The World’s Smallest Vertebrate – A Tiny New Guinean Frog

Researchers from Louisiana State University have discovered the world’s new smallest vertebrate, a frog so small you could fit two on a dime end-to-end. From National Geographic:

The world’s smallest known vertebrate is a frog the size of a housefly, a new study says.

At an average of 7.7 millimeters long, the newfound Paedophryne amauensis is a hair smaller than the previous record holder, the Southeast Asian fishspecies Paedocypris progenetica, whose females measure about 7.9 millimeters…

It’s obvious “they’re adapting to fill a niche that nothing else is filling,” he said.

Indeed, the frogs likely evolved their tiny sizes to eat tiny invertebrates, such as mites, that are ignored by bigger predators, said study co-author Christopher Austin, a biologist at Louisiana State University in Baton Rouge…

Scientists locate the teensy animals by listening for their calls and trying to zero in on the sources of the sounds—no mean feat, since the high pitch of the calls make their sources especially hard for human hearing to locate.

Austin and graduate student Eric Rittmeyer tried four times to find the frogs before exasperatedly grabbing a big handful of leaf litter and putting it in a plastic bag.

The scientists then combed through the contents until “eventually we saw this tiny thing hop off one of the leaves,” Austin said.

The frogs are so small it’s hard to see their earth-colored skin patterns with the naked eye, so Austin took pictures and then zoomed in, using a digital camera like a microscope.

But photographing the amphibians was just as challenging as finding them. When Austin brought the camera to his eye, the subject would often already be gone.

The new frogs are “incredibly good jumpers—they can jump 30 times [longer] than their body size,” said Austin, whose study was published January 11 in the journal PLoS ONE.

That’s pretty incredible; there are some organisms that seem to straddle the boundaries between different worlds, and this is one of them. I want a report back from this frog on what life in the insect world is like. 

Photograph by Christopher Austin, via National Geographic

The Meaning of Life

The word, not the phenomenon – that’s a story for another blog. Carl Zimmer has an article at Txchnologist on the ongoing disagreements of how to scientifically define life. It seems intuitive that we know what life is – it’s… you know… living stuff. The reality is much less settled:

When NASA says it wants to find out if Mars was ever suitable for life, they use a very circumscribed version of the word. They are looking for signs of liquid water, which all living things on Earth need. They are looking for organic carbon, which life on Earth produces and, in some cases, can feed on to survive. In other words, they’re looking on Mars for the sorts of conditions that support life on Earth.

But there’s no good reason to assume that all life has to be like the life we’re familiar with. In 2007, a board of scientists appointed by the National Academies of Science decided they couldn’t rule out the possibility that life might be able to exist without water or carbon. If such weird life on Mars exists, Curiosity will probably miss it.

Defining life poses a challenge that’s downright philosophical. There’s no ambiguity in looking for water, because we have a clear definition of it. That definition is the same whether you’re on Earth, on Mars, or in intergalactic space. It is the same whether you’re dealing with water as ice, liquid, or vapor. But there is no definition of life that’s universally agreed upon. When Portland State University biologist Radu Popa was working on a book about defining life, he decided to count up all the definitions that scientists have published in books and scientific journals. Some scientists define life as something capable of metabolism. Others make the capacity to evolve the key distinction. Popa gave up counting after about 300 definitions…

[Edward Trifanov, biologist at the University of Haifa] analyzed the linguistic structure of 150 definitions of life, grouping similar words into categories. He found that he could sum up what they all have in common in three words. Life, Trifonov declares, is simply self-reproduction with variations…

A number of the scientists who responded to Trifonov felt that his definition was missing one key feature or another, such as metabolism, a cell, or information. Eugene Koonin, a biologist at the National Center for Biotechnology Information, thinks that Trifonov’s definition is missing error correction. He argues that “self-reproduction with variation” is redundant, since the laws of thermodynamics ensure that error-free replication is impossible. “The problem is the exact opposite,” Koonin observes: if life replicates with too many errors, it stops replicating. He offers up an alternative: life requires “replications with an error rate below the sustainability threshold.”

