Field Guide to Super Powers

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The X-Man Wolverine has never been one of my favorites. Maybe it’s because it didn’t seem fair. Most mutants only get one ability, but he got two: an impossibly potent healing factor and retractable bone claws that are housed in his forearm. The latter seems to require the former or he would run the risk of infection and severe loss of blood every time he popped his claws out.

frog

Wolverine (c) Marvel Comics, artwork by Frank Miller. Image: Gustavocarra / Creative Commons License

In terms of a “healing factor,” The Field Guide to Super-Powers is replete with examples.  Most of us are familiar with reptiles and amphibians that can regenerate lost tails and limbs. There’s even a newt (Notophthalmus viridescans) that can regenerate a lost an eye, for Pete’s sake. We’ll discuss some choice invertebrates below that also regenerate bits and pieces they’ve lost. So, healing factor identified in nature. Check. Let’s turn our attention to those ridiculous…er…fascinating claws.

lizardOuch. Photo (c) Gary Nafis

Wolverine’s bony claws are housed in his forearm and pop out of his knuckles. As an added bonus, some really bad people coated the claws and all of his bones with unbreakable adamantium so these babies can cut through anything. What makes the ability particularly strange (and I realize we left strange behind some time ago, but bear with me) is that it requires Wolverine to do some self-inflicted damage since those claws must pierce his skin each time they are deployed. Obviously, he can handle it since he has the healing factor. But surely self-inflicted wounds don’t happen in nature, right?

cucumberYeah, I used the cartoon before. So what? It’s mine! (c) Jay Hosler

In fact, there are a number of examples of critters that will do bodily harm to themselves if the circumstances are dire enough. Sea cucumbers will eviscerate themselves and sea stars will jettison an arm to evade predators. Both, of course, can regenerate what was lost, so these are extreme but survivable, measures. They are also dependent on their respective “healing factors.” Now I know what you’re saying: These are last ditch defensive measures. Surely, SURELY, routinely popping bones out of your skin as a weapon makes no sense at all in nature.

Except, of course, it does, when it provides a selective advantage. Case in point: African frogs of the genera Astylosternus and Trichobatrachus. I spotted these creatures as I was wandering around Cameroon (O.K., David Blackburn made the actually discovery, but I did stumble across this as I was browsing through an old National Geographic a couple of weeks ago in my easy chair). When disturbed, these frogs deploy a bony claw from the tip of its toe. The claw is usually held in place by a stationary claw rest. To use it, a tendon pulls the claw from its resting position and the tip of the curved bone pierces the skin. Snikt!

x-frogs_claw_close_upPhoto (c) David Blackburn, Art by Mariel Furlong, National Geographic staff

A bad attitude seems to come along with claws like these (it probably stings a little for the frog and Wolverine).  When disturbed, these frogs apparently flip out, kicking and squirming in an attempt to inflict as many gashes as possible on their attacker. As the researchers who described this adaptation point out in Biology Letters, this is a truly unique adaptation. No other vertebrate has to pierce its own skin to use its claws.* Fortunately, the self-inflicted wound that results from their use is probably no big deal for the frogs since, like many amphibians, they do have that remarkable ability to regenerate tissues.

References
Blackburn, D.C. , Hanken, J and Jenkins Jr., F.A. (2008) Concealed weapons: erectile claws in African frogs. Biol. Lett. 4, 355–357

National Geographic (June 2009), Wildlife, page 22

* This is a unique claw, but other amphibians pierce their skin with other bones. When threatened, the ribbed newt Pleurodeles waltl can project poison-tipped ribs from their back.

Is there anything more unnerving than the thought of a shape-shifter in our midst? Imagine consummate infiltrators that can gain our confidence and then turn on us. There are several comic book characters with the ability to beguile others with false forms. Let’s consider a classic example. In the second issue of The Fantastic Four (1961), it appears as if our heroes have turned against humanity. The Thing uses his incredible strength to tear down a Texas oil rig, The Invisible Woman disappears with a diamond, the Human Torch melts a priceless statue and Mr. Fantastic uses his elastic powers and super brain to turn off all of the power in New York.

What the heck?

