Living at 12,000 feet – Lake Titicaca “scrotum” frog adapted to the high life

Entirely aquatic and one of the largest frogs on the planet, growing up to the size of a salad plate, the Lake Titicaca water frog also makes one of the stranger fashion statements in the amphibian world. Its excessive skin folds, which look like someone put its skin through a taffy-puller and then sewed the result back on, have earned it the whimsical Latin name of Telmatobius culeus – “aquatic scrotum.”

The scrotum frog’s bizarre outfit is actually the perfect adaptation to the cold waters of its high-altitude home. The bottom-dwelling frog is only found in Lake Titicaca, often called the highest navigable lake in the world, sandwiched between Peru and Bolivia. The frog is entirely aquatic, living in the reed beds of the lake and its rivers. Avoiding the oxygen-depleted air, its ornate skin folds and abundance of capillaries allow it to absorb oxygen directly from the saturated water, making up for its tiny lung size and allowing it to stay permanently below the surface – which protects it from the high levels of ultraviolet radiation found in the area. It also benefits from a high number of small red blood cells, which efficiently deliver oxygen and remove carbon dioxide from its body tissues.

Illustration by P. Roetter, Bulletin of the Museum of Comparative Zoology

Illustration by P. Roetter, Bulletin of the Museum of Comparative Zoology

The oddball frog has fascinated people for centuries. Lake Titicaca frogs were believed to have special powers, particularly in bringing  rain: once carried in a ceramic pot to a hillside, the frogs would call in distress, which supposedly sounded to the gods like a plea for rain. Once the downpour began, the pot would overflow and the sacred animals would escape back to the lake. The frog also captured the imagination of its 1876 European discoverer, S.W. Garman – as witnessed by his choice of a name. Jacques Cousteau, searching Lake Titicaca for Inca treasure in the 1970s, was equally enthralled, reporting “thousands of millions” of the frogs, some almost 20 inches long.

These days, such giants are unlikely to be seen. Aside from global threats to amphibians such as the chytrid fungus and invasive species, in this case a trout that preys on its tadpoles, the Lake Titicaca water frog suffers from over-popularity. It is a favorite menu item at tourist restaurants around the lake, and is also taken to Lima markets – where it’s sold as an aphrodisiac. The frogs are skinned and then blended with water, maca (a local root vegetable) and honey into a juice, thought to be the cure for several ailments, including impotence. It is also collected as a pet or curiosity, while pollution, habitat loss, and overfishing of its main prey, the small fish known locally as ipsi, could also be pushing the critically endangered frog towards extinction.

In response, captive breeding programs have been established for the giant amphibians, both around Lake Titicaca and internationally. One possible plan is to farm the frogs for consumption, taking the pressure off those left in the wild, although this could subject the small population to increased risk of disease from large, densely-kept captive populations. Scientists from both Peru and Bolivia are studying the frog, to assess its ecology and feeding habits as a base for captive breeding.

ARKive video – Lake Titicaca frog

Axolotl (Ambystoma mexicanum)

"Ambystoma mexicanum 1" by Stan Shebs - CC-BY-SA-3.0

“Ambystoma mexicanum 1” by Stan Shebs – CC-BY-SA-3.0

Our newest addition to the cabinet comes by special reader request, collected by Cecilia Larraga! Its name, from the Aztec Nahuatl language, means “water monster,” and it’s also known as the Mexican walking fish, but the axolotl is neither a fish, nor can it survive out of water. Its unique lifestyle and almost non-existent range (not to mention its ability to regenerate) make it a curious creature, to say the least!

I don’t want to grow up

Unlike most salamanders, axolotls never go through metamorphosis. With the odd exception, they stay in their larval stage for their entire lives, a condition known as “neoteny.” This is partially what gives the species its bizarre look, since axolotls keep their tadpole dorsal fin, as well as the feathery external gills that stick out like a strange headress. Since they never develop air-breathing lungs, axolotls spend their entire lives underwater. Staying in tadpole stage doesn’t prevent axolotls from reproducing, however; they mate underwater and the females lay their eggs on plants and other available surfaces.

They’re normally black or brown, but pink or white albinos are commonly found in captivity – and sadly, captivity is almost the only place where the fascinating creatures still exist these days. Found only in the former Lake Xochimilco complex in Mexico City, the axolotl has taken a beating as the city grows. Lake Xochimilco and Lake Chalco have been gradually drained to reduce flooding risk and make room for expansion; Chalco has totally disappeared, and the axolotl now clings on in a few remaining canals and small lakes.

