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See-Through Frogs With Green Bones Discovered in Peru

A photo of a transparent frog, Centrolene charapita
Centrolene charapita, one of four new frog species discovered in Peru. This species is semi-transparent. Photograph by Evan Tworney

Four new species of see-through frogs, three of which reveal green bones, have been discovered by researchers in northern Peru.

Showing their beating hearts and other body organs in x-ray detail, the newfound amphibians belong to the aptly named glass frog family (Centrolenidae).

Uncovered during extensive surveys in the Peruvian Andes, the “four remarkable species” were described August 12 in the journal Zootaxa.

The tiny frogs, which live alongside streams, include Centrolene charapita—named for a chili pepper that the yellow splotches on the back of this species resemble. Curiously, the two specimens that were collected had hind legs lined with fleshy, zigzag protuberances.

“We have no clue” why that is, acknowledged study co-author Santiago Castroviejo-Fisher, a herpetologist at Pontifícia Universidade Católica do Rio Grande do Sul in Brazil. Of the 150 known species of glass frogs, “less than ten have such ornamentation,” he said.

Fellow discoverer Evan Twomey, a frog researcher at East Carolina University in North Carolina, speculated that the leg frills could help to break up the frog’s outline and mask it from predators. “That’s a possibility, but it’s hard to know,” he said.

Gaudy Coloring

Cochranella guayasamini, which like many glass frogs is mostly green where it isn’t see-through, has distinctive yellow circles around the eyes. However, its tadpoles—which emerge from spawn laid on leaves overhanging mountain streams—are a vivid reddish pink before later turning green, according to the study.

The team said this gaudy coloring could be explained by a ramped-up system of blood vessels in the transparent tadpoles’ skin, which enable them to live in oxygen-poor sediments in the streambed.

But again, that’s only a guess: Glass frog tadpoles have barely been studied, and their natural history remains largely unknown, Twomey said.

A photo of the ventral side of a transparent frog, Chimerella corleone
A belly shot of Chimerella corleone, one of three transparent frog species discovered in Peru. Photograph by Evan Twomey

A third new species, Chimerella corleone, owes its mafia clan title to one team member’s obsession with The Godfather novel and film trilogy.

Detected only in the spray zone of waterfalls, the frog hardly looks menacing considering it’s just two centimeters (0.79 inches) in length. However, it does happen to conceal a spike-like bone in its upper arm, Twomey said.

“I guess it’s used for fighting between males,” he added. “So, for a frog that size at least, I’d say it’s fairly ruthless.”

C. corleone, along with the two species so far mentioned, were found to have green bones—a bizarre trait that’s actually widespread among glass frogs. The research team suspects the strange bone coloration is caused by an accumulation of a metabolic byproduct called biliverdin, a green bile pigment.

Green Bones Puzzle

Whether having green bones might in some way be advantageous to the frogs hasn’t been studied, Castroviejo-Fisher said, but “I have noticed that most frogs with green bones are arboreal [dwell in trees].”

A photo of a new species of transparent frog, Hyalinobatrachium anachoretus
Researchers found Hyalinobatrachium anachoretus residing much higher in the mountains than other species in this genus. Photograph by Evan Tworney

The fourth newly described species, Hyalinobatrachium anachoretus, was recorded in cloud forest at an altitude of 6,725 feet (2,050 meters). Other known species in this genus are found up to a maximum elevation of 3,280 feet (1,000 meters), so the find was “very unexpected,” Castroviejo-Fisher said.

The team discovered this frog in large numbers, but only on one particular night. Other nighttime surveys of the same area failed to turn up a single specimen.

The bigger mystery scientists are struggling to solve is why these and other glass frogs allow us to see straight though them. “Without a doubt, the adaptive, developmental, and genomic basis for the transparency of glass frogs is a long-standing question in zoology,” Castroviejo-Fisher said.

In the meantime, the backlog of undescribed glass frogs in South America is mounting. “We have a bunch of new species awaiting description in our offices,” Castroviejo-Fisher said.

The see-through frogs clearly have a lot more to reveal.



  1. bob
    October 13, 2014, 11:49 am

    so cool……………………………………………………………

  2. Jessica Rubino
    Oak Lawn, IL
    September 8, 2014, 9:19 am

    These frogs are awesome! ! I love learning about new species. Vivian from New Mexico, it’s the Wood Frog that freezes solid then thaws. A North American frog. They have a special antifreeze that keeps their organs from getting damaged during the freeze.

  3. Vivian McAlexander
    Socorro, New Mexico, USA
    August 31, 2014, 9:18 am

    Corleone glass frogs are amazing to learn about! Clear with green bones, and so cute. Frogs and toads are like something from science fiction, and they are well worth learning about if you love the strange and the unusual. Frogs that freeze solid then thaw out and are perfectly healthy?! Science fiction? Nope. This is a natural routine. The name of this frog escapes my mind at the moment, but do study frogs! They are like no other little critter on Earth. Have a little fun and relaxation while the world has gone utterly insane and cruel, and learn about frogs to escape for a little bit. “Ribbbbit!” – Vivian McAlexander (A nerd, and proud of it!)

  4. Mike Jones
    August 29, 2014, 7:02 pm

    I saw these a long time ago at the national zoo.

  5. isaac dadzie
    kintampo Ghana
    August 29, 2014, 5:48 am

    i think this is wonderful u guys are doing do in yr reserch keep it up

  6. Hazem
    London, United Kingdom
    August 28, 2014, 2:50 pm

    Amazing discovery
    Yet another proof of how adaptive organisms become over millions of years…
    Hard to believe sometimes but absolutely true to me.
    There is a common theme of utilizing the animals natural proteins to enhance its camouflage, in this case the green bones!
    As a physician I never thought of it as an option yet here it is

  7. Trish Buchhofer
    United States
    August 28, 2014, 7:49 am

    This discovery is amazing causing one to see the uniqueness and beauty of nature. I’m blessed to live in a region on the East Coast of the U.S. where in the summer tree frogs sing every night starting in mid July until September. A welcome sound of summer!

  8. Madelyn
    Buffalo, New York
    August 27, 2014, 8:33 am

    Awesome they are very fascinating. awesome discovery u guys are the best

  9. philippe
    August 27, 2014, 6:28 am

    Ever think that maybe if the bone is green and the skin transparent it could be for sunlight? Maybe these Animals can photosynthesize through their bones…. hehehe farfetched , but it would be cool.

  10. Sergio
    Ghent (Belgium)
    August 26, 2014, 7:05 am

    Keep going Santi!!
    I send you all my support.


  11. Job Ossuret
    Kampala uganda
    August 26, 2014, 4:52 am

    Thats so incredible,i have loved the view and i would love you to give me more of that.

  12. Dwayne LaGrou
    Lapeer, Michigan
    August 25, 2014, 9:29 pm

    Just imagine what we would look like if we were semi transparent. It would definitely put x-ray technicians out of work!!!
    Very cool Guys, Keep up the good work.

    Karachi, Pakistan
    August 25, 2014, 6:18 pm

    I think this species doesn’t exists before discovered 😉 joking ….. great discovery! !

  14. Susan Newman
    Jersey City, NJ
    August 25, 2014, 4:36 pm

    What a fabulous discovery and they are so beautiful too!