Every once in a while, the natural world offers up a bit of smirk-worthy evolution ... most recently, this Simpsons-impersonating water-frog (Telmatobius ventriflavum) from Peru.

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Images: A. Catenazzi (left) & FOX (right)

The brightly coloured frog, whose name translates to 'yellow belly', was discovered during a survey near the Pisco River in the Andean Highlands of Central Peru. "Finding such a beautifully yellow and marigold coloured species was certainly a pleasant surprise," says Dr Alessandro Catenazzi, who described the frog this week in the journal ZooKeys. "I knew the moment we found these frogs that they had to be new." 

What makes the flamboyant frog particularly interesting is that it had actually been found before. But nobody noticed! "The species had been collected by other researchers, and there were well-preserved specimens in museum collections," explains Catenazzi. "It is a bit unusual for such a distinctive species to remain unnoticed. However, the previously collected specimens were juveniles or sub-adults, and that might have complicated identification."

Once the frogs are dunked into a preservative bath, their bright colouration, which is not as vivid in juveniles, quickly fades. After they become 'froggy pickles', the specimens take on a duller grey pigmentation more typical of other Telmatobius species. Catenazzi adds that because of this quick-fading complication, scientists steer clear of using colour as a distinguishing factor when describing new species but even the commonly used diagnostic traits (skin smoothness, for example) are only reliable for identifying the adults of the new species.

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The frog was found near the drainage point of the Pisco River. Image: A Catenazzi

Like many amphibians that have set up camp in the high Andes, the new water-frog is at risk from human activity. And while damming, contamination and the development of large-scale infrastructure like reservoirs and roads affect the entire Andes ecosystem, Telmatobius frogs in particular face a far stranger threat: 'frog juice'. The concoction is sold as an aphrodisiac in the food markets of the Peruvian capital (warning: this video may be disturbing to some). Catenazzi does note that frogs considered 'shake-worthy' are usually larger in size than the new species, which is good news for this adorable yellow-bellied amphibian.

During the survey, the team found traces of the devastating chytrid fungus, B. dendrobatidis, which kills frogs by infecting and thickening the outer layer of skin (an especially unpleasant way to go if you happen to 'breathe' through your skin). The fungus has been linked to extinctions in North and South America and Australia, and is known to affect most of the 6,000 known frog species. "Chytrid is a big problem in the Andes and it is a likely cause of extinction for several species that were previously distributed [there]," says Catenazzi. "The hope is that this population will continue to persist despite the presence of the fungus."

The team calls for future studies to determine the distribution of the species, so that conservation plans can be formulated. "There is so much biodiversity awaiting to be properly identified in tropical countries such as Peru. There are tens to hundreds of species awaiting description certainly many of these species are sitting right now in some jar but taxonomic work requires comparison with specimens deposited in many collections. This is often time-consuming work that requires great dedication."

What other stunning new discoveries are hopping their way through the world's rivers ... or sitting silently collecting dust on museum shelves?