Of course, by page four we discover that the fantastic foursome is being impersonated by a band of shape-shifting aliens called Skrulls.

skrulltransformationThe Fantastic Four, Mr. Fantastic and Skrulls (c) Marvel Comics and created by Jack Kirby and Stan Lee

To bad no one else knows. The newspapers have declared the Fantastic Four to be Public Enemies and our heroes have to spend the next 18 pages clearing their name, saving the planet, hypnotizing the Skrulls into thinking they are cows and putting them to pasture.  Brilliant!

cows(c) Marvel Comics and created by Jack Kirby and Stan Lee

The Thing’s line in the final panel above is prophetic. There was, indeed, worse trouble ahead.  In 2008,  47 years after the Skrulls first appeared, they were the villains in a major comic event called Secret Invasion which involved them…uh…secretly invading Earth. I didn’t read it, but apparently it did NOT end with all the Skrulls being transformed into grazing ungulates, so it couldn’t have been that good.

A whole host of other shape-shifting characters can be found in the various pantheons of four-color, spandex–wrapped power fantasies, but can any be found in nature? (Rhetorical question.) There are, of course, organisms whose shapes are meant to deceive us. Take these insects that look like sticks and leaves.

InsectMimicsA mantis that looks like a stick and butterfly that looks like a leaf. Awesome sauce!

This really is spectacular, but these critters are stuck with this particular form.  We’re looking for shape-shifters. Are there any in nature that can change to look completely different? (Again, rhetorical.)  Some, like the chameleon, can adaptively change their color to blend in with their surroundings. This is an effective means of hiding from predators and sneaking up of prey, but they haven’t changed shape. A chameleon may be hard to spot, but if we do spot him we can easily identify him as a chameleon.  We want something that can change shape and color, like the green-skinned Skrulls. Hmm. We would need something that is smart, profoundly flexible and capable of quick color changes.

Sounds like an octopus to me.

The mimic octopus is the king-cat-daddy of shape shifting. But it does something more that just look like another creature, it acts like the organism it is mimicking. This has always been the downfall of many evil shape-shifters. Sure they can look just like your dear old pal, but can they act like her? Behavioral and physical mimicry make this a truly impressive critter.

Stunning. But what happens if we expand our definition of ‘shape?’ Being visual creatures we obviously associate the identity of something by what we can see. But, for many critters vision isn’t the primary means of identifying individuals, smell is.

Consider the rove beetle Atemeles pubicollis. These little rascals look nothing like ants.  Yet, despite the lack of resemblance, the ants will treat this rove and its offspring like one of their own.  A. pubicollis infiltrates the nests of Formica polyctena and proceeds to lays its eggs there. For most insects, this would be a good way to get your babies eaten by ants. But the rove beetle larvae release an ant pheromone that tricks its hosts into thinking the beetle is family. The beetle larvae then proceed to gobble up the ant larvae with whom they are sharing a crib. They even have the hutzpah to beg for more food from the adult ants. To do so, they tap the ants mouthparts with their own to get a sugary sweet desert. When the larvae metamorphose into grown-up rove beetles, they continue to live in the nest and solicit food from the adult. Diabolical!

rovebeetle

The rove beetle is certainly Skrull-like in its ability to infiltrate and exploit, but it lacks the plasticity of a true shape-shifter because it’s stuck with one olfactory ‘shape’

That isn’t a problem for the bolas spider.

Bolas spiders eat male moths as they fly about at night looking for love.  Male moth find females not by seeing them (it is night, after all) but smelling them. Females that are receptive to mating release a pheromone perfume to announce they’re on the market. Not surprisingly, these odors are species specific since you wouldn’t want a male codling moth trying to hook up with a female greater peacock moth (gross!).  Thus, each night the air is full of specific perfume signals and the bolas spider can mimic many of them.  Using an arsenal of odors, the bolas spider sends alluring calls to males of many species who soon discover that they are looking for love in all the wrong places. She changes her olfactory shape by changing perfumes. The result is a chilling bit of olfactory shape-shifting. See for yourself.

The bolas spider’s odor mimicry is an amazing bit of chemical chicanery that should make us all paranoid. After all, who nose who you can trust?

_________________________________

References

1. Holldobler, B. (1971) Communication between ants and their guests. Scientific American 224 (Mar): 86-95

2. The rove beetle figure and figure caption was taken from Alcock’s Animal Behavior (5th edition). I believe the drawing originally appeared in reference 1, but I need to check that.

