A team of Russian scientists has discovered mutant frogs with see-through skin and pink bones – or so the internet will have you believe. 

The story first appeared earlier this week on the Daily Mail and has since popped up on various news platforms. Scientists from Russia's Ural Federal University (UFU), the outlets report, recently discovered a population of frogs with "transparent skin through which their organs, skeletons and even their beating hearts are clearly visible." In the accompanying images, the frogs certainly look the part – but this is not what these amphibian mutants looked like in life.

This is what the frogs actually looked like. Image: Vladimir Vershinin/used with permission

The images used by the Daily Mail actually show dead specimens that have been "cleared and stained", a process formally known as diaphonization, which stains bones and cartilage in bright hues and renders the soft tissues of an animal transparent. The effect allows scientists to observe the internal anatomy of their subjects in a natural state, and is less expensive than CT or other scans, many of which can't "see" soft tissues anyway. In fact, you don't need to be a scientist to try it (though it's important to note that some of the chemicals involved should be handled with care).

The "clearing" of the tissues is the work of the digestive enzime trypsin, which chews up many of the body's proteins but leaves structural collagen intact. You see the frogs' bones as a deep magenta because they have been dyed with a stain known as alizarin red, which is attracted to calcium. 

Other dyes, such as alcian blue, home in on cartilage, and are commonly used to stain the skeletons of sharks and rays. 

A diaphonized bonnethead shark embryo. Image: Dr Adam Summers/Used with permission
A diaphonized butterfly ray. Image: Dr Adam Summers/Used with permission

UFU head of Zoology Dr Vladimir Vershinin and his team diaphonized the frogs, which were found with only a slight pigment irregularity, in an effort to find out if environmental pollutants may have affected their development.

The animals' eyes were found to be darker than usual, suggesting an over-abundance of the pigment melanin. Their bellies, however, appeared slightly translucent, expressing a lack of pigment. On close inspection, you can faintly detect beating hearts beneath the skin – but it's no match for the dramatic appearance of the frogs' diaphonized kin. 

Both the natural and diaphonized (top) frogs appear side by side. Image: Ruptly/YouTube
A look at the ventral (belly) side of the frog reveals the pigment irregularity. Image: Ruptly/YouTube

The scientists have yet to confirm what might be causing the frogs' pigment mutations, but Vershinin suspects that heavily polluted waters may be to blame. One specimen even turned up with an extra digit on each leg.

"A city is a special type of environment where animals are exposed to a complex mixture of pollutants, often acting synergistically," Vershinin wrote in a 2014 study of the area where the frogs were found. "These can be washed in from the terrain and surrounding roads, brought in by atmospheric precipitation and dumped in by businesses and households."

Six-fingered frog. Image: Vladimir Vershinin/used with permission

He adds that city-dwelling amphibians tend to reproduce in small ponds – and as you can imagine, standing water accumulates pollutants much more quickly than streams and rivers do. "It is difficult to forecast the long-term consequences of exposure," he says. 

This story is a good example of real problems – and in this case, real mutants – being buried under bad reporting. Against the allure of "nightmarish" pink-boned frogs, the actual mutations Vershinin observed seem relatively unimpressive. Of the 50 frogs sampled, only two showed evidence of any deformities or pigment irregularities, yet the team explains they could be indicative of environmental changes affecting an array of Russian plants and animals. To find out, amphibian pigmentation specialists will soon be visiting UFU from Japan to perform genetic analysis on the frogs, according to an interview with Ruptly (translated from Russian). 

"It's unfortunate that journalists showed pictures of a normal cleared frog prepared for skeleton study," Vershinin told us via email. 

The misrepresented images were distributed by Central European News (CEN), an agency that has faced criticism for its misleading and sensationalised stories before. Back in 2015, BuzzFeed published a piece on CEN's controversial practices and was subsequently sued by the agency

"The firm’s business model, like that of many other news agencies, is to sell a regular stream of stories and pictures to other media companies, which publish them under the bylines of their own reporters," says BuzzFeed. "In CEN’s case, these include a string of stories from relatively remote parts of China, India, Russia, and other non-Western countries. They tend to depict the inhabitants of those countries as barbaric, sex-crazed, or just plain weird. And often they are inaccurate or downright false."

Funnily enough, you don't need out-of-context images to feast your eyes on see-through frogs. In Central and South America, over 150 species of "glass frogs" in the family Centrolenidae rock the translucent look. 

Invisible skin allows light to pass through the frogs, making it difficult for any lurking predators to see their shadows from below. You may remember Hyalinobatrachium dianae, a glass frog that made headlines for its uncanny resemblance to a certain green Jim Henson character:

Frog Kermit Related Content 2016 07 30

For more on the clearing and staining process, check out this wonderful video featuring Dr Summers from ScienceFriday:


Top header image: Macroscopic Solutions/Flickr