Jack Szostak, a Nobel-prize winning Harvard biologist, simply rejects the search for any definition of life. “Attempts to define life are irrelevant to scientific efforts to understand the origin of life,” he writes…

It’s conceivable that Mars has Earth-like life, either because one planet infected the other, or because chemistry became biology along the same path on both of them. In either case, Curiosity may be able to do some good science when it arrives at Mars this summer. But if it’s something fundamentally different, even the most sophisticated machines may not be able to help us until we come to a decision about what we’re looking for in the first place.

I have to agree with Szostak; the definition of life is, at least from science’s perspective, irrelevant. However, there is a standard set of criteria used by biology, as far as I learned in school and Wikipedia has to say:

  • Homeostasis: Regulation of the internal environment to maintain a constant state; for example, electrolyte concentration or sweating to reduce temperature.
  • Organization: Being structurally composed of one or more cells, which are the basic units of life.
  • Metabolism: Transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
  • Growth: Maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
  • Adaptation: The ability to change over a period of time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism’s heredity as well as the composition of metabolized substances, and external factors present.
  • Response to stimuli: A response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion, for example, the leaves of a plant turning toward the sun (phototropism) and by chemotaxis.
  • Reproduction: The ability to produce new individual organisms, either asexually from a single parent organism, or sexually from two parent organisms.

Seems like pretty basic, inclusive criteria. Homeostasis is a word you don’t hear often, but it’s important; it’s basically what keeps organisms being themselves. It’s an organism’s negative feedback mechanisms, always adjusting to changes and trying to keep its state in the ideal place – ideal temperature, ideal CO2 level, ideal blood sugar, anything and everything. Also note that viruses aren’t considered to meet this definition of life; they can’t reproduce themselves per se, they’re not composed of cells, and they don’t grow, as far as I’m aware. 

Carl Zimmer posted a response to his article from an evolutionary biologist named David Hillis that I found interesting and insightful:

Like all historical entities (including other biological taxa), it is only sensible to “define” Life ostensively (by pointing to it, noting when and where it began, and following its lineages from there) rather than intensionally (using a list of characteristics). This applies to the taxon we call Life (hence capitalized, as a formal name). You could define a class concept called life (not a formal taxon), but then that concept would clearly differ from person to person (whereas it is much less problematic to note examples of the taxon Life). So, I’d say that I can point to and circumscribe Life, and that it the appropriate way to “define” any biological taxon. A list of its unique characteristics is then a diagnosis, rather than a definition. So, I’d argue that any intensional definition of Life is illogical (does not recognize the nature of Life), no matter how many words are used.

Defining Life (the taxon) is like defining other particular historical entities. We don’t “define” Carl Zimmer or the United States of America by listing out their attributes. Instead, we point to their origin and history. The same should be true for Life. If we ever discover a Life2, we’ll have a new origin and history to point to…

So that is another way of looking at it that I had never heard before, and it seems like the reasonable way to think about life. I don’t know if we’ll find any revolutionary kind of life in my lifetime, but if we do it’ll be pretty interesting to see different fields struggle with the implications. I hopefully will not be too worried about that – I’ll just want to pick its brains.

Genetically Engineered Silkworms Spin Super Strong Partly-Spider Silk

Scientists have taken a new step towards mass-producing spider silk, an incredible material whose potential we haven’t been able to harness quite yet. From Not Exactly Rocket Science:

Spider silk is a remarkable material, wonderfully adapted for trapping, crushing, climbing and more. It is extraordinarily strong and tough, while still being elastic enough to stretch several times its original length. Indeed, the toughest biological material ever found is the record-breaking silk of the Darwin’s bark spider. It’s 10 times tougher than Kevlar, and the basis of webs that can span rivers.