3.  Stowe, M.K., Tumlinson,J.H. and Heath, R.R. (1987) Chemical Mimicry: Bolas Spiders Emit Components of Moth Prey Species Sex Pheromones. Science, 236: 964-966

4.  Bolas spider clip from David Attenborough’s Life in the Undergrowth (via Youtube)

There are a handful of idioms relating to human explosions and most aren’t good. You can get so angry you blow your top, your plans can blow-up in your face and you can only bottle-up your frustration for so long before you explode. These are metaphorical eruptions but there are a handful of comic characters that do have the ability to go ka-blooey as part of their modus operandi. Perhaps most famously, is the super villain Nitro, the Living Bomb, who can blow himself to atoms and then reassemble himself. He pulled this stunt a few years ago outside a school and precipitated a Civil War in the Marvel Universe.

NitroCovers

Nitro lords it over Captain Marvel and blows-up Iron Man. All three are (c) Marvel Comics

This, of course, works as a super power as long as you can put yourself back together, but if you can’t, blowing yourself-up is a done-in-one kind of stunt. As Daffy Duck demonstrates in the clip below, the results can be spectacular…

…but it’s only good for one round of applause. Given that nature lacks a live studio audience, what would motivate a critter to self-detonate? The answer, of course, is the greater good!

Ants are social insects that live in colonies. They’re tremendously successful organisms and display a wide variety of fascinating physical and behavioral adaptations. There are farmers, soldiers, workers, architects and even ants that act as food storage units. In each ant colony a single queen lives with millions of her offspring. However, only the queen can reproduce. Why would her kids give up the ability to make babies and pass their genes onto the next generation? Many behavioral biologists think that by working to ensure the survival of their bothers and sisters, worker ants are also promoting the survival of copies of their genes into the next generation. This, for ants, may be the greater good. In that context, it’s not that surprising to find ant species with a number of bizarre, self-sacrificing adaptations, including self-detonation.

CamponotusAntCamponotus saundersi

The world of ants is a violent one. Colonies routinely seek each other out and fight territorial wars that result in devastating carnage. The Malaysian ant Camponotus saunderi will mix it up with the best of them and, if the battle should start to take an ugly turn, they will blow themselves up. To understand how, lets consider a unique aspect of their anatomy.

CSaundersiGlandsDiagram of Camponotus saundersi highlighting her absurdly large mandibular glands in blue. Modified from Maschwitz and Maschwitz, 1974.

Most ants have glands in their head associated with their mandibles, the big pinching mouthparts that ants use for cutting and chewing their food. In many ants, including C. saundersi, these mandibular glands secrete alarm chemicals that alert the colony to danger in the same way the smell of smoke might alert you to the possibility of a fire nearby. Unlike most ants, however, the mandibular glands of C. saundersi are enormous, extending from the animal’s mouth, through the thorax and into the abdomen. They are also full of sticky goo. If worse comes to worse, and the battling C. saundersi have no other choice, they violently contract the muscles of their abdomen and squeeze their mandibular glands until they pop out of their body and explode into a spray of enemy-immobilizing glue.

camponotuscartoon

Unlike Nitro, C. saundersi cannot reassemble themselves afterward. But, if they can turn the tide on their enemies they may make it possible for their genes to live on in the sisters and brothers they saved. At the very least, they go out with a bang.

Beautiful sounds like the rhapsodic strings in an orchestra or the melody of a song bird can be stunning. Not surprisingly, several comic characters take this metaphor and make it reality (as real as comics can be, that is). The crime fighter Black Canary can produce a cry from her super vocal chords that can break things, knock people out and, as an absolute last resort, put the kibosh on them completely. Fellow good guy and physician Dr. Mid-Nite has determined that Black Canary’s cry reaches into the ultrasonic range. This, according to him, is what spells lights out for the bad guys. From this diagnosis we can derive only one, inescapable conclusion: Dr. Mid-Nite is a quack.

