A newfound species of lungless salamander from Arkansas seems to be sipping from a fountain of youth.
From the outside, the recently discovered Ouachita streambed salamander (Eurycea subfluvicola) looks like the larval form of a related species, the many-ribbed salamander (Eurycea multiplicata). But on the inside, the “remarkable” amphibian is obviously an adult, with a fully developed reproductive system, a new study says.
The phenomenon of adult organisms keeping a youthful appearance, called paedomorphism, is well known in nature. But E. subfluvicola is the most extreme example found in salamanders in more than 70 years, according to scientists, and the first ever found in Arkansas’ Ouachita Mountains (map).
Compared with its relative, the many-ribbed salamander, the new species has a shorter and narrower head; a flatter, longer snout; and darker, more depressed eyes. Most noticeably, the new salamander doesn’t have the trademark black stripe that runs down its relatives’ heads and noses, according to the study, published April 11 in the journal Zootaxa.
As with any animal family, it’s extremely rare to find a new species living “under the same rock” as its closest relative, said study co-author Mike Steffen, a biology Ph.D. candidate at the University of Tulsa in Oklahoma, who first found the new animal.
On May 23, 2011, Steffen was collecting many-ribbed salamanders from a mountain creek in Lake Catherine State Park. Short on adult samples, he scooped up a few larvae.
Back at the lab, he dissected the larvae and ran genetic tests. One contained developing eggs, but he thought, “Eh, whatever, it’s just an anomaly,” and moved on. (Also see “U.S. Giant Salamanders Slipping Away: Inside the Fight to Save the Hellbender.”)
When the tests came back, though, one was “really different.” He assumed it was a mistake, but a quick look at his field notes revealed that the unique results belonged to the same sample that had contained the developing eggs. So, it hadn’t been an anomaly—the specimen had been a mature adult, disguised as a larva.
With co-author Kelly Irwin, of the Arkansas Game and Fish Commission, Steffen sequenced a few more of the odd animal’s genes and found the same result. They’d found a new species of paedomorphic salamander.
Confirming the new species meant finding another specimen—and that would take another two years.
Confirming the Find
The spring of 2012 was drier than usual—not good conditions for salamanders—and Steffen failed to find a matching salamander. He again started to wonder if he’d made some kind of mistake. Then, on an unseasonably warm day in February 2013, Steffen and Irwin scooped up a salamander identical to the 2011 specimen. A month later, Steffen found several more.
“You can see through the belly really easily,” Steffen said, and “you can look for reproductive organs if you move them around a little bit.” When he saw mature testes in the young-looking salamanders, he knew he had the right species.
Ultimately, he collected and tested 24 additional animals, which confirmed the discovery of a new species.
Why E. subfluvicola evolved to disguise itself as a youngster is unknown, but the scientists suspect that its youthful form gives it access to an otherwise unexploited part of the streambed and prevents it from breeding with the related species.
According to their genetic research, the team estimates that E. subfluvicola and E. multiplicata became separate species about 18 million years ago.
Right Under His Nose
Despite thoroughly searching the region, the scientists found E. subfluvicola in only two areas of the same creek system, and its rarity should be of “immediate conservation concern,” according to the study. (Read about vanishing amphibians in National Geographic magazine.)
“There could be other paedamorphic salamanders,” Steffen added, explaining that many researchers do not collect larval samples. They could be stepping right over new species without knowing it—just as he nearly did in May 2011.
“If we happened to find three many-ribbed salamander larvae on that day instead of two many-ribbed and the new species, we would probably never have known about this species.”