Mantis shrimp's punch, and low-methane rice
In this week's Naked Scientists Podcast: Uncovering the secret behind the mantis shrimp's giant punch. Also, developing a new strain of rice that produces a fraction of the methane, and shaking virus particles to hear their song. Plus, we profile NASA's new chief, Jared Isaacman...
In this episode
01:05 - How mantis shrimps stun prey without knocking themselves out
How mantis shrimps stun prey without knocking themselves out
Graham McShane, University of Cambridge
The mantis shrimp is well-known for packing a gigantic punch. It’s so powerful, in fact, that they’re able to smash the shell of a prey animal with the force of a sledgehammer swung at full pelt. But if it’s socking its opponent sufficiently hard to knock it into next week, why doesn’t the shrimp knock itself out in the process? Somehow it seems to be able to shield itself from the force, and now scientists in the United States have sussed out how: it’s all down to the cleverly evolved structure of the shrimp’s “club”, which can dampen the shockwaves so they don’t propagate back into the animal’s body. Graham McShane is a fellow at Queens’ College, Cambridge, where he works on artificial structures just like these. I asked him for his thoughts on the study…
Graham - So, what they've been looking at is this mantis shrimp which has this adapted leg, this dactyl club that it uses to attack its prey. And it's got remarkable features because it strikes the prey with this club with such force, the force is a thousand times the weight of this little shrimp. And the question is, well how does this shrimp attack its prey in this way without injuring itself? And it can attack its prey hundreds and hundreds of times with this club but not injure itself.
And so what the researchers were trying to understand is: what are the mechanisms at play here that allows this material to behave in such a way? Because if we can understand the mechanisms we can design materials with these properties for our own use.
Chris - I suppose in some respects Newton's third law says, if I hit you really hard I feel the same pain that you do because the same force is coming back into me. So, how does the shrimp exert that huge force and the force coming back not then knock out the shrimp?
Graham - Absolutely. So, the shrimp has got this very clever design of its club where it can almost spring load its club to sort of launch it at its prey and it strikes the prey with tremendous force. And as you say that then sends a huge shock wave back through the club and into the shrimp. And the question is how does the shrimp dissipate that or how does the design of the club dissipate that? And I think researchers have been aware of a couple of different mechanisms for a while and so they've understood that the architecture of this club is such that it avoids the club shattering.
It's an incredibly hard, incredibly tough material and they've looked at the structure of it and they've realised it's got this hierarchical structure. It's made up of these fibers of biopolymer which are then grouped together in bundles and then these bundles are themselves grouped together in layers and then these layers are then stacked on top of each other in different arrangements. And they've understood that that's what gives this club its incredible toughness because cracks don't propagate very easily through that material so that avoids the club shattering.
But in this latest study they're also thinking about the shock wave that travels through that club. So, how does that shock wave then not injure the shrimp? And what they've realised is that the architecture of this material of this club is able to dissipate the energy of that shock in a very effective way. It's called an acoustic metamaterial.
It can manipulate the way waves propagate through it using this architecture of the material and they've developed some very clever experiments to really try to study this effect and to understand what's going on as these shock waves propagate through the material and then how they're dissipated at this microstructural level.
Chris - I was just going to ask that. These small vibrations are incredibly fast so how are they actually watching what happens inside this creature's club as it uses it?
Graham - They're using very clever techniques with lasers. So they're using lasers which they're reflecting off the surface of the material and they can use that to excite the material.
The lasers can locally heat the material which can cause elastic waves to propagate through the material and then they can use a similar technique to look at how the material is responding. They're able to take very fine measurements at very small scales to measure essentially the sound waves as they're propagating through the material and study how they're reflected and how they're dissipated within the material and that gives them the data that they need to understand these mechanisms.
Chris - Is it effectively then a baseball bat but with a really good shock absorbing handle? So, I can hit someone really hard with it not that I would and what comes back up my arm is a fraction of the force that hits the person very hard and knocks them out?
Graham - Absolutely right and so what's going on is if you imagine the handle of that baseball bat has got a very clever microstructure like the one I described, such that when the shock wave tries to propagate through the handle it reflects internally in complicated ways around this microstructure and those internal reflections can cancel each other out and they can dissipate and so the shock wave is blunted and that energy is absorbed so that you never feel it in your hands, and so it's a very clever way of dissipating that shock so it doesn't injure the mantis or you holding your baseball bat.
