Category: Amphibians

The olm: the blind cave salamander that lives to 100

By Ed Yong | July 20, 2010 7:00 pm


In the caves of Slovenia and Croatia lives an animal that’s a cross between Peter Pan and Gollum. It’s the olm, a blind, cave-dwelling salamander, also called the proteus and the “human fish”, for its pale, pinkish skin. It has spent so long adapting to life in caves that it’s mostly blind, hunting instead with various supersenses including the ability to sense electricity. It never grows up, retaining the red, feathery gills of its larval form even when it becomes sexually mature at sweet sixteen. It stays this way for the rest of its remarkably long life, and it can live past 100.

The olm was once described as a baby dragon on account of its small, snake-like body. It’s fully aquatic, swimming with a serpentine wriggle, while foraging for insects, snails and crabs. It can’t see its prey for as it grows up, its eyes stop developing and are eventually covered by layers of skin. It’s essentially blind although its hidden eyes and even parts of its skin can still detect the presence of light. It also has an array of supersenses, including heightened smell and hearing and possibly even the ability to sense electric and magnetic fields.

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CATEGORIZED UNDER: Ageing, Amphibians, Animals

Tree frogs shake their bums to send threatening vibes

By Ed Yong | May 20, 2010 12:00 pm

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Two males red-eyed tree frogs square off over a female. Fisticuffs will soon ensue and as a final challenge to each other, the males… er… vigorously shake their bums at each other. Their quivering buttocks shake the plants they sit on, sending threatening vibrations towards their rival. This secret line of communication has just been uncovered by Michael Caldwell from Boston University. To decipher these messages, he has used a hi-tech combination of infrared cameras, saplings rigged with accelerometers and even a cybernetic Robofrog.

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Not Exactly Pocket Science – panic aboard the Titanic, the rise of polar bears and emasculated frogs

By Ed Yong | March 2, 2010 9:30 am

I’m trying something new. Right from the start, I’ve always tried to write fairly long and detailed write-ups of new papers but this means that on any given week, there are always more stories than time and my desktop gets littered with PDFs awaiting interpretation.

So, I’m going to start doing shorter write-ups of papers that don’t make the cut, linking to more detailed treatments on other quality news sources. This is something that I hope science journalists will do more of. It stems from a Twitter conversation where I asked if I should (a) write up short versions of these stories, (b) ignore them, or (c) link to other pieces. People chose a combo of A and C. And if we’re being honest, I was really pleased with “Not Exactly Pocket Science” and the name needed a feature to go with it!

These shorter pieces will still be written from primary papers rather than press releases or existing news stories. Give me feedback. Do these add to the NERS experience, or do short articles go against what you expect of this blog? And also let me know if you find better pieces on the same stories, or you don’t like the ones I’ve linked to. Let’s turn NEPS into a way of highlighting good journalism elsewhere on the web too.

Panic on a sinking ship – Titanic vs Lusitania

Titanic.jpgIn 1912, the Titanic famously sank after colliding with an iceberg. Three years later, the Lusitania also met the ocean floor thanks to torpedoes from a German U-boat. Both ships had similar proportions of crew and demographics of passengers. Neither had enough lifeboats and as a result, only about a third of the passengers on either vessel survived. Over a thousand people died in each tragedy. But Bruno Frey thinks that differences in the type of people who died tell us something about human behaviour under crisis situations. The key factor, he thinks, is time.

The Titanic sank in a leisurely 2 hours and 40 minutes, with plenty of time for social norms to influence who made it onto the lifeboats. The Lusitania went under in just 18 minutes, creating a situation where it was literally every man for himself. In both cases, the captains told crew to save “women and children first”. But their orders were only deferred to on the Titanic, where women and children were indeed more likely to survive than other passengers. On the Lusitania, people aged 16-35 (their supposed physical prime) were around 10% more likely to survive than other age groups. Likewise, first-class passengers had higher odds of survival aboard the Titanic, when class issues had enough time to manifest themselves but they actually fared worse than the third-class passengers on the Lusitania.  

