ moment. ”
Credit: Rick EssnerBrachycephalus coloratus does his best.
Essner proceeded to read a large number of scientific articles, including a previous experiment in which researchers damaged the vestibular systems of reed toads, which are usually excellent hoppers. The compromised toads had landing problems strangely similar to pumpkin toads.
Essner wondered if the toad problem was reduced in size. Vertebrate organisms are able to balance us and orient us in the world thanks to our vestibular system: a complex system of chambers and channels full of fluid in our inner ear. Moving the head causes the fluid, called the endolymph, to produce a force that deflects the sensory hair cells and tells our central nervous system to control our posture and movement. Despite the huge body size range of vertebrates, the size of these channels is still quite consistent. “Between a bull frog versus a human or a whale, they don’t change as much as you might expect,” Essner said.
The researchers suspected that the toad’s small body and smaller skull may be restricting the size of the semicircular canals of its inner ear and preventing the inner fluid from flowing freely. “When you take a tube and make it smaller and smaller, that resistance to fluid flow increases,” Essner said.
David Blackburn, curator of herpetology at the Florida Museum of Natural History, and Edward Stanley, an associate scientist at the museum, performed CT scans of museum specimens of 147 species of frogs, including the largest frog (the Goliath frog). ), the smallest frog. (“There are a couple of ongoing frog species for the smaller frog,” Stanley noted) and the pumpkin toads. The frogs were kept in a “standard frog position, fairly stiff and not super floppy,” as Stanley described it. He packed the preserved frogs in Ziploc bags of peanuts and scanned them with the $ 1 million machine. Singh then depicted 3D models of the semicircular channels of frogs from CT scans.
The resulting measurements revealed that the semicircular canals of Brachycephalus and the miniature frogs of Paedophryne were the smallest of all adult vertebrates, resulting in a loss of motor control and subsequent chaotic landings.
The researchers considered other potential explanations. Maybe the three-toed feet of the pumpkin toads slipped during the initial jump? Or maybe their ridge landings were meant to look like a falling leaf, tricking predators into looking for a snack? But the videos did not show a significant amount of slip on the toads taking off, and the landed toads did not stand still long enough to convincingly resemble a leaf, the researchers wrote.
CT scans also hinted that toads may have evolved some internal bone armor to make it a little safer to crash. “They look like they’re carrying a backpack that’s all bone,” Stanley said, referring to the pumpkin toad species Brachycephalus ephippium. Still, the pumpkin toad is more likely to be a trundler than a jumper. Essner suggested that jumping is probably a getaway response, a way to rush away from a dangerous situation. Better a poor horse than no horse at all. Also, “you don’t have to worry about breaking bones if you’re the size of a housefly,” Essner added.
Pumpkin toads live in the Atlantic forest of Brazil, which is one of the most biologically diverse places on the planet. “Every mountain in southern Brazil has the potential to have a new species of Brachycephalus,” Confetti said. “We don’t know how many Brachycephalus we have in the backyard.”
But 85 percent of the region has been deforested and the rest is heavily fragmented. “It makes me wonder how many of these species there were that we’ll never know, because they’re already extinct,” Essner said.
Maybe the take-away thing about pumpkin toads is that not everything has to be optimized. Being bad at something doesn’t mean you shouldn’t, especially if you have a secret bone backpack and toxic glands. Even if the small jump of the pumpkin toad is the locomotive equivalent of the horse’s drawing, this does not mean that it does not have to walk, jump or fall as it pleases, among the damp leaves of a disappearing forest. All species should have the right to fail dramatically, but on their own terms.
Credit: Rick Essner Brachycephalus brunneus made the effort.