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.

Fantastic Fire Salamanders – Salamandra salamandra

Slimy and sublime, but do they really “live in fire”?

Fire salamander head shot with view of parotoid glands. Photo by Didier Descouens.

Salamandra salamandra

The name European (or fire) salamander covers a number of salamander subspecies generally found in the mountain forests of western, central and southern Europe, although some populations can be found in North Africa and the Middle East.  There are 13 subspecies; all varying in colour, behaviour and adaptations, but generally fire salamanders are sturdy looking amphibians with a variety of yellow to orange markings on their back. Adults can grow up to a foot long and have been known to live for as long as 50 years in captivity, but ages of 30+ have been recorded in the wild!

Most of these secretive salamanders inhabit moist woodlands where they like to hide under rocks and logs and dig into the leaf litter. Although the adults are terrible swimmers they are never far from the freshwater streams and small pools in which they begin their lives.  Fire salamanders are most active at night, but can be found out and about on damp, overcast days; any time that you are likely to find slugs, worms and other goodies creeping about for hungry amphibians to snack on!  Salamanders catch their prey by sneaking up on an unsuspecting bug and firing their super-sticky tongue out… Gulp! Look at the video below for some fire salamander hunting behaviour.

Water babies

Like all amphibians, fire salamanders spend part of their lives in water. As adults they are poor swimmers, but their larvae need to spend the first 3 months in water (breathing through gills) before metamorphosing into tiny brightly coloured adults and leaving their aquatic birthplace.

Mating between male and female fire salamanders usually takes place in the cooler months, before the winter hibernation.  After blocking the female’s path and rubbing her with his chin the male plants a sticky spermatophore onto the ground and then sala-manhandles (sorry) the female until her cloaca is positioned over it. After fertilization the eggs develop internally.  When the eggs are ready to hatch into larvae, often in the following spring, the female will lay them directly into water where they will immediately hatch.  This process, called ovoviviparity, is common in many aquatic vertebrates, but a few sub-species of Fire salamander also give birth to live young – viviparity!

Creatures of habit, most fire salamanders return to the same cave, crevice or log every day and generally stick to foraging from this location. Some individuals have even been recorded using the same hibernation place for over 20 years! The actual distances that an individual salamander can range for food is quite large, on average around 500m².

Toxic to the touch

An animal which is fairly sluggish and confined to the ground, the fire salamander is vulnerable to predation from other vertebrates, but has a cunning adaptation to discourage being eaten. Upon closer inspection, the upper dermis of all subspecies of fire salamander is covered in small glands which secrete both protective mucus and a powerful neurotoxin.

The compound samadarine isolated from fire salamander skin secretion. Image from Wikipedia.

Two major alkaloids, samandarine and samandarone have been isolated from these skin secretions. These compounds are skin irritants and also disrupt the vertebrate nervous system causing hyperventilation and convulsions. Some species are capable of actively squirting this poisonous cocktail from the parotoid glands just behind the head.  The yellow and black warning colouration helps predators to identify the potential prey as toxic.

Fire salamanders and people

Despite Salamandra coming from the name for a mythical fire lizard, and their “fiery” colouring, the fire salamander would not survive any type of extreme heat.  It’s thought that the common name for these amphibians originates due to their sudden appearance from logs that have been collected for firewood, which is probably the only time that people normally encountered them.

With 13 subspecies distributed over such a large area, people and salamanders are bound to come in to contact with each other. Although currently designated as a species of “least concern” by the IUCN, fire salamanders are at threat from habitat loss, pollution and climate change.  For a species so dependent on cool, wet conditions long-term changes in weather patterns could influence the range of current salamander populations.  Perhaps their major disadvantage lies in the fact that comparatively little is known about many of the subspecies.  Some, such as Salamandra salamandra terrestris, are now commonly kept as pets so much of what we know about their behaviour has been recorded from captive populations.  But those subspecies found in more remote areas are poorly understood and therefore difficult to protect. There is also a tendency to focus only on the aquatic stage in conservation research, but the adult population is just as vulnerable to habitat change.