I usually enjoy attempts to view history through a scientific lens, but in this case, it’s difficult to see how much you could really tell from two data points though. Grey’s data are certainly consistent with the hypothesis that selfish behaviour is more likely to emerge in crises that unfold more quickly. But so many other factors could have influenced the outcomes – the structure of the ship, the fact that the Lusitania sank during war-time, the fact that they probably knew about the events aboard the Titanic, different perceptions of the odds of rescue, and so on. Indeed, Grey mentions all of these and says that, “There can be no absolute proof of the hypothesis that only time led to such behavioural differences. Ideally, more observations (comparable shipwrecks) are needed to better isolate the potential relevance of time.”

More from Mark Henderson at the Times and Jeff Wise at the Extreme Fear blog

Reference: Frey, B., Savage, D., & Torgler, B. (2010). Interaction of natural survival instincts and internalized social norms exploring the Titanic and Lusitania disasters Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0911303107

Jawbone reveals the rise of the polar bear

Polar-bear.jpgA lots of news coverage is devoted to discussing the fate of polar bears, but it’s their origins that are now getting some attention. A new fossil jaw from Svalbard gave Charlotte Lindqvist the opportunity to trace the history of climate change’s flagship species. Polar bears live and die on sea ice, their remains either sink without a trace or are scavenged, so every new fossil is an exciting find. The new jawbone is approximately 130,000 to 110,000 years old but Lindqvist managed to extract enough DNA from it to sequence the genome of its mitochondria – small power plants within every animal cell, each containing their own genome.

She also sequenced extra mitochondrial genomes from two living polar bears and four brown bears from different areas. A family tree built from these sequences revealed that the jawbone’s owner was remarkably similar to the last common ancestor of brown and polar bears, sitting just at the point where the two lineages diverged. By analysing the carbon isotopes of the fossil’s canines, Lindqvist deduced that this ancient bear ate sea-going mammals just like its modern cousins do.

Together, this single bone paints the portrait of an evolutionary success story. Within 10,000-30,000 years of their split from brown bears, the polar bears had adapted magnificently to their frosty kingdom and risen to the rank of top predator. Within the next 100,000 years, they had spread across the entire polar realm. As Lindqvist says, they’re “an excellent example of “evolutionary opportunism”. Whether they’ll be swift enough to cope with the current changes to their habitat is another matter.

More from Brandon Keim at Wired

Reference: Lindqvist, C., Schuster, S., Sun, Y., Talbot, S., Qi, J., Ratan, A., Tomsho, L., Kasson, L., Zeyl, E., Aars, J., Miller, W., Ingolfsson, O., Bachmann, L., & Wiig, O. (2010). Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0914266107

Common pesticide turns Kermits into Kermitas

Kermit.jpgTheir testicle shrinks, their testosterone depletes, their sperm count falls, and they stop trying to have sex. Becoming emasculated and impotent isn’t a pretty fate for a male frog, but thanks to a pesticide called atrazine, it could be a common one. Atrazine is an “endocrine disruptor”, a substance that mimics the effects of sex hormones in the body. Tyrone Hayes has found that it can chemically castrate male African clawed frogs.

Around 10% of the animals actually became fully functional females despite being genetically male. They could even mate with other males to produce viable eggs (albeit ones that only hatched into genetic males). In others, the changes were less drastic but they were still feminised enough to seriously affect their odds of mating successfully. This isn’t the first time that atrazine has been linked to feminised frogs and according to previous studies, it affects other groups of animals, from salmon to crocodiles, in the same way. In these species, atrazine switches on the manufacture of aromatase, an enzyme that, in turn, stimulates the production of oestrogen. This flood of hormone may also be behind the feminised Kermits.

Frogs and other amphibians are particularly vulnerable to chemicals like atrazine because of their absorbent skins. Indeed, Hayes emasculated his frogs with just 2 parts per billion of atrazine, a dose that animals would frequently encounter in contaminated areas, and well within levels occasionally found in rainfall. Because of the environmental risks, atrazine was banned in the EU in 2004, but the US still sprays 80 million pounds of this persistent chemical every year. Obviously, this study didn’t assess the impact that the chemical could have on frog populations but there’s every reason to suspect it as a “contributor to global amphibian declines“.