Because of its enticing properties, spider silk has enormous potential. It could be put to all sorts of uses, from strong sutures to artificial ligaments to body armour. That is, if only we could make enough of the stuff. Farming spiders is out of the question. They are territorial animals with a penchant for eating each other. It took 82 people, 4 years and 1 million large spiders to make a piece of cloth just 11 feet by 4 feet…

As a large industry and centuries of history can attest to, silkworms are easy to farm in large numbers. And they’re silk-spinning machines, with massive glands that turn silk proteins into fibres…

Fraser had just the right tool for the job. In the 1980s, he identified pieces of DNA that can hop around insect genomes, cutting themselves out of one location and pasting themselves in somewhere else. He named them PiggyBac, and he has turned them into tools for genetic engineering. You can load PiggyBac elements with the genes of your choice, and use them to insert those genes into a given genome. In this case, Florence Teulé and Yun-Gen Miao used PiggyBac to shove spider silk genes into the silk-making glands of silkworms…

These engineered silkworms produced composite fibres that were mostly their own silk, with just 2 to 5 percent spider silk woven among it. This tiny fraction was enough to transform the fibres. They were stronger, more elastic, and twice as tough as normal silkworm fibres. And even though they didn’t approach the strength and elasticity of true spider silk, they were almost just as tough…

The team are also planning to refine their technique to take the silkworms’ own proteins out of the equation. “The next step will be to produce silkworms that produce silk fibres consisting entirely of spider silk proteins,” says Jarvis. Perhaps they could even use the genes from the best of the silk-producers, like Darwin’s bark spider.

Seems like a promising approach; maybe commercial products using spider silk are in our not-too-distant future. Something tells me it won’t be marketed as “spider web” though, so I’m curious to see what companies will call it when they commercialize it. 

You can read about that 11×4 ft cloth made by farming actual spiders at Wired here; the process involved capturing a million spiders off of the street in Madagascar. I previously talked about an art project mixing spider silk and human skin, where the combination was strong enough to take a hit from a bullet at reduced speed. Cool things (not human spider cool, but other kinds of cool) are in our future.

New Species Discovered Near Antarctic Seafloor

A plethora of new species have been discovered around hydrothermal vents near Antarctica. As always, the ocean has many surprises for us.

From ScienceDaily:

‘Hydrothermal vents are home to animals found nowhere else on the planet that get their energy not from the Sun but from breaking down chemicals, such as hydrogen sulphide,’ said Professor Alex Rogers of Oxford University’s Department of Zoology, who led the research. ‘The first survey of these particular vents, in the Southern Ocean near Antarctica, has revealed a hot, dark, ‘lost world’ in which whole communities of previously unknown marine organisms thrive.’

Highlights from the ROV [Remotely Operated Vehicle] dives include images showing huge colonies of the new species of yeti crab, thought to dominate the Antarctic vent ecosystem, clustered around vent chimneys.

We heard about yeti crabs earlier, when we learned that one species of them off the coast off Costa Rica may farm bacteria on its claws by waving them over methane-seeping fissures to feed them, then chowing down. Obviously cold fissures by Costa Rica are very different from hydrothermal vents by Antarctica, but it would be awesome if we found that a species had the same strategy there.

Elsewhere the ROV spotted numbers of an undescribed predatory seastar with seven arms crawling across fields of stalked barnacles and found an unidentified pale octopus nearly 2,400 metres down on the seafloor.

A seastar is a starfish, something I did not know. A predatory seven-armed starfish sounds like a thing of nightmares – if you’re a tiny sea animal anyway.

‘What we didn’t find is almost as surprising as what we did,’ said Professor Rogers. ‘Many animals such as tubeworms, vent mussels, vent crabs, and vent shrimps, found in hydrothermal vents in the Pacific, Atlantic, and Indian Oceans, simply weren’t there.’

The team believe that the differences between the groups of animals found around the Antarctic vents and those found around vents elsewhere suggest that the Southern Ocean may act as a barrier to some vent animals. The unique species of the East Scotia Ridge also suggest that, globally, vent ecosystems may be much more diverse, and their interactions more complex, than previously thought…

‘These findings are yet more evidence of the precious diversity to be found throughout the world’s oceans,’ said Professor Rogers. ‘Everywhere we look, whether it is in the sunlit coral reefs of tropical waters or these Antarctic vents shrouded in eternal darkness, we find unique ecosystems that we need to understand and protect.’