Chris - Can we use this because it sounds to me like there are a lot of different possible applications now we understand how this is working? can we steal it basically?
Graham - Absolutely. So, there are a huge number of applications where we can use this kind of thing. We can think about protective equipment, so helmets, body armour where sometimes it's not enough to just stop something that's hitting you, you also need to deal with the shock wave that propagates through as a result as well and dissipate that. We could come up with clever ways of designing liners for helmets as well as very tough and hard surfaces that will stop projectiles and so on. We could think about protection of buildings, so protecting buildings against shocks and earthquakes absorbing the energy of those shock waves without causing fragmentation and damage of the buildings. Crash protection for vehicles, protection, shock protection for sensitive things like sensitive equipment, batteries, electronics and so on. We can look at nature and we can learn from the mechanisms that are at play and also the way nature combines lots of different functions together in a single material. We can learn from that to create effective and efficient materials. The challenge for us is understanding those mechanisms and then understanding how we can fabricate materials that deliver those mechanisms on an engineering basis.
07:23 - Low-methane rice to reduce emissions
Low-methane rice to reduce emissions
Anna Schnurer, Swedish University of Agricultural Sciences...
Now here’s a powerful statistic for you: over half the planet’s population depend on rice for the majority of their calories; but current rice cultivation, in turn, is responsible for 12 per cent of global methane emissions, and these emissions are expected to increase with global warming and a rise in the human population. Now, scientists have identified chemical compounds released by rice roots that drive the production of that methane. This information enabled them to breed a new, high-yielding strain of rice, by crossing the non-methane emitting variety with an existing crop rice, to produce a form of the plant that doesn’t release these chemicals and consequently emits up to 70% less methane. I’ve been speaking with Anna Schnürer, a biologist at the Swedish University of Agricultural Sciences…
Anna - Rice cultivation leads to a lot of methane and methane is a very strong climate gas, so by growing a lot of rice, because we also need food for the growing human population, we actually create a problem with a lot of methane going out to the atmosphere.
Chris - Is the methane produced by the rice plant or is it produced by the conditions the rice is growing in?
Anna - So, it's not produced by the rice plant itself, but the rice plant helps because the rice plant releases different types of chemicals around the roots and these compounds can be used by different microorganisms in the soil and as a result we get methane that is produced.
Chris - So, the rice is making the problem happen, but it's because it's feeding the wrong sort of microbes effectively?
Anna - Yes, exactly. So, our approach has been to try to understand more exactly what is released from the roots of the rice plants and in what way these compounds feed the microbes. So, there is a collaboration between the rice plant and the roots and the microbes.
They are helping each other, so to say. So, it's a good thing that you have microorganisms in the soil around the roots, but we don't want the wrong microorganisms to grow.
Chris - How did you track that then to work out what it was that the rice was releasing that feeds the microbes that then turns into methane?
Anna - We had two different types of rice plants, one that had a low emission of methane and one that had quite high emissions and then we compared these two plants. So, we did a chemical analysis of the compounds that were released from the plants to try to see if there was a difference between them and if there is a difference, what is the actual compound that differs between these two rice? And in doing so, we could actually detect the compound that was specifically linked to the methane production.
Chris - Ah, right. And so the form of rice that doesn't produce as much methane produces less of these compounds from its roots?
Anna - Yes. So there is an organic compound called fumarate and this organic compound is used by the microbes as food and then it's converted into methane, which is then released from the rice fields.
Chris - And does the rice have to get rid of that fumarate in order to be healthy? So when you compare these two rice plants, the one that does and the one that doesn't make methane, is the one that doesn't produce methane from its roots less healthy or is it perfectly happy and the yield is the same?
Anna - Yeah, it's actually perfectly happy because it's not only this fumarate that is released, it's a lot of different types of compounds and all these different compounds are food for the microbes in the soil. But fumarate is very specifically linked to the microbes that are releasing the methane.
Chris - Given that you've got a form of rice then that doesn't produce much methane, have you solved the problem? Do we just grow that everywhere or is that just a laboratory specimen that's good in some respects for studying but it's not a high yielding variety we could feed the world with?