Ambystoma mexicanum Photo © Biopix: N Sloth

Ambystoma mexicanum by Biopix: N Sloth – CC-BY-NC

According to research by Dr Luis Zambrano of the National Autonomous University of Mexico, the critically-endangered species lives in only six isolated parts of the Xochimilco system, usually near springs that still have clear, fresh water. Zambrano’s team says there may be only 700 to 1200 individuals left in the wild. Water pollution is another reason the population has crashed; it also has to deal with competition from introduced fish like tilapia and carp. Unfortunately, using reintroductions to boost the wild population might be dangerous, since it would risk introducing the chytrid fungus currently wreaking havoc in amphibians worldwide. However, the axolotl is widespread in captivity – it’s extremely popular both as an aquarium pet, and as a subject of scientific research.

Hey, take a look at this trick!

Biologists are fascinated by the axolotl because it’s an amphibian that never grows up – giving it an amazing ability to regenerate. The species can re-grow entire limbs, heal parts of spinal cord, and even portions of the brain. Axolotls can recover from massive injuries – and can heal over and over again, with no sign of scarring. And it gets better – they’re also over 1,000 times more resistant to cancer than mammals. Scientists are exploring how these unique “superhealing” abilities work, with the hope of (eventually) being able to heal human tissues, improving success for burn victims, transplant recipients, and even cancer patients.

The question is what the chances are for wild axolotls in the meantime: Zambrano and his team are trying to create wild refuges so that these populations, too, can bounce back. The restoration of the Parco Ecologico Xochimilco over the last 20 years is one of the projects to reclaim crucial habitat for this one-of-a-kind animal.

Walking Catfish (Clarias batrachus)

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Source: eol.org. © CAFS

Sometimes being a relentless survivor can be trouble. That’s often the case with invasive species, which use unique qualities evolved in their native environment to take over other areas that don’t have environmental means to control them. This is true of the incredible walking catfish, our new feature in the Cabinet of Freshwater Curiosities.

Wait. A fish that walks?

Curiouser and curiouser, isn’t it? This bizarre, tenacious animal, originally from southeastern Asia, lives in the stagnant waters and mud of slow-moving rivers, swamps, and ponds, as well as ditches, flooded fields, and rice paddies. However, when it gets the urge to move – for example, if it gets stuck in a temporary pool left after a river flood – it can “walk” across dry land to find a new home. This walking is really more of a wriggle: the fish uses its spiny pectoral fins and twists its body back and forth to waddle awkwardly along the ground. It actually breathes air on these journeys, since it has a special organ that supports its gills, working almost like a lung. Walking catfish can survive out of the water as long as they stay moist – instead of scales, their skin is protected by a layer of mucus. Breathing air also allows them to thrive in “hypoxic” or oxygen-poor water, where other species can’t survive.

So it not only walks, it breathes air and lives in an otherwise deadly environment? Cool!

Well, not totally. The same unique adaptations that make the walking catfish so fascinating also make it a particularly troublesome pest – the Encyclopedia of Life has it on a list of 100 of the world’s worst invasive species. It is found across Southeastern Asia including eastern India, Bangladesh, Myanmar, Thailand, Malaysia, Indonesia, Singapore, Borneo, Laos and the Philippines, although it’s difficult to say how much of this is its original range. In Florida, where it was introduced for aquaculture in the 1960s, it spread into 20 counties within a decade, turning the state’s extensive canal system into an invasion highway. By the 1970s, researchers reported as much as 3,000 pounds per acre of invasive catfish in small Florida ponds, and they have also been found in other states as far apart as California and Connecticut, probably released deliberately or accidentally from aquariums.

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Source: eol.org. Image by: Pam Fuller, USGS

The slimy fish is voracious, eating a smorgasbord of smaller fishes, eggs and larvae, crustaceans and insects, as well as aquatic plants and debris. It can “walk” to isolated pools that are safe from many other species, and is a nightmare for aquaculture, walking from one fish farm to the next and gorging on fish stock, causing millions of dollars of damage. Many countries including the US require a permit to possess the fish, although there are still reports of pet stores selling them. However, controlling them is nearly impossible, since they can easily move to new habitats and can also wriggle into the mud and survive for months without food.

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Source: eol.org. © WoRMS for SMEBD

Ok, so not so cool. Does anyone like the walking catfish?

Although it’s got an undeniably bad reputation as an invasive species, in its native range in Asia it is highly valued by both commercial and subsistence fisherman. The fact that it can survive for so long out of water makes it more attractive because fishermen can easily trade live fish. But it’s a bit of a shocker in Florida when you see a school of thirty fish come up out of the sewer to take a stroll down the street!

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