Tag: frogs

Coin-sized frog becomes mite-y thanks to poisonous diet

By Ed Yong | November 4, 2010 9:00 am

Monte_Iberia_eleuthMiguel Vences was dissecting a frog no bigger than his fingernail when he smelled an unusual acrid smell. “Maybe it can be compared with vinegar,” he says. “It is a totally different smell, but somehow the same kind of bitter-burning feeling when you get it into your nose.” He remembered the distinctive scent from his experiences with other species of frogs, all of which have powerful poisons in their skins. He reasoned that the species he was cutting open – a beautiful Monte Iberia eleuth – was similarly armed with toxins. A chemical analysis of its skin confirmed Rodriguez’s suspicion. The frog’s skin was laced with toxins, including a group of muscle-paralysing poisons called pumiliotoxins that are common among poison dart frogs.

Read More

Pocket Science – belly-flopping frogs, and fattening marmots

By Ed Yong | July 23, 2010 9:00 am

Not Exactly Pocket Science is a set of shorter write-ups of new stories with links to more detailed takes by the world’s best journalists and bloggers. It is meant to complement the usual fare of detailed pieces that are typical for this blog.

Frogs evolved to jump before they perfected landings

Most frogs are can leap large distances in a single bound, jumping forward with a thrust of their powerful hind legs and landing gracefully on their front ones. But it wasn’t always like this. A study of one of the most primitive groups of frogs suggests that the first frogs landed in an awkward belly-flop. These animals evolved to jump before they perfected their landings.

Virtually all frogs jump and land in the same way. But Richard Essner Jr from Southern Illinous University discovered a unique leaping style in the Rocky Mountain tailed frog. This species belongs to a group called the leiopelmatids, more commonly (and accurately) known as the “primitive frogs”. Using high-speed video footage, Essner showed that the tailed frog’s landings are an awkward mix of belly-flops, face-plants and lengthy skids. Only when it grinds to a halt does it gather its outstretched limbs together. By contrast, two more advanced species – the fire-bellied toad and the northern leopard frog – rotate their limbs forward in mid-air to land gracefully. The tailed frog managed to jump a similar distance, but its recovery time was longer.

These results support the idea that frogs eventually evolved their prodigious jumping abilities to escape from danger by rapidly diving into water. Landings hardly matter when you’re submerged and the ability to pull them off elegantly only evolved later. Essner thinks that doing so was fairly simple – if the tailed frog starts pulling its legs in just slightly earlier, it would land with far more poise. This simple innovation was probably a critical one in frog evolution. The primitive frogs never got there, but they have other ways of coping with their clumsy crash-landings. They’ve stayed very small to limit the injuries they sustain, and they have large shield-shaped piece of cartilage on their undersides to protect their soft vital organs.

Reference: Naturwissenschaften http://dx.doi.org/10.1007/s00114-010-0697-4; Video by Essner; soundtrack by me.

More on frogs: Tree frogs shake their bums to send threatening vibes, pesticide-stricken frogs, ‘Wolverine’ frogs, a lungless frog, and seven habits of highly successful toads

Marmot

Changing climate fattens marmots

The media is rife with tales of animals from polar bears to corals suffering as a result of climate change. But some species stand to gain from the rising global temperatures. In Colorado’s Rocky Mountains, warmer climes allow the yellow-bellied marmot to awaken from its winter hibernation earlier. With more time available to eat, they become bigger and so do their populations. In just three decades, their numbers have tripled.

Arpat Ozgul from Imperial College London studied a 33-year census of Colorado’s marmots, where individuals have been tracked over their entire lifetimes. These rodents spend the winter hibernating in their burrows. But since 1976, they have been waking up earlier and earlier in the year, presumably because of a rise in warm days. That gives them more time to eat and grow before their next hibernation, and the adults have become around 10% heavier. Ozgul found that being fatter offers many advantages for a marmot – females are more likely to breed, youngsters grow more quickly, and adults are more likely to survive their next bout of hibernation.

It’s no surprise that their population has shot up dramatically, although surprisingly, this wasn’t a gradual process. Their numbers seemed to be fairly stable but they passed a tipping point in 2000 and have skyrocketed ever since. By modelling the changes in their bodies over time, Ozgul concluded that the marmots haven’t changed much genetically – their extra pounds are the result of their response to environmental changes. For example, the bluebells that they like to eat declined after 2000, which might have prompted them to seek other fattier foods.

But Ozgul worries that this boom period has a bust on the horizon – it’s a short-term response to warmer climate. These are animals that are adapted to chilly mountainous temperatures and they don’t fare well in heat. If temperatures continue to rise and summers get longer and drier, their health might suffer and their populations might crash.

More on this story from Jess McNally at Wired and Lucas Laursen at Nature

Reference: Nature http://dx.doi.org/10.1038/nature09210; image by Ben Hulsey

More on climate change and animal populations: The rise of “weedy” mice, the mystery of the shrinking sheep, lost clownfish, marching emperor penguins, and declining amphibians and reptiles

Read More

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

Read More

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Not Exactly Rocket Science

Dive into the awe-inspiring, beautiful and quirky world of science news with award-winning writer Ed Yong. No previous experience required.
ADVERTISEMENT

See More

ADVERTISEMENT
Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »