Four new see-through frogs from Peru

August 27, 2014 • 6:15 am

Have a look at this puppy*; isn’t it gorgeous?

*Yes, I know it’s not a dog, for crying out loud!


It’s a glass frog from Peru, one of four newly-discovered species described in a new paper in Zootaxa by Evan Twomey  et al. (reference and link below, but you’ll get only the abstract, and would have to pay big bucks for the paper. Thanks to Evan for sending me the pdf). There’s also a National Geographic blurb which is more accessible than the 87-page monograph, which goes into detail about the frogs’ discovery, description, anatomy, biogeography, phylogeny (based on both nuclear and mitochondrial DNA), “environmental niche models,”  their vocalizations and so on.  It’s an excellent and comprehensive analysis of this group. And, because I’m a good boy, I went through the whole monograph last night rather than spoon-feeding you what’s in the National Geographic summary. Here are some photos and a few of the authors’ conclusions about the frogs.

 Glass frogs are in the family Centrolenidae, which, according to Amphibiaweb, has 151 species in 12 genera. They’re called “glass frogs” because you can see through their bellies, and also through selected parts of their bodies, as we’ll see below.  Their transparency reveals their viscera: heart (“pericardium”, the sac containing the heart), liver, and other guts. A weird thing: three of the speices have green bones, a first for frogs!
Twomey et al. summarize the data showing that there are 33 species in Peru, and their paper describes four new ones. Here is one—the same one pictured above. It’s Centrolene charapita, and from the vental aspect you can see into its belly.  These pictures and captions are all taken from the paper:
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 This was found at one location: along a stream in northern Peru. The name of the species comes from the resemblance of the pattern on its back to Aji charapita (peppers); here are some of them, which start of green and turn yellow:
The bottoms of hands and feet of C.charapita. See the bones? They’re green! The authors hypothesize that this color comes from the sequestration of a pigment from bile, biliverdin.  Whether or not the green color was simply an accident, or is a result of natural selection (perhaps to aid camouflage) isn’t known.
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Voilà, another new species, Chimerella corleone, named after the patriarch of the Godfather movies. It was named because it has a spike sticking out of the upper arm that males may use to fight each other. (The authors clearly have a penchant for colorful species names, which I like.)  These are very small frogs: C. corleone, for instance, is only 2 cm long: about 0.8 inch.
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Here’s the “type locality” of C. corleone. It would be nice to do field work in such a place!:

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Reproduction in species of Chimerella, including C. corleone (a, b, and d; see caption of figure). Males apparently guard the egg masses, which are laid on leaves, and tadpoles, when they hatch, drop into the water:

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The third new species, Cochranella guayasamani:

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Here are its tadpoles, which also start out transparent but are pink (reasons for the color and transparency unknown). On the right you can see the eggs hatching and the tadpoles dropping off the leaves into the water:

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And the fourth new species, Hylinobatrachium anachoretus, the only one found in cloud forest (2050 m). In (b) you can see the ventral view, with the veins, viscera, and heart clearly visible.  In (e) you can see a male guarding its clutch; these frogs have parental care. Why are they transparent? Who knows?


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Finally, here are ventral views of three species in the genus Hylinobatrachium, showing their transparency. Look at the heart, the veins, and the guts!

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These frogs live in relatively inaccessible places, and even in the places where they live they aren’t common. There are many questions about them, including the reasons for their remarkable transparency), but the answers will be hard to come by. How do you figure out why a frog that is so rare is transparent? What kind of experiments can you do?

h/t: Brian


Twomey, E., J. Delia, and S. Castroviejo-Fisher. 2014. A review of Northern Peruvian glassfrogs (Centrolenidae), with the description of four new remarkable species. Zootaxa 3851:1-87.

17 thoughts on “Four new see-through frogs from Peru

  1. Paint their bellies green? Knit them tiny little sweaters? Not an easy experiment to do, and you’d need to be breeding them in the lab to get enough as well. I can only think the transparency is a spandrel, it isn’t even where it can be seen under normal conditions. Very fascinating.

  2. They are certainly very cute – its the big eyes that do it.

    It always seems a bit surprising that amphibians survive, given that they seem a bit rubbish in comparison to the other vertebrates.

    1. This seems the most parsimonious explanation, though if true we should expect to see other denizens of the same dark places to have similar transparency. Many species of animals that live exclusively in caves are sightless and pigment free, so if what you suggest it true, one might expect similarly transparent species that live in the same places as these frogs.

      Another possibility is identification or mate selection. Perhaps this is just the frog’s version of peacock feathers or a bird’s call.

      Or it may be a spandrel; maybe in these species of frogs their belly skin has some function that results in them being transparent – the transparency is not significant but is a result of these frog’s particular physiology to another function.

  3. My girlfriend has the habit of referring to pretty much all animals as puppies (except for members of the genus felis, those she refers to as “kittehs”) so I got what you were saying!

  4. A couple of posts ago ceiling cat mentioned that frogs(in general?)seem to be ‘cobbled together’ evolution wise.could someone refer me to a paper or two describing this, please.
    Just terminally curious.

  5. I’m not very good at spotting frogs in rainforest (lack of fully binocular vision due to childhood strabismus), but if they happen to be on a sunlit leaf above you the silhouette is pretty distinctive. If there are predators that commonly find treefrogs in that way, that could provide selection for maximising transparency and greenness. This could be investigated by comparing frequency of leaf-sitting behaviour between glass frogs and less transparent green treefrog species in the same habitats, studying the prey-finding behaviour of their visual predators (birds, snakes etc), and optical measurements of the intensity and sharpness of their shadows through leaves.

  6. Remarkable find. I wonder if any of them are toxic like arrowhead frogs. Probably would have mentioned it if they were.

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