Fancy seeing a fire salamander in the flesh?  Head to your nearest zoo or wildlife park, they make great exhibits so most places will have them! Check out the video below for some more fire salamander action in their natural habitat.

Pea frog of Borneo – Microhyla nepenthicola

© Prof. Indraneil Das/ Institute of Biodiversity and Environmental Conservation

The miniscule  Microhyla nepenthicola – also known as the mini or pea-frog – inhabits the heath forests of Borneo in SE Asia (see map below).  It was only formally described and named by Conservation International scientists in autumn 2010 (more information here), although it had been well documented for over 100 years.

Incredibly, whilst well-known to scientists, it had previously been thought that this tiny amphibian was a juvenile of other frog species in the genus Microhyla (which itself is populated only by tiny frogs!).  However, after tracking the diminutive frog’s unfamiliar, rasping call (only adult frogs emit calls) as it rippled through the rainforest in Kubah National Park around sunset, researchers found healthy populations living in and around the pitcher plants which thrive in the humid, shady conditions.

Listen to the pea-frog’s call

Pitcher plants: © Prof. Indraneil Das/ Institute of Biodiversity and Environmental Conservation

Many species of pitcher plants that grow in this habitat are carnivorous, trapping and digesting unwitting small insects lured in by bribes of nectar or visual lures (for more on carnivorous plants, see the intriguing bladderwort in the Cabinet).  Insects become trapped in liquid at the base of the pitcher, where they drown and dissolve.  However, improbably, this same liquid is where the pea-frog lays its spawn, and where its tadpoles develop until they emerge as adults.

© Prof. Indraneil Das/ Institute of Biodiversity and Environmental Conservation

The adult frog measures between 10.6 and 12.8mm (just look at how that compares to a coin in the picture, left!), and is the smallest known frog in the so-called “Old World” (which includes Asia, Africa and Europe).  Its “discovery” emerged from expeditions by Conservation International and IUCN’s Amphibian Specialist Group around the world in the hope of rediscovering 100 species of “lost” amphibians – animals considered potentially extinct but that may be holding on in a few remote places. You can find out more about this initiative here.

The Cabinet of Freshwater Curiosities is a place to collect and celebrate curious freshwater species, and the idea that there may be more, similar “curiosities” like the pea-frog awaiting discovery is extremely exciting.  If you have any curiosities of your own to contribute, we’d love to hear from you as we’re keen to feature more “guest curators”!

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The Hairy Frog – Trichobatrachus robustus

Hairy frog (source)

Cameroonian ‘horror’ frog breaks own bones to claw off attackers!

The Spanish saying “Cuando las ranas críen pelo” translates roughly as ‘when frogs grow hair’ – a phrase similar to the English ‘pigs might fly’ – meaning something that is very unlikely to happen.  Incredibly, this curious amphibian doesn’t only grow hair-like tendrils, but also – remarkably – has the ability to intentionally break its own bones as a means of unleashing a sharp claw from its feet to repel predators!  When frogs grow hair, indeed…

Native to the highland streams of the Cameroon in West Africa, the hairy – or ‘horror’ – frog (Trichobatrachus robustus) is prized by local hunters as a tasty delicacy, eaten roasted whole over a fire.  However, hunters have learnt to use long spears and machetes to hunt this formidable frog, keeping well out of reach of its razor-sharp claws.

IUCN range map for the hairy frog (Image: IUCN)

When threatened, this adaptable amphibian tenses the muscles in its hind feet, causing a claw – very similar in shape to a cat’s claw – to break free from the foot bone to pierce the frog’s toe.  A cunning defence mechanism, the frog’s ability to pierce its own skin parallels the Wolverine-like ability of a previously featured curiosity, the Spanish ribbed newt, to develop ingenious means of foiling would-be predators.  Indeed, the British travel writer and explorer Gerard Durrell wrote with pained accuracy about the pointed success of the hairy frog’s claws in drawing his blood in The Bafut Beagles.

