These salamanders get around on ‘lakes of blood’
Controlling blood flow to their toes may help the amphibians stick to, and unstick from, their surroundings
Animals come with all kinds of things at the ends of their toes: nails, claws, talons. But the Aneides genus of salamander has them beat with translucent toes that inflate with blood.
To help understand the purpose of these toes, which 19th century biologists called “lakes of blood,” a team of researchers brought in a natural history cinematographer, who recorded the gold speckled salamanders’ digits up close. The filmmaker’s breakthrough was using a motorized camera sled beneath a clear platform to record the animals.
The team plopped three wandering salamanders (Aneides vagrans) onto the platform, which was oriented either horizontally or vertically to simulate the amphibians’ tree-climbing lifestyle. The camera recorded a single toe until the salamander lifted it up.
The salamanders seemed to adjust their toe blood flow depending on whether they were sticking to or unsticking from the platform, the team reports this month in the Journal of Morphology. Immediately before lifting their toes, the amphibians appeared to fill them with blood, as seen in the video above. While clinging onto the vertical platform, the salamanders kept their toes drained.
The amphibians might be adjusting their toe shape, the researchers propose. Higher blood flow could inflate the toe, like a soccer ball, reducing its contact with the ground and making it easier to unstick. (The video above shows an engorging toe’s surface expand by 5%.) Lower blood flow could do the opposite, flattening the sticky toe against surfaces when hanging on for dear life. The team also showed the salamanders may fill and drain each side of their toes independently, providing fine-tuned toe shape adjustments.
It costs energy, and skin, to repeatedly peel an adhesive toe off of tree trunks and branches. But slipping is even worse. Salamanders’ inflatable digits may solve both problems.