Anna - Yeah, this rice is actually a high yielding variety. So, what we have done is that we found this low methane emitting rice and then we have crossbred it with a high yielding variety to have a rice that has both low methane and high yield. So, this new variety that we have produced can actually give us both more food and at the same time reduce the amount of methane.
Chris - Brilliant. Is this now it then? It's a slam dunk. We're in a position where you can take this rice that you've bred and it should be capable of growing in all the different rice growing environments around the world or is it fussy? Will it need further adaptation?
Anna - You can grow it in many different areas but it can't tolerate all different types of temperature areas. So we still need to continue to breed for more similar rice varieties that can grow under different temperature conditions. So this rice can be used in many areas but not all. So, not the tropical regions for example.
Chris - Is the next step then to take some of those tropical cultivars and cross them with your low methane variety, going for one that has the ability to tolerate the tropics but still doesn't churn out loads of methane?
Anna - Yes, exactly.
Chris - And is that hard to do?
Anna: No, not now I would say because we know the mechanism. We know what we are searching for. So I think this is not a complicated thing to do now.
Chris - And so if you were able to get this across the world, something like half the world's population depends on rice, doesn't it? The impact would be huge.
Anna - Yes, rice cultivation today represents a lot of the methane that is released into the atmosphere and it's also increasing because the temperature is increasing. So it's like a bad loop that's going on right now. We need more food, more rice and the temperature is already going up and that's also increasing the activity of these methane producing organisms in the soil. So this is a problem that we really need to take care of.
What does a virus sound like?
Elad Harel, Michigan State University
It might seem like a strange question - but it’s one that scientists have been attempting to grapple with in a bid to find out whether we can better defend ourselves against them, and also gain new insights into how they operate inside cells. Elad Harel at Michigan State University has got a way to shake virus particles with lasers and then “listen” to the vibrations to work out what shapes they are and what they’re made of. It’s amazing…
Elad - We wanted to know if we could track a virus by its sound. Do viruses make a sound? Can you induce them to make a sound?If they do, can we use that to track them and avoid some of the challenges with studying them nowadays?
Chris - They're also, some of them, one thirty thousandth of a millimetre across. Absolutely tiny. How on earth can you listen to something that small?
Elad - We've looked at very small objects before. We've looked at the nanoscale; a billionth of a metre. And we knew that we could measure these kinds of vibrations, we call them acoustic vibrations. We could do it on these metal nanoparticles. But from a very naive point of view, a virus is a small nanoparticle. It's very well organised and well structured. And we thought maybe it also produces some kind of ordered vibrations. We wanted to know if we could pick that up. We knew approximately where we would be looking.
It's about a frequency that's a million times higher than what humans can hear. It's something that you need very specialised instrumentation to detect. And the challenge really was the fact that a virus is embedded in a very complex environment. If you think about the virus in a cell, there are lots of other materials around it. And all of these materials also give rise to different sounds. So, could we pick up the sound in the background of everything else? Trying to pick up the sound of, say, an insect in a forest from hundreds of metres away. That was the technical challenge that we were facing.
Chris - How did you do it then? What was the apparatus that enabled you to tune in to the sound of a virus?
Elad - What was really amazing was that we could use light both to generate the sound and to detect the sound. So you can think of light as a hammer. Like when you bang on the table with a hammer, you bang on the nail, you're banging on the wall, you're really causing vibrations in that material. All those atoms that are in that material, in that table, in that wall, in that piece of glass, whatever it may be, they're all vibrating. So what we did is we used light as the hammer itself. So the light actually caused this virus particle to vibrate at this very, very high frequency.
And then to detect that, we used another laser pulse, which actually scattered off the vibrating virus particle. We capture this in a kind of stroboscopic way. So, that means that if you've ever been to a disco - or to a club - and you see that strobe light, right, and it kind of flashes on and off and you see these snapshots of people moving, that's kind of the idea where we hit this thing with a hammer, it starts vibrating, and then we wait a little bit of time, we take a picture of it. And then we repeat that over and over again, about 100 million times a second. And we build up a kind of a movie that shows a sound wave that goes up and down, up and down. This virus is really acting like a very small instrument.
Chris - Just out of interest, what virus was it that you were using as your test virus here?
Elad - It was a rhinovirus.
Chris - So, the common cold, the thing that every one of us is suffering with. Did you get it from someone in the lab?