BC finalBlack Canary (c) DC Comics

Humans can’t hear ultrasound and as a consequence shouldn’t be affected by it. Imagine how awful it would be if we were. Every summer barbeque would have to wrap up at dusk so that the intense ultrasonic cries of echolocating bats didn’t make us pass-out on our sizzling grills and impale ourselves on our croquet wickets. No, it is clear that the good doctor got it wrong. Fortunately, scientists in this dimension have identified a few critters that can incapacitate (and kill) with sound. Enter the snapping shrimp.

snapping shrimpSnapping shrimp. Note the big right claw. Figure from Versluis, et al. (2000) Science 289, 2114

The snapping shrimp is about the size of half a hot dog and it has one claw that is much bigger than the other (see image above). When the snapping shrimp leaps into battle it puts the hurt on its foes by snapping it’s big claw ridiculously fast. As the claw closes during a snap, it shoots out a jet of water. No big deal, right? Every kid at the pool can do that. But this jet of water moves faster than the surrounding water can rush in to replace it and a bubble of air stretches out in its wake. But the gas in this bubble (called a cavitation bubble) is extremely thin and it rapidly collapses under the pressure of the surrounding water. When this happens, the collapsing water produces a high-pressure sonic pulse that can stun or even kill a small fish within 4 cm.

snapping shrimp 2

Time lapse of cavitation bubble formation and change in sound pressure. Figure from Versluis, et al. (2000) Science 289, 2114

During time lapse footage of  the snapping shrimp closing its claw you can see the formation of the cavitation bubble (a couple of frames after the frame labeled 2 in the figure above) and it’s collapse (the frame labeled 3). The graph on the left shows the peak in sound pressure that corresponds with the collapse at 3. In other words: Ka-Pow! The sound created by the snapping shrimp is audible and a reef with a lot of snapping shrimp can sound like the shootout at the O.K. Corral. This might explain the snapping shrimp’s other moniker: the pistol shrimp. Hmmm. One animal, two names. Kinda sounds like a secret identity. I can see the comic book tag line now:

The Stunning Pistol Shrimp, Stopping Crime is Snap!

snappingshrimp_small

Versluis, M, Schmitz, B,  von der Heydt, A and Lohse, D (2000) How Snapping Shrimp Snap: Through Cavitating Bubbles. Science 289, 2114

Like many super-heroes, Daredevil has a suitably tragic origin. As a boy, Matt Murdock was hit by a truck carrying radioactive waste. The accident left him blind and accentuated his senses. It also gave him a “radar sense” that allows him to detect objects around him. This ability was originally described as being similar to echolocation, but that was later changed to be more of proximity detector. It was good change.

Organisms like bats that use echolocation emit ultrasonic calls and then listen for the echo. By comparing how long it takes for the echo to return they can determine how far away an object in the environment is, the closer the object the sooner the echo returns. Daredevil does not, however, emit any noise when using this power.

MillerRadar

Artwork by Frank Miller. Daredevil (c) Marvel Comics

Daredevil can sense animate and inanimate objects in the environment all around him (including behind him) and he can do so in the dark.  His life depends on his ability to sense a pointed gun or a raised knife. In today’s episode we will discuss a knife that can do the same thing.

knifefishThe weakly electric knife fish (photo credit unknown)

The knife fish found in Africa’s Black Volta River lives in water so murky that, like Daredevil, it is essentially blind. So how does it navigate the rocks and roots of the river, find food and avoid predators? The knife fish generates an electric field around its body. This is a weak field and can’t deliver a high voltage shock like an electric eel. However, the fish can detect anything that enters the field. Here’s how.

EOD-largeThe Electric Organ.(figure from PLoS Biology, 2009;7(9): e1000203 DOI: 10.1371/journal.pbio.1000203))

The fish has an organ called the electric organ in it’s tail. The electric organ is highly modified muscle tissue that generates electrical pulses that travel out from its tail and around to the front of the animal. If something enters the knife fish’s electric field it disrupts the flow of these electrical waves and the fish becomes aware of the intruder.  Very cool, but it gets better. The fish can tell the difference between an inanimate object and something living based on how much the electrical waves are deflected.

Weakly electricFigure taken from Eckert’s Animal Physiology (4th ed.). It is originally from “Electric Location in Fish” by H.W. Lissman(c) 1963 Scientific America, Inc.

Nonliving materials (like a rock or a rubber tube) tend not to conduct electricity very well. This means they force the fish’s electrical waves to take a big detour one the way from the electric organ to the head. Living things, on the other hand, are full of salt water and are good conductors of electricity, so they only disrupt the knife fish’s electric field a little bit because they conduct the fish’s electrical waves better than the rock (see the image above).

