Up in the canopy of Northern California’s old-growth coast redwoods, about 100 feet above the ground, lives a community of skydiving salamanders. With mottled brown skin and a body small enough to fit on a credit card, the wandering salamander (Aneides vagrans) can go its entire life without touching the forest floor. But when disturbed, it might take to the air.
Though they have no wings (or even wing-like membranes like flying squirrels), these tree-dwelling amphibians can land big jumps. To figure out how they pull it off, scientists dropped salamanders into a wind tunnel, where it became clear that they’re natural skydivers. Thanks to a flat torso, flexible tail, and large feet, wandering salamanders can slow their fall and even adjust their positions mid-leap. The biologist who first described the behavior wants to know how these salamanders take off and land—and the secret may lie in their distinctive blood-filled toes.
“When I tell [people] salamanders can glide from branch to branch or glide back to their tree trunk, they’re like, well, how the heck do they stick the landing?” says Christian Brown, a postdoctoral researcher in the Department of Integrative Physiology and Neuroscience at Washington State University. “This toe stuff could be the answer.”
Brown is the lead author of a paper recently published in the Journal of Morphology that gets up close and personal with salamander toes. He and his research team discovered that wandering salamanders can quickly fill, store, and drain the blood in the tips of their toes to make it easier to move through their habitat high in the redwoods.
It’s unusual for a creature that breathes through its skin and needs constant moisture to find a home in the treetops. But the unique environment of the Pacific Coast makes it possible. “Part of their secret is coastal fog,” says Brown. “The other half of the secret is the fern mats that absorb that coastal fog and rain like a sponge.” High up in the canopy of old-growth forests, ferns and other plants grow in the crooks between branches, providing a habitat for all kinds of creatures. “The bigger, wetter fern mats have more salamanders,” Brown explains.
Wandering salamanders belong to the genus Aneides, also known as climbing salamanders. Most North American salamanders make their homes on the ground or burrowed underneath it. But, as their name suggests, climbing salamanders set their sights a little higher. These animals are experts at ascending vertical surfaces, thanks to their prehensile tails capable of grabbing onto branches and their square-shaped toes. These adaptations have captured the attention of scientists for more than a century.
The tips of their square-shaped toes have translucent skin covering spots of bright red that 19th-century naturalists vividly described as “lakes of blood.” Their function has long puzzled scientists; Some theorized that they played a role in oxygenating the blood, or preventing the toes from drying out. Then, while filming salamanders for a documentary in 2021, Brown noticed something unusual about their toes.
They were on display in unusually striking detail, thanks to the high-powered camera lenses being used. As one salamander began to move, blood rushed into the tips of its toes. The first time Brown noticed it, he and camera assistant William Goldenberg, who is a co-author on the paper, knew they had something special. “His eyes were all wide and he gave me a big smile,” Brown recalls. They had to move on to the next part of the shoot, but neither forgot about what they had seen.
They brought a few specimens into the lab to get an even closer look. Three salamanders were placed onto a transparent viewing platform and filmed through a magnifying lens focused on their toes. By tracking the flow of blood as the salamanders moved around, the research team saw sinuses at the tips of the toes rapidly fill up in the moments just before take-off (or “toe off,” as they call it).
Brown compares the toe tips to little balloons. When deflated, more of the toe can be in contact with an uneven surface like tree bark. When inflated with blood, less of the toe touches the surface, making it easier to leap off.
And the whole process is powered by the anatomy of the salamander’s foot. “It’s something that’s just happening on a mechanical level,” says Brown, “so all 18 [toes] can work in sync, without having to send any signal.”
This adaptation gives these tree-dwelling salamanders the dexterity needed to navigate the varied surfaces that make up the redwood canopy—not just tree bark, but also fern mats and slippery leaves. The toes may even work as a shock absorber, making it easier for wandering salamanders to land their leaps between the world’s tallest trees. Brown plans to do further research to understand the mechanism and to see if it extends to other salamanders.
“This species is truly inspiring,” says Brown. “They’re counterintuitive, they’re sort of an enigma, and they always impress.”
Article by:Source: Michelle Cassidy
