A male member of the new glass frog species, Nymphargus manduriacu
Photo: Jose Vieira | Tropical Herping

Many tropical frogs are admired for their stunning coloration, but glass frogs go a different route. The skin on their bellies is at least partially transparent, making their internal organs visible from underneath. Now, another frog joins the of these clear-tummied amphibians—a remarkable little creature from Ecuador, newly described by scientists last week.

An estimated 150 species of glass frogs inhabit a swath of tropical rainforest ecosystems extending through Central and South America, hanging out in mist-slicked trees and shrubs, often along streams. Only a couple inches long, it’s the glass-bottomed boat effect of their see-through undersides that sets these delicate ribbiters apart. In many species, beating, pulsating viscera are plainly visible through transparent skin. It’s like looking through a plastic Tupperware container, except instead of seeing leftover pesto fusilli, it’s a bunch of frog guts.

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Underside of a female Nymphargus manduriacu
Photo: Jose Vieira | Tropical Herping

The “glass” belly might help the frogs stay hidden from predators somehow, according to Juan Guayasamin, a herpetologist at Universidad San Francisco de Quito that led the study describing the new frog.

“But we don’t have any real, hard data related to such an amazing trait,” Guayasamin told Earther.

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Guayasamin and his colleagues first found the new glass frogs while conducting fieldwork in Río Manduriacu Reserve, a nature preserve in northern Ecuador, on the Pacific-facing slopes of the Andes. While some of the frogs were encountered in previous field seasons, it wasn’t until this February that the team—including researchers affiliated with conservation groups like EcoMinga and Tropical Herping—found them in greater numbers. Discovering the frogs at night along a few streams in the reserve, the researchers collected some to take back to the lab, and recorded the calls the males were making—a sound Guayasamin describes as a single, high-pitched “chirp.”

Their results of a close examination of the frogs’ physical features and DNA, published last week in the open-access journal PeerJ, suggest that the Manduriacu glass frogs are a species totally new to science. Not only are the Manduriacu frogs genetically distinct, their unique aesthetic—a mix of light yellow speckles on their back, and missing some webbing between their toes—is a combination not seen in other glass frogs.

The researchers named the little frog Nymphargus manduriacu, its species name in reference to the reserve, the only place it’s yet been found. Unfortunately, this exceptionally small territory mean the glass frog is particularly at risk of extinction.

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Despite being in a reserve, the forested streams the frog calls home are under extreme threats, so much so that Guayasamin and his colleagues already consider Nymphargus manduriacu critically-endangered. Those threats include logging—which is often done illegally, and goes largely unregulated—and an ongoing open-pit gold and copper mining operation in the area.

“Even though the new species is within a private reserve, the reserve itself is within a mining concession,” Guayasamin explaine. “Since glass frogs—as many other species—depend on a high-quality habitat of forest and streams, mining, and other destructive activities such as palm plantations, agriculture or cattle, represent a serious risk.”

Nymphargus manduriacu in the wild
Photo: Jose Vieira | Tropical Herping

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The discovery of Nymphargus manduriacu is an important reminder of the unique and irreplaceable biodiversity that resides in the Río Manduriacu Reserve. For example, the reserve contains the only known population of the Tanadayapa Andean toad, a species that was thought extinct until only a few years ago when it was rediscovered in Manduriacu. The reserve is also one of the last refuges of the critically-endangered brown-headed spider monkey, one of the most imperiled primates on Earth.

Whatever the ultimate fate of these other threatened neighbors, one thing’s crystal clear. In order for the Manduriacu’s frogs with the Saran wrap skin to survive, keeping that sliver of streamside real estate intact and untainted is crucial.

“The main step,” for continued conservation, Guayasamin said, “is to make sure that the habitat is preserved and that stream water is not contaminated by human activities.”

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Jake Buehler is a science writer living on Washington’s Olympic Peninsula with an adoration for the Tree of Life’s weird, wild, and unsung. Follow him on Twitter or at his blog.