Very cool, as always. Scientists who look for new ocean species must laugh at their terrestrial counterparts; it’s like exploring space versus exploring your backyard. But now the real question: how do these new species taste?

The Basic Human Tastes

Our society has traditionally recognized four tastes: sweet, salty, bitter and sour. In modern times however we’re better able to get to the root of taste, seeing what molecules are detected by our taste buds, and it has become apparent that there are more basic tastes than we once thought. The most well known one is umami, a savory taste, but LiveScience brings us some other candidates for basic tastes, excerpted below:

1. Calcium

The element calcium is critical in our bodies for muscle contraction, cellular communication and bone growth. Being able to sense it in our chow, therefore, would seem like a handy tool for survival.

Mice seem to have it figured out, kind of. Recent research has revealed that the rodents’ tongues have two taste receptors for calcium. One of those receptors has been found on the human tongue, though its role in directly tasting calcium is not yet settled, said Tordoff.

Calcium clearly has a taste, however, and counterintuitively most mice (and humans) don’t like it. People have described it as sort of bitter and chalky – even at very low concentrations. Tordoff thinks our calcium taste might actually exist to avoid consuming too much of it…

2. Kokumi

That calcium receptor might also have something to do with an unrelated sixth-taste candidate called kokumi, which translates as “mouthfulness” and “heartiness.” Kokumi has been promulgated by researchers from the same Japanese food company, Ajinomoto, who helped convince the taste world of the fifth basic taste, umami, a decade ago.

Ajinomoto scientists published a paper in early 2010 suggesting that certain compounds, including the amino acid L-histidine, glutathione in yeast extract and protamine in fish sperm, or milt – which, yes, they do eat in Japan, and elsewhere – interact with our tongue’s calcium receptors.

The result: an enhancement of flavors already in the mouth, or perhaps a certain richness. Braised, aged or slow-cooked foods supposedly contain greater levels of kokumi…

3. Piquance

Spicy-food lovers delight in that burn they feel on their tongues from peppers. Some Asian cultures consider this sensation a basic taste, known in English as piquance (from a French word). Historically, however, food scientists have not classified this undeniable oral sensation as a taste.

That’s because certain piquant compounds, such as capsaicin from peppers, directly activate our tongue’s touch, rather than taste-bud, receptors. The key piquancy receptor is called TRPV1, and it acts as a “molecular thermometer,” said John E. Hayes, a professor of food science at Penn State….

4. Coolness

At the opposite end of taste sensation from piquance’s peppers is that minty and fresh sensation from peppermint or menthol. The same trick of sensory perception is at work here – activated touch receptors, called TPRM8 in this case, fool the brain into sensing coldness at normal oral temperatures, said Hayes.

As touch sensations, both piquance and coolness are transmitted to the brain via the trigeminal nerve, rather than the three classical nerves for taste. “The set of nerves that carry the burn and cooling sensation are different than from taste sensation,” said Hayes.

Still, there is an argument that temperature sensation, both in the genuine sense and in the confused-brain phenomenon of piquance and coolness, deserves to be in the pantheon of basic tastes. Interestingly, Germanic people dating back to 1500 had considered heat sensation as a taste, Hayes said, and the modern debate over temperature’s status is far from over.

5. Metallicity

… Some Asian cultures place gold and silver leaf, as it’s called, atop curry dishes and candies, while Europeans fancy a bit of these metallic foils on pastries…

Although usually tasteless, such garnishes are sometimes reported as having a distinctive flavor. Researchers have shown that this sensation might have something to do with electrical conductivity, in effect giving the tongue a little zap…

Lab tests have failed to turn up a metallic-taste receptor, Lawless said, and it remains unclear if electrical conductivity or something more is going on for those shiny culinary embellishments. “We’re leaving the door open,” Lawless said.