The catch to this is that weakly electric fields only work for critters surrounded by in water. That’s bad news for Daredevil, but great news for anyone who might one day get hit by a nuclear submarine that had a leaky reactor.

In this episode of The Field Guide to Super Power we celebrate the coming of spring by taking a parting look at the ice that is melting all around us. There are a number of super-powered characters out there that hang their hat on the ice motif. Let’s consider Marvel Comics’ Bobby Drake, aka Iceman.

Iceman_Marvel_Value_Stamp

Iceman copyright Marvel Comics

Iceman is a mutant whose super human biology allows him to turn to his body into solid ice, shoot frozen projectiles from his hands and zip around on the icy slides he makes (for some animated Iceman see this clip from the classic Spider-Man and his Amazing Friends).  For most of us, freezing any part of our body would destroy cells, lead to frost bite, necrosis and potentially amputation. Being frozen solid would kill us. But for some critters, turning into a popscicle is just part of the yearly cycle.  Consider the weta, Hemideina maori, a flightless insect that lives above the tree line in the mountains of New Zealand’s southern island.

wetaHemideina maori: image copyright of Maria Minor and Alastair Robertson (Massey University)

Life above the tree line can get pretty nippy in the wintertime (it’s also quite brisk in the summer, I imagine) and most critters run the risk of being put on ice, literally. This can be particularly bad for insects because unlike mammals and birds, they don’t generate their own body heat and are usually the same temperature as the environment. So how does the weta avoid freezing to death? By freezing, of course.

The big problem with freezing living tissue is that when ice forms inside a cell, it expands and rips the cell apart. That’s bad.  Hemideina maori eludes the icy finger of death with molecules called ice nucleators that are circulating in their blood-like hemolymph. Like seeding a cloud for rain, these ice nucleators promote the formation of ice crystals in the fluid outside the weta’s cells. As this ice forms, most of the cells’ water gets sucked out and frozen in the hemolymph. Thus, no ice forms inside the weta’s cell and the cellular machinery doesn’t get shreaded. When the weta warms up, its internal ice thaws and flows back into its cell.

Hemidiena maori can actually survive after 82% of the water in its body turns to ice. Considering that animals are mostly water, this means most of the critter is frozen solid just like Iceman. The weta can survive in this frozen state for up to 8 hours at -8C but if the temperature dips a little lower to -9C they can only make it for 5. They’re goners if the mercury hits -10C.

FrozenCapThe Avengers, Captain America and all of this other stuff is copyright Marvel Comics. Artwork by Jack Kirby

The freeze tolerance of the weta may also shed light on a related comic book mystery. While on a mission near the end of World War II, Captain America was cast into the frigid Artic waters where he was frozen in an iceberg and remained in suspended animation until he was thawed out in Avengers #4. How would this be possible? Perhaps, the super soldier formula that transformed puny Steve Rogers into the Captain America had some heretofore unknown ice nucleating properties.

Wouldn’t that be cool?

As super-powers go, living forever isn’t one of the flashiest nor is it all that original to the comic book genre. That said, there have been a number of memorable comic book characters that have immortality. The DC villain Vandal Savage was a caveman whose exposure to a radioactive meteorite made him an immortal jerk.  He’s spent the last 50, 000 years trying to take over the world.

Savage

Vandal Savage (c) DC Comics, Mr. Immortal (c) Marvel Comics

On the other end of the serious spectrum, you have Marvel Comic’s goofy Mr. Immortal, the good-guy leader of the whimsical Great Lakes Avengers. He’s a mutant who can’t be killed but it isn’t entirely clear how he survives his fatal injuries. Where exactly is the immortality gene in humans? Nowhere, that’s where. However, there may be a biological explanation for immortality that we can torturously extract from the biology of a hydrozoan jellyfish. Let’s start by taking a look at its life cycle.

Hydrozoa_Life_cycle

Colonial hydrozoan life cycle

When adult hydrozoan jellyfish (known as a medusa) aren’t busy stinging the bejillikers out of humans at the beach, they are busy floating in the ocean stinging the bejillikers out of small copepods and eating them. It’s a good life, but eventually the time comes to make babies. At this point, male and female jellyfish release eggs and sperm and then promptly expire. Meanwhile, the egg and sperm unite to form small, free-swimming planula larvae. The planula larvae settle on the ocean floor where they metamorphosize into a colonial polyp. The polyp is the juvenile stage and it looks like an inverted jellyfish, with tentacles sticking up rather than hanging down.

