Frog bladders seek out and get rid of foreign objects
Researchers studying frogs have discovered that frogs and toads of several different species have a very strange ability– they can shuttle large foreign objects down to their bladder for removal. Scientists figured this out after radio tagging frogs only to find some time later that the frogs had either pissed out the tags or the tags were sitting in the bladder waiting to be pushed out. That’s gotta burn.
“This is an extraordinary evolutionary trick,” said Rick Shine, an evolutionary ecologist at the University of Sydney who wasn’t involved in the study. “It wouldn’t surprise me if we continue to find this ability in other animals. Natural selection has had a few hundred million years to solve tough problems organisms encounter.”
Christopher Tracy and his team came across the amphibian ability while studying heat regulation in Australian green tree frogs. The team implanted tiny radio transmitters deep in the amphibians’ peritoneal cavity, which lies just outside the peritoneum — a membrane containing the major organs of most animals.
After a few weeks of living in the wild, however, about 75 percent of the frogs’ transmitters were found in their bladders. Tracy and his colleagues also found some on the ground without any signs of frog death, including being eaten by a predator, disease or other explanations.
“We thought there was a more mundane explanation until we started retrieving transmitters in frogs, and they were in the bladder,” Tracy said. “At that point we connected the dots.”
Back in the lab, Tracy’s team put their hypothesis to the test. They enlisted five green tree frogs and five cane toads, implanting small inert beads in each the same way they implanted the radio transmitters. Each tree frog expelled its bead within 23 days. One cane toad also gave its bead the boot, and the beads in the other four toads had migrated to their bladders.