Elad - We got it from a collaborator.
Chris - What, from his own nose? Or what I meant was, did someone donate the specimen of their own mucus because it's so common, isn't it? But more seriously, what is the purpose of this? Is it just that you're stressing the system to prove that you can do this with these tiny entities? Or is it that there may well be an application to being able to probe tissue that's got things like viruses lurking in it like this?
Elad - We see it as having two main applications. On one hand, diagnostics. You can imagine, with PCR tests, you can't detect whether the virus infection is active or not because the virus may have already ruptured and you're detecting really the genetic material inside of the virus. So here we have a method where we can detect the virus at the single virus level. That's just one virus particle. So we have the ultimate limit of sensitivity. And so you could imagine detecting viruses very, very early on before the onset of any symptoms. And because you could do it with light, you could even do it at a distance without making any physical contact.
On the other hand, we're primarily interested in the applications, understanding how viruses actually function. What are the dynamics of viruses? How does a virus assemble? How does a virus disassemble? How does a virus attach to a receptor? How does it get brought into the cell? If you can track that in real time, which is what we're trying to do now, you could develop antivirals by targeting any part of the virus life cycle to really speed up and streamline that process of trying to understand how drugs interrupt the binding or some other process where viruses can replicate and can infect you and make you sick.
20:12 - Trump's NASA pick: Jared Isaacman
Trump's NASA pick: Jared Isaacman
Richard Hollingham, Space Boffins
The US space agency NASA has been in a state of flux for a number of years, and it now has to compete with a number of private companies who are seeking to challenge its dominance. It also now has a new boss, because, traditionally, the director is replaced by an incoming president. And Donald Trump’s pick for NASA chief, Jared Isaacman, has raised a few eyebrows. Isaacman doesn’t have any NASA experience. But, he has got lots of money, he has worked with some of the major new players in the US space industry, and he has been into space. I asked Richard Hollingham from the Space Boffins Podcast to tell us more about him…
Richard - Oh, he's fascinating. Well, he's another tech billionaire and he was born in 1983. He created his first tech company at 15. It's a payment processing company. He then branched out into a defence company that trains US Air Force pilots. He's got a passion for flying. He's got a passion for spaceflight. He led the first private space mission. He took part in the first private spacewalk. In fact, as an astronaut, he has gone higher - or that crew went higher - than any astronaut since the Apollo missions of 1972. So as an astronaut and as an astronaut pioneer, he has certainly got the right stuff, if you like, for doing that. It does sound uniquely well qualified, actually, for this job.
Well, he's probably uniquely well qualified to push forward astronauts, human space flight missions to the moon, missions to Mars. But NASA is so much more than that because, of course, it does exploration missions like the amazing James Webb Space Telescope that's giving us these just stunning images of the most distant galaxies and also our own planets. It also has a lot of Earth observation missions.
So giving us that sort of eye on the planet and what's going on. So NASA is lots more than that. It also has a whole flight division where they're looking into innovations in flight. So, for example, NASA developed fly-by-wire technology, which is in every aircraft. So, NASA is a lot bigger than just sending astronauts to the moon and Mars.
Chris - But he is a pilot, isn't he?
Richard - Absolutely.
Chris - I mean, he flies stunts at air shows and things. He flies jets.
Richard - And it's not a surprise that he's been nominated to become the new head of NASA by Donald Trump. I was listening to his inauguration speech and I said, "What?" He just mentioned Mars. I had to spool back and hear that again. Donald Trump said: "we will put an American on Mars."
That is not the current NASA plan. The current NASA plan is to return humans to the moon and have the first woman on the moon. Straight away there, you've got something very different in the offing.
Chris - He also said, that's Donald Trump, he said: "Jared will drive NASA's mission of discovery and inspiration, paving the way for groundbreaking achievements in space science, technology and exploration." I mean, that does sound on message. So what are the people who are objecting to this saying then? What's the controversy?
Richard - Very few people have actually said that he's the wrong person, because you could argue that the former head of NASA, Bill Nelson, is almost the equivalent of a private astronaut. So Bill Nelson had flown in the space shuttle, but as a congressman, as a politician on the space shuttle. And I can't tell you, I can't really share with you what some of his crew members said about him at the time, but the shuttle crews very much considered these politicians in space as self-loading cargo, if you like, on these missions. It's always a political appointment, the head of NASA.