6. Fat

The jury is still out on whether our tongues can taste fat, or just feel its creamy texture…

Mice can taste fat, research has shown, and it looks like humans can too, according to a 2010 study in the British Journal of Nutrition. The study revealed varying taste thresholds for fatty acids – the long chains that along with glycerol comprise fats, or lipids – in participants.

Intriguingly, the subjects with the higher sensitivities to fat ate fewer fatty menu items and were less likely to be overweight than those with low sensitivity…

7. Carbon Dioxide

Yet another strong sixth taste candidate: carbon dioxide (CO2). When dissolved in liquids, this gas gives soda, beer, champagne and other carbonated beverages their zingy fizz.

That familiar tingling was thought to result from bubbles bursting on the tongue, and had therefore been consigned to the touch category. “It’s tricky because CO2 was always considered a trigeminal stimulus,” said Tordoff.

Researchers presented a strong case for dedicated, taste bud-based carbon dioxide sensors in a Science paper in 2009. They found that an enzyme called carbonic anhydrase 4, which appears on sour taste-sensing cells, specifically detects carbon dioxide in mice…

Pretty interesting stuff. This is another scientific topic where it pays not to get emotionally attached to convention – the fact that there aren’t 5 senses or 9 planets or 4 tastes should be exciting new developments, not scary challenges to our worldview.

It’ll be interesting to see when our culture catches up to these realities; we already acknowledge foods as spicy or minty, but how long will it be before advertisers say their food is more umami or kokumi than their rivals’? 

Five Basic Human Psychological Flaws

In preparation for New Year’s resolutions, LiveScience put together a sort of advice column meets science article with five different scientists each discussing a basic psychological flaw that all humans share. As I’ve said before, I always find this kind of information extremely interesting since it’s something we tend to deny or ignore, when openly acknowledging our unavoidable biases would be the best way of overcoming them. So let’s acknowledge them here!

Check out the article at LiveScience for the full scoop, but here are some excerpts:

1. We Fear the Other

… Social psychologists call this “in-group” bias; cognitive psychologists see its advantages in fluent, speeded-up processing of the familiar. We’re long used to who we are, and so no real thought is necessary to deal with ourselves. Thus, in order to preserve our precious laziness of thought, we heavily invest in surrounding ourselves with people just like us. We segregate into neighborhoods and work and leisure environments where any others closely approximate us in age, race, income, political allegiance and even sexual orientation or the accepted type of facial hair.

The consequence is that we never get to meet anyone who isn’t like us. This, in turn, leads to failing to imagine any Other, and to a loss of desire to even consider the Other as someone who exists, a real human being just like us, except not just like us…

2. We Indulge in Ill-Informed Stereotypes

… I study the brain in love. My colleagues and I have put over 80 men and women into a brain scanner (MRI), and we found no gender differences in romantic passion. This Single in America study tells it like it is: Men are just as eager to find a partner, fall in love, commit long term and raise a family. And the sooner journalists (particularly those writing for women’s magazines), social scientists (particularly those convinced that men are evil), TV and radio talk-show hosts, and all the rest of humanity that berates men begin to embrace these findings, the faster we will find — and keep — the love we want.

3. We Go With Our Gut

The emerging view in psychology is that morality is something we feel more than think. Rather than reasoning our way to decide what is right and what is wrong, there is now overwhelming evidence to suggest that moral evaluations are “gut” reactions that we justify after the fact with what seem like principled arguments…

When victims of misfortune are close to us — when we can see and feel their suffering — we are capable of incredible generosity and self-sacrifice. When our connection to victims is less visceral, however, even when we “know” full well of their suffering in a cognitive sense, we are often unmoved by their plight and able to rationalize our inaction… Our tendency to mistake what we feel for what we think, especially in the realm of moral judgment and
decision-making, plays a central role in intergroup conflict and moral hypocrisy, and because the problem lies as much in our guts as in our minds, it is a challenging weakness to overcome…

4. We Lack Empathy

In my view, the most pervasive limitation in people is the ability to accurately understand the feelings and needs of others, and to fully appreciate their own impact on other people.

This ability is typically conceptualized in terms of “empathy,” “emotional intelligence,” “social intelligence” or “interpersonal intelligence,” and it clearly varies in strength from person to person.