Hairy frog specimen (source: WIkipedia)

However, it is yet to be discovered how the frog retracts the claw after being threatened – if it is retracted at all.  Amphibians generally have excellent abilities to rapidly regrow skin over healing wounds, so the production of the claw is unlikely to be more than a minor inconvenience to the frog.

During the breeding season, male hairy frogs develop hair-like strands of skin called papillae.  These curious flowing locks allow the frog to breathe for longer underwater – a process called cutaneous respiration – when guarding unhatched eggs.

Another incredible amphibian for the Cabinet of Freshwater Curiosities, with endlessly fascinating and inventive adaptations to its environment.

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Spanish ribbed newt – Pleurodeles waltl

Spanish ribbed newt (image: wikipedia)

Intergalactic amphibian’s superhero defence mechanism

One species of amphibian has evolved a bizarre and painful sounding defence mechanism. When threatened the Spanish ribbed newt pushes out its ribs until they pierce through its body acting as a row of barbs – in many ways a real-life example of the mutant comic book hero Wolverine’s super powers!

But there is even more to the story. At the same time as pushing its ribs out the newt begins to secrete poison from special glands on its body. The poison coated ribs create a highly effective stinging tool, injecting toxins through the thin skin in predator’s mouths.  The newt’s effective immune system and collagen coated ribs mean the pierced skin quickly regrows without infection.  Curiously, the newt seems to experience no ill-effects from being coated in poison!

First noticed by scientists in 1879, the newt’s extraordinary adaptation has only recently been fully understood through the use of x-ray technology.  Native to the southern Iberian Peninsula (Spain, Portugal, Gibraltar) and Morocco, this large (30cm +) newt inhabits the cool, dark waters of ponds and wells.

Amazingly, since the 1980s, the Spanish ribbed newt has been repeatedly flown into outer space.  The newt’s unique reproductive and regenerative characteristics mean that it is highly useful for scientific experiments on the physical effects of outer space.

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Panamanian golden frog – Atelopus zeteki

Panamanian golden frog in Buffalo Zoo, USA (image: wikimedia)

Alchemical amphibian communicates in stream-side semaphore

The Panamanian golden frog is native to Panama, living around mountainous streams in tropical forests. Like other frogs and toads, the golden frog is capable of secreting highly toxic poison through it’s skin to help protect itself from predators.

These frogs are highly unusual as they use a form of semaphore to communicate, waving at rivals and prospective mates. This adaptation is thought to have evolved in the golden frog because of the noise of their fast-moving streams habitat drowning out their calls. Below is a rare video of this behavior, filmed by the BBC One for the “Life in cold blood” in 2007:

Shortly after filming for the BBC series, these frogs had to be rescued from the wild, due to the threat of the suffocating chytrid fungus. The deforestation of their habitat, water pollution, and over collection for the pet trade are also responsible for the decline of their population.

A waving golden frog

A waving golden frog (image: wikimedia)

The Panamanian golden frog is something of a national symbol, appearing on state lottery tickets and in local mythology. Fascinatingly, it is thought that when the frog dies it turns to gold. It is also believed that the frog brings good luck to those fortunate enough to see it. In 2010 the Panamanian Government passed legislation recognizing August 14th as National Golden Frog Day.

The golden frog is on the IUCN Red List as a critically endangered species. Atelopus zeteki may have been extinct in the wild since 2007, date of the last wild sighting.
More information:

  • Project Golden Frog is an ongoing conservation project which connects the Republic of Panama and the United States, in an effort to ensure the survival of this species. Plans for captive breeding in Panama are being supported by Project Golden Frog.

Captive breeding programs for this species are already in place at a number of zoos, including:

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