More from Janet Raloff at Science News

More on amphibian conservation:

Reference: Lindqvist, C., Schuster, S., Sun, Y., Talbot, S., Qi, J., Ratan, A., Tomsho, L., Kasson, L., Zeyl, E., Aars, J., Miller, W., Ingolfsson, O., Bachmann, L., & Wiig, O. (2010). Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0914266107

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Seven habits of highly successful toads

By Ed Yong | February 5, 2010 9:21 am

Toads are an evolutionary success story. In a relatively short span of time, they diversified into around 500 species and spread to every continent except Antarctica. Now, Ines van Bocxlaer from Vrije University has uncovered the secrets of their success. By comparing the most home-bound toads with the most invasive ones, she has outlined seven qualities that enabled these amphibians to conquer the world. In a common ancestor, these seven traits came together to create an eighth – a pioneer’s skill are colonising new habitats.

Some, like the harlequin toads, are restricted to such narrow tracts of land that they are vulnerable to extinction. Others, like the infamous cane toads, are highly invasive and notoriously resistant to extinction despite the best efforts of Australians and their sporting equipment. This diversity of lifestyles allowed Bocxlaer to search for characteristics shared by the most pioneering of toad species.

She compared over 228 species, representing just under half of all the known toads, and constructed a family tree that charts their relationships. She showed, as others before have suggested, that the family’s fortunes kicked off in South America, around 35-40 million years ago. This was the start of their global invasion. 

Seven qualities make for wide-ranging toads. For a start, the adults don’t have the typical amphibian dependency on constant water or humidity. They have skins that can cope with the drier side of life, giving them a chance to seek out new habitats away from the safety net of moist environments. Secondly, they tend to have fat deposits near their groin, which act as a back-up energy source when food is scarce. Thirdly, they tend to be larger (meaning at least 5 centimetres in length), which also helps to conserve water. Larger animals have larger bladders so they retain more water, and they lose less of it because they have small surface areas for their size.

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South African wildlife – Foamy nest frog

By Ed Yong | January 3, 2010 1:10 pm

This is the last animal we saw on our South African safari, and we found it sitting on top of our conditioner. Thank goodness it wasn’t a leopard.

I reckon it’s a foamy nest frog, so named for its tendency to lay its eggs into a nest of foamy bubbles overhanging a body of water. I always thought this species had a darker colour but apparently, they become almost white in bright sunlight. Charming little tyke, isn’t it?

British wildlife – a photo tour

By Ed Yong | September 13, 2009 9:00 am

The British Wildlife Centre is one of my favourite places in the country. It’s like a small zoo focusing solely on British wildlife and everything in it lives in lovely open enclosures with naturalistic environments (the otters have about three lakes to play around in). It’s a fantastic place to visit, especially for people who’ve most likely only ever seen a badger or a fox as a roadside carcass. Here are some photos from yesterday’s trip:

Badger

Buzzard

Eagle owl

Frog (pool frog?)

Harvest mouse (note size of blackberry for comparison)

Otter

Wotta lotta otter

Pine marten (Britain rocks for mustelids)

Red fox

Red squirrel

CATEGORIZED UNDER: Amphibians, Birds, Mammals

Climate change responsible for decline of Costa Rican amphibians and reptiles

By Ed Yong | December 20, 2008 9:17 am

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Blogging on Peer-Reviewed ResearchMiners used to take canaries into unfamiliar shafts to act as early warning systems for the presence of poisons. Today, climate scientists have their own canaries – amphibians. Amphibians – the frogs, toads and salamanders – are particularly susceptible to environmental changes because of their fondness for water, and their porous absorbent skins. They are usually the first to feel the impact of environmental changes.

The golden toad was one of the first casualties in the great amphibian decline.And feel it they have. They are one of the most threatened groups of animals and one in three species currently faces extinction. The beautiful golden toad (right) was one of the first casualties and disappeared for good in 1989. Even though they are less glamorous than tigers, pandas or polar bears, amphibians are a top priority for conservationists.

The usual factors – introduced predators and vanishing habitats – are partially to blame, but many populations have plummeted in parts of the world untouched by pesky humans. More recently, a large number of these deaths have been pinned on a fatal fungal disease called chytridiomycosis. Hapless individuals become infected when they swim in water used by diseased peers, and fungal spores attach to their skins. The disease had decimated amphibians across the Americans.

