Close to the forest floor in the mountains of Brazil, a tiny spot of neon orange makes a soft, cricket-like chirp. This male pumpkin toadlet — a frog only about the size of the tip of an adult human’s finger — is hoping to find love.
But it had better not rely on its conversational skills. Both the males and females are deaf to their own calls, a new study shows. Instead, the throat swellings that accompany their chirps might be what catches a lady’s’ eye. The soft calls themselves may simply be leftovers from a long ago ancestor — and an example of evolution in action.In many species of frogs, males grab the attention of would-be mates with a serenade. But frogs don’t have visible outer ears, as humans do. Instead, “there’s a disc behind the eye,” notes Sandra Goutte. She works at the University of Campinas in Brazil. As a herpetologist, she studies reptiles and amphibians. That disc, she notes, is the tympanum, or ear drum, of its middle ear. Sound waves hit the frog’s ear drum directly and get transmitted to the inner ear. This membrane helps to increase the amount of sound energy transmitted to the inner ear.
In that inner ear, tiny hair cells are arrayed in organized ranks. They aren’t real hairs. These just resemble them as they bend and sway in response to sound waves. Their movement transmits sound signals to the brain. In people, high frequency sounds — such as the pumpkin toadlet’s call — will bend hair cells at the base of the inner ear.
Low frequency ones, such as the thud of a scientist’s foot on the forest floor, tickle hair cells farther inside.But frogs don’t have these well-organized ears. That includes two species of pumpkin toadlet — Brachycephalus ephippium (BRAK-ee-she-faal-us Eh-FIF-ee-um) and B. pitanga. “The weird part about these frogs [is that] they don’t have a middle ear that seems to be important,” Goutte says. “But they have a call.”
The toadlets are very tiny, and so is their chirp. “This is the softest call I’ve ever heard,” Goutte says. To detect it, he says, “You need to know what you’re listening for.” Indeed, she had to strain to pick up their chirps. That led them to question whether the toadlets, which lack a middle ear, could hear their own calls.
To find out, Goutte spent two years in the laboratory and the forest working with the tiny animals. They were not always happy to have her around. “They do this angry arm-waving,” she says. “It’s supposed to be scary,…
The post Pumpkin toadlets can’t hear themselves talk appeared first on FeedBox.