In this stage, the polyp can asexually create numerous small, jellyfish adults. This alone is quite a trick. In most cases (like you, for example), when a single egg fuses with a single sperm a single individual is formed. In the hydrozoan jellyfish, one sperm and egg can lead to a multitude of adult individuals because of the polyp’s prodigious cloning capacity.

Okay, now, for the immortal part. The adult jellyfish Turritopsis nutricula has found a way to cheat death.

jelly_cartoon_02

After reproducing (and before expiring), Turritopsis nutricula shift their lifecycle into reverse and revert to the immature polyp stage. For this to happen, all of the adult cells have to revert into juvenile cells. The process of one type of specialized cell turning into another is called transdifferentiation and it usually only happens when some creatures regenerate organs. No other critter uses this trick to pull a Ponce de Leon and switch back into a kid. With the ability to transition back and forth between adult and polyp there is no limit to Turritopsis nutricula’s potential lifespan, because the adult stage need never die. And, even if some of the adult Turritopsis nutricula do die (perhaps eaten by some sea slug that will steal their stings), a zillion of their clones will endure elsewhere.

Turritopsis-nutricula-3

Turritopsis nutricula

In fact, this jellyfish seems to have been using this remarkable super-power to avoid death and spread silently from its native Caribbean waters. Turritopsis nutricula has been popping up in oceans all over the globe, slowly inexorable taking over the world.

Vandal Savage would be proud.

Further reading:

Bavestrello, G. Sommer, C., and Sará, M. 1992. Bi-directional conversion in Turritopsis nutricula. In Aspects of Hydrozoan Biology. (J. Bouillon et al., editors). Sci. Mar. 56 (2-3): 137-140.

Piraino, S., Boero, F., Aeschbach, B., and Schmid, V. 1996. Reversing the life cycle: Medusae transforming into polyps and cell transdifferentiation in Turritopsis nutricula (Cnidaria, Hydrozoa). Biol. Bull. 90: 302-312.

Super powers seem to fall into two broad categories: those that emulate what other organisms do naturally (like scaling a shear wall or breathing under water) and those that do not (such as shooting beams of energy out of your eyes or becoming intangible). The power to steal someone else’s powers, as Superman’s nemesis The Parasite can do, always seemed to fit squarely in the latter category. A recent discover in sea slugs, however, suggests that power stealing may have a natural analog.

SeaSlugscartoon (c) Jay Hosler 2010

In the comics, the Parasite can absorb the super powers of any hero he touches. Tap the Flash on the shoulder and he gets super speed. Shake Superman’s hand, and he’s able to leap tall buildings in a single bound. Nudibanch sea slugs appear to have a surprising similar ability.  Researchers have identified a species of sea slug, Elysia chlorotica , that steals chloroplast from algae and then starts photosynthesizing. The nudibranch takes a single meal of algae early in life, extracts the chloroplasts from its prey and inserts them into its cells.

This ability to harvest the cellular apparatus of another species seems to be something nudibranchs do very well. Several species of nudibranchs have been identified that can extract the stinging organelles (or cnidocytes) of jellyfish and coral and insert them into their own tissues for protection (although, how they extract the sensitive cnidocytes without triggering them is a still a mystery).  But, just like the Parasite, this ability doesn’t last forever.  Once the nudibranch has fired its purloined cnidocytes, it must replenish them by eating more jellyfish or coral.

What makes the discovery of Elysia chlorotica so exciting is that, unlike the Parasite or its cnidocyte-stealing nudibranch brethren, once E. chlorotica has the ability to photosynthesize it never loses it. And it never eats algae again. This is surprising because the stolen chloroplasts require a constant supply of chlorophyll to catch the light necessary for photosynthesis. But if the sea slug isn’t eating algae then it can’t replenish the chlorophyll that way. It would have to make its own, and we know of no animal on the planet that can do that. Until now.

E. chlorotica has the genetic hardware to make it’s own chlorophyll and keep its stolen chloroplast running. Where did it get the genes to do this? Probably stolen from some algae a long time ago.

The research was published in the Nov 18, 2008 issue of Proceedings of the National Academy of Sciences