But it’s not the only killer – climate change can join their list of enemies. In Costa Rica, warmer and wetter days have led to a loss of rainforest leaf litter that has sent amphibian and reptile populations crashing. The extent of the damage may be even worse than we think. We have very little long-term data on the population sizes of many amphibian species, particularly in the tropics, where the greatest diversity exists. One of the few sites to buck the trend of ignorance is La Selva Biological Station in Costa Rica, which has been monitoring amphibian populations since the 1950s.

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Common pesticide is good news for parasites, bad news for frogs

By Ed Yong | October 29, 2008 5:43 pm

Blogging on Peer-Reviewed ResearchOur amphibians are not doing well. Populations of frogs, toads, salamanders and newts the world over are falling dramatically. Their moist, permeable skins and their need for water to reproduce make them vulnerable to a multitude of threats including drought brought on by climate change, a deadly fungus, and other infectious diseases. Now, we can point an accusatory finger at another culprit – a chemical called atrazine that is second most commonly used pesticide in the United States, and perhaps the world.

Frog.jpgJason Rohr and colleagues from the University of Florida found that atrazine exposes the frogs to larger hordes of parasites. The pesticide encourages the growth of algae that is eaten by snails. They are host to parasitic worms called trematodes (flukes), which use snails as a transit station for their journey into the bodies of frogs. More atrazine means more algae, more snails, more parasites and sicker frogs.

Rohr discovered this tangled web by studying the northern leopard frog, a North American species that, like most of its kin, is in decline. Across 18 wetlands in Minnesota, Rohr looked at local frogs, the parasites they carried and the characteristics of their local environment. They measured everything from the numbers of other species, the soil composition, the patchiness of the habitats and the chemicals in the water, to see if anything in the local environment could consistently explain the severity of trematode infections.

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Swimming, walking salamander robot reconstructs invasion of land

By Ed Yong | October 20, 2008 10:00 am

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Blogging on Peer-Reviewed ResearchMoving robots are becoming more and more advanced, from Honda’s astronaut-like Asimo to the dancing Robo Sapien, a perennial favourite of Christmas stockings. But these advances are still fairly superficial. Most robots still move using pre-defined programmes and making a single robot switch between very different movements, such as walking or swimming, is very difficult. Each movement type would require significant programming effort.

a_badertscher_robot_beach1.jpgRobotics engineers are now looking to nature for inspiration. Animals, of course, are capable of a multitude of different styles of movement. They have been smoothly switching from swimming to walking for hundreds of millions of years, when our distant ancestors first invaded the land from the sea.

This ancient pioneer probably looked a fair bit like the salamanders of today’s rivers and ponds. On the land, modern salamanders walk by stepping forward with diagonally opposite pairs of legs, while its body sways about its hips and shoulders. In the water, they use a different tactic. Their limbs fold back and they swim by rapidly sending S-like waves down their bodies.

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'Wolverine' frogs pop retractable claws from their toes

By Ed Yong | May 27, 2008 7:00 pm

Blogging on Peer-Reviewed ResearchIn the X-Men comics, the superhero Wolverine is armed with three sharp claws on each arm. They extend through the skin of his hand, and the resulting wounds are closed by up his superhuman ability to heal. Now, in a bizarre case of life imitating art, scientists from Harvard University have discovered that a group of African frogs use similar weapons.

Wolverinefrog.jpgThe frogs defend themselves with sharp bone claws on their hind feet but to do so, the animals have to drive the claws through their own skin. It’s an extreme defence that is completely unique in the animal world.

The clawed frogs belong to a family called Arthroleptidae that were discovered in Central Africa more than a century ago. At first, people wondered if the claws just stuck through the skin as a side effect of the preservation process. Alternatively, the frogs may have used them to grip or climb. Their true function as defensive weapons only became clear when naturalists first described actually picking up and handling live animals.

Doing so is a mistake, and anyone who makes it is punished with a series of deep, bleeding wounds inflicted by the struggling animal as it kicks out violently with its claws. The ability is well known to the people of Cameroon, who only ever hunt the frogs with machetes or spears.

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