Yellowstone National Park is "charismatic mega-fauna" defined. Spend a handful of days in the park and you're likely to spy wolves, elk, grizzlies, black bears, moose and more. But salamanders?
It's well-known in national park circles that Great Smoky Mountains National Park, which hugs the Tennessee-North Carolina border along the southern run of the Appalachian Mountains, is the "salamander capital of the world."
Great Smoky has black-chinned red salamanders, spotted salamanders, marbled salamanders, seal salamanders, over-sized "hellbenders," and even lungless salamanders. But what about Crystal salamanders?
Nope. For those you have to visit Yellowstone.
In fact, until last July few if anyone realized that these salamanders, which almost appear to be made out of clear gelatin, existed in the park. But then Sarah McMenamin, who was conducting research into amphibian phenotypic (aka physical characteristics) and genetic diversity, waded into two murky ponds in the northern end of the park.
That's when she stumbled upon salamanders so lacking in pigmentation that, if she looked closely enough, she could see the blood pumping through the salamanders' tiny hearts. While her first thought was that these perhaps were albinos, the more she and her crew sampled the ponds the less she held onto that possibility.
"After hours of wading around with nets and fishing out dozens of individuals, each as clear as the last, I realized that these ponds contained something truly novel," Ms. McMenamin wrote in an article that appeared in the January edition of Yellowstone Science. "Every individual was so thoroughly devoid of coloration that it was rendered largely transparent, with internal organs readily visible in sunlight."
Hence, the "crystal" moniker that was attached to these unusual amphibians.
Intrigued by this find and curious to learn more, I tracked Ms. McMenamin down at Stanford University, where she's working on her doctorate in the university's Department of Ecology and Evolution.
"My assistants and I pulled out around 50 larvae in an afternoon," she told me. "The actual population must be larger than that. There could be anywhere between a few hundred and a thousand in each pond."
The amphibians, which ranged up to nearly 10 inches in length, are from one family of salamanders, Ambystoma tigrinum melanostictum, the blotched tiger salamander, Ms. McMenamin said. While this salamander species is the only one in Yellowstone, it's actually quite common there, having been found throughout the park, she added.
As to why the "crystal" salamanders are transparent and not blotched like their kin elsewhere in Yellowstone, Ms. McNenamin believes it has to do with the ponds' water -- there is so much clay in suspension that sunlight doesn't fare well in penetrating to the pond bottoms, where the salamanders live. Under such opaque conditions, if you're a salamander it pays to blend into this murky setting.
"I suspect it's due to a lack of UV. Living at the bottom of these very turbid ponds means that they're exposed to almost no light," she said.
And while it's good to be transparent in these specific ponds, it might not be so great in waters with greater clarity, said Ms. McNenamin.
"In these ponds, which have a very high dissolved mineral content making them very light in color, I would say that the amelanistic salamanders have a competitive advantage. In 'normal' ponds, though, these guys would stick out and would be more visible than normally pigmented salamanders," she said.