While I think that people broadly recognize the value of this ability for selfish gain (e.g., to be an adept communicator, or to “charm” others), it also plays a critical role in caring for others — empathy most certainly does this in motivating altruistic behavior…

5. We Act Out of Self-Preservation

One of the most disturbing things I have learned about people is that they are very self-protective, sometimes at the expense of others. My research in sexual harassment demonstrates that people will blame others in a manner that protects their own interests. People who unconsciously find themselves to be similar to victims of sexual harassment will assign a relatively stronger level of blame to sexual harassers. This is not particularly disturbing; what is disturbing is that people who unconsciously find themselves to be similar to sexual harassers tend to let people off the hook for sexual harassment and even go so far to blame the victims of the harassment…

These are pretty simple things, as with many biases and fallacies; the notable thing with all of these problems is that we all have them, whether we realize it or not.

If you think about it, all of these issues come down to faults in critical thinking. As the third point notes, we allow ourselves to behave immorally by rationalizing our feelings instead of applying our moral framework to the facts of the case. If we practice putting feelings aside and instead dispassionately analyzing the facts in front of us, we can avoid every one of these issues. That kind of thinking is what makes science go round, so the more we practice thinking like scientists, the easier it may be to stick to our morals instead of our guts. 

“Ocean Bacteria Glow to Turn Themselves Into Bait”

Aaaand we’re back! I hope you had a lovely break, and that one of your new year’s resolutions was to read even more science! I’ve been off in the non-virtual world for the past week, but it is time to get back to business. And remember that for more science goodness you can follow Science Picks on Twitter at @SciencePicks, or if you’re Twitter-averse you can see the extra links I tweet on the sidebar to the right. 

Not Exactly Rocket Science has an interesting article on glowing ocean bacteria and why they do what they do, with a bit of an introduction here:

On 25 January 1995, the British merchant vessel SS Lima was sailing through the Indian Ocean when its crew noticed something odd. In the ship’s log, the captain wrote, “A whitish glow was observed on the horizon and, after 15 minutes of steaming, the ship was completely surrounded by a sea of milky-white color.” The eerie glow appeared to “cover the entire sea area, from horizon to horizon . . . and it appeared as though the ship was sailing over a field of snow or gliding over the clouds”. The ship took six hours to sail through it.

These glowing seas have featured in sailor stories for centuries. The crew of the Nautilius encountered the phenomenon in Jules Verne’s Twenty Thousand Leagues Under the Sea. And in 2006,  Steven Miller actually managed to recover satellite images of the very same patch seen by the crew of the SS Lima – it stretched over 15,000 square kilometres, the size of Connecticut or Yorkshire.

The glowing waters are the work of bioluminescent bacteria – microbes that can produce their own light. They are found throughout the oceans, although usually in smaller numbers than the giant bloom responsible for the SS Lima’s sighting. In many cases, they form partnerships with animals like fish and squid, taking up residence inside their hosts and paying their rent by providing light for navigation or defence.

But many glowing bacteria live freely in the open ocean, and they glow nonetheless. Creating light takes energy, and it’s not something that’s done needlessly. So why do the bacteria shine? One of the most common answers – and one that Miller proposed to explain his satellite images – is that the bacteria are screaming “Eat me!” at passing fish. A fish’s guts are full of nutrients, and it can carry bacteria across large distances. The bacteria, by turning themselves into glowing bait, get a lift and a meal.

The article goes on to explain a study that showed this in action: basically, zooplankton – a classification for small organisms that drift around in bodies of water – were given a choice of eating glowing or non-glowing bacteria, and they tended to choose the glowing bacteria. Presumably this is because the bacteria only glow when they’re grouped together, which happens when they find a tasty piece of detritus to hang onto. Glowing bacteria means there’s food around, so they’re a nice target.

As a side effect, organisms that eat glowing bacteria will sometimes end up glowing themselves, making them big targets for fish. A deadly circle of life, all so that some bacteria can hitch a ride. 

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