Chris - So, do you think then that because he's run very successful companies and is a tech billionaire, but doesn't necessarily have yet the political experience, that that might be something that people are saying is a weakness, because he's got to go and deal with politicians?
Richard - Yeah. So you've got these, the billionaires, or the millionaires, if you like, you've got Donald Trump talking about going to Mars, you've got Elon Musk, developing these incredible, spacecraft and Starship, which is the one that's currently in development, that he wants to take people to Mars. You've got Isaacman, you've also got, don't forget, Jeff Bezos, who has developed the New Glenn rocket as well, which is going to give Musk and SpaceX a run for their money.
And then you’ve got in the other corner, the NASA way of doing things, which takes a lot longer, but also involves a lot of people, and a lot of people who are often in Republican areas. So, you know, particularly with the current plan to send people to the moon is to use a brand new rocket called the SLS, Space Launch System. A giant rocket, looks very much like a sort of mashup between the Apollo, Saturn V rocket and the Space Shuttle. So, it's a big rocket, a big tube with two solid boosters on the side. This has been developed in Huntsville, Alabama, Republican territory. So you've got that.
So, if you start taking that away, if you start saying, well, the SLS isn't really going to do it, let's use Starship instead, which would make a lot of sense, there is going to be a political backlash to that. So, it's got to be handled carefully, but the SLS, it just looks so old fashioned compared to what Elon Musk is developing and what Jeff Bezos is developing, that inevitably, even if they fly the ones they've built, they probably won't build any more. So, that's the old way of doing it. And now you've got the new way of doing it, which Jared Isaacman very much represents.
26:32 - Are bone conduction headphones safer?
Are bone conduction headphones safer?
Bill writes in to ask whether his bone conduction headphones are dangerous to his hearing. James Tytko enlisted the help of audiologist Roger Lewin to find out...
James - Thanks Bill. When paying attention to sound in the environment, or when listening to the Naked Scientists Podcast through traditional headphones, sound waves are being funneled through your outer ear to the ear drum, causing it to vibrate. The vibrations are amplified by three tiny bones in the middle ear, and eventually reach the cochlea, a spiral-shaped organ in which the movement of fluid stimulates tiny hair cells, converting mechanical vibrations into electrical signals which our brain can interpret.
But what about your bone conduction headphones? How do they work, and do they pose a risk to our hearing in the same way as headphones that sit in or on our ears might? To help us with the answer, I’ve been speaking with audiologist at the Knutsford Hearing Centre, Roger Lewin…
Roger - Thanks James. Bone conduction headphones work by converting sound into vibrations that are transmitted through your skull - typically via your cheekbones - directly to your cochlea. The skull is a dense, solid structure, which makes it an excellent medium for bone conduction, though it affects sound differently compared to air conduction. This process bypasses the outer and middle ear and has enabled people who have problems in these areas, those with issues like ear infections, malformations, or fluid buildup for example, to hear better.
They’re also popular with people like yourself Bill who like to listen to things through headphones without giving up the sounds of the natural environment, as they sit just in front of the ears on the cheek bones and don’t block sounds taking the conventional route through our auditory system.
James - Beethoven famously used a primitive form of bone conduction as his hearing deteriorated, biting down on a rod placed against his piano to hear the sound it was producing.
But what about the risks posed to our hearing from bone conduction headphones?
Roger - Noise-induced hearing loss occurs when intense sound damages the delicate hair cells in the cochlea in the inner ear. The powerful vibrations created by loud sounds may overstimulate the hair cells, bending them too far or too frequently. If hair cells become damaged due to repeated, intense exposure, they will not regenerate like other cells in the body, and this can lead to permanent hearing loss.
While bone conduction headphones are enabling sound to bypas your outer and middle ear, they are still relying on the cochlea to translate sound vibrations into electrical impulses, and so you should still take care. Most commercially available headphones are designed with ear safety in mind, but you should adhere to the warnings from your smartphone if they’re detecting high exposure.
James - So Bill, make sure you’re taking good care of your ears by limiting your exposure to loud noises for long durations, as bone conduction headphones do have the potential to cause damage to the cochlea in your inner ear. Thanks to audiologist Roger Lewin for helping us with that one.
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