Caterpillars kings of the mimics

Scientists from Oxford and Turin have found that certain species of caterpillars have developed the ability to use sounds to fool ants into accepting and nurturing them.

Writing in this week's Science Francesca Barbero and her colleagues describe how they used sensitive microphones to eavesdrop on Myrmica schencki ants, the nests of which are invaded by caterpillars of the rare blue butterfly Maculinea rebeli.  Somehow these caterpillars persuade the ants not just to accept them but also to treat them like royalty, even feeding their own young to the hungry butterfly larvae if food runs short.

Scientists have known for some time that chemicals come into play and that the caterpillars secrete odour molecules that make them smell like an ant, but that couldn't be the whole story because it wouldn't explain why the larvae receive such preferential treatment in the nest.  This prompted the Oxford and Italian team to wonder whether the caterpillars might also be resorting to a form of sonic subterfuge to elevate their status because the ants communicate with one another through rasping sounds produced by rubbing together the rough surfaces of parts of their abdomens.

Queen ants produce subtly different sounds to workers, and recordings from the caterpillars in the nests show that they are mimicking the noises of ant queens.

"This is the first time anyone has been able to record like this, with insects in their native environment and that are not distressed.  This is why we picked this up," explains co-author Jeremy Thomas.  "This is a wonderful example of evolution.  This blue butterfly group has a long history of a co-existence with this ant species.  Over time the caterpillars have adapted to exploit the ants by mimicking their signals, allowing the caterpillar to penetrate the nest where the ants protect and feed it."

8th Feb 2009

Nemo could get lost in acidic ocean

If you’ve seen the movie Finding Nemo, then you’ll know that Nemo the clown fish got lost and had to try and find his way back to his home reef.

Now it seems that the Disney animators may have been onto something, because a study published in the journal PNAS led by Philip Munday from James Cook University in Queensland, Australia, found that clown fish may indeed get lost if the oceans become more acidic. And that is likely to happen as more carbon dioxide enters the atmosphere and dissolves in the seas forming carbonic acid.

Many coral reef fish spend the first few weeks of life as tiny larvae drifting through the open ocean. And previous studies have shown that they follow their noses and their ears, sniffing out and listening to sounds that lead them back to the reefs they were born on.

But, it seems that as the acidity of seawater increases, fish may loose their sense of smell and have trouble finding their way home.

Munday and his team took newly-hatched clown fish larvae and put them in choice chambers in the laboratory filled with water containing different chemicals. In seawater of normal acidity, the clownfish preferred to swim in the plume of water that smelt of rainforest trees, because in the wild they live on reefs that surround vegetated islands.

When the acidity was increased, the clown fish instead choose to swim in the plume of water that smelled of swamps, a smell they hate and usually avoid.

It may not sound like much of a difference – swamps or rainforest trees - but if wild fish start to loose their ability to find the right sort of habitat, it could spell disaster for entire populations and ecosystems.

So this study spells out yet more gloomy forecasts for the changes that might take place as carbon dioxide continues to build up in the atmosphere and even more reason to try and find ways of curbing our emissions of the greenhouse gas.

8th Feb 2009

Gravity may make sea level rise worse

If the world is going to warm up then this is going to cause the sea level to rise. As water warms up it expands so it takes up more space and as ice on the continents melts it dumps more water into the oceans. Many models predict the melting of the west antarctic ice sheet which is predicted to produce a 5m rise in sea level, but researchers from the university of Toronto have noticed that these models haven't taken something important into account.

And that's gravity. Everything with mass attracts everything else with mass gravitationally. So the 22 million billion tonnes of ice in the ice sheet are attracting the sea water around them. This lifts the local sea level creating a bulge around the ice sheet. So when the ice sheet melts you not only get a redistribution of the water in the sheetbut around it too. Also moving around thousands of cubic kilometers of water could cause the earth's axis to move by as much as five hundred metres which will move where the centrifugal bulge of the earth is acting changing the shape of the earth and the oceans above it.

The overall effect of all this is that the sea level aroung north america and the southern indian ocean could rise an extra 1.5m on top of the 5m already predicted and the sea around west antarctica could only rise 4m instead of 5.

8th Feb 2009

A new urine test for heart disease

This week researchers have reported a new way of diagnosing whether someone is likely to develop coronary artery disease or CAD by testing the chemicals present in their urine.

CAD is a major cause of death around the world and currently the only way to diagnose it is to conduct an angiogram, which is expensive and invasive involving injecting dye into the blood that shows up on x-rays and allows doctors to see how badly blood vessels are getting lined by fatty deposits or plaque, that can restrict and eventually block the flow of blood to the heart causing a heart attack.

Now a team of researchers led by Karlheinze Peter from the Baker Heart Research Institute in Melbourne, Australia have identified 17 specific peptides (the molecules that make up proteins) in the urine of people who were diagnosed as having CAD using angiograms.

Their study published in the Journal of proteome research describes also describes how Peter and his team carried out a blind test on these peptides. By first screening the urine of a group of volunteers, then subsequently giving them angiograms it was shown that the urine test accurately picked out the people with CAD around 84% of the time.

They also found a direct link between these peptides and CAD, because they found these same chemicals in the fatty plaques that line the blood vessels of people with the condition, which is presumably why these peptides are finding their way via the blood stream into the urine.

It is still early days for a new CAD urine test to be rolled out, but these findings point the way towards a cheap, non-invasive test, that one day may hopefully help to detect the condition much earlier, giving patients a chance to make changes to their diet and lifestyle to help control the development of the disease.

8th Feb 2009

Finding the Oldest Evidence of Life

Chris - Researchers have found evidence of the earliest animal life on Earth.  It shows that complex life was actually flourishing here much earlier in the Earth’s history than we previously thought.  Dr Gordon Love who’s at the University of California at Riverside has covered the chemical fingerprints of sponges which are thought to be the first forms of animal life.  He found it in rocks that are up to 750-odd million years old.  Hello, Gordon.  Welcome to the Naked Scientists.  What have you actually done?

Gordon - What we did was we looked through rocks in a certain line and we have a continuous sequence of rocks and an opportunity for looking at the geobiology of this time.  We found a continuous 100 million year record of sponges, going from a time known as the Cryogenian which is the time associated with two immediate glacial episodes and extending right up into the early Cambrian period.

Chris - Where did you get these rocks from?  How did you find them?

Gordon - We were fortunate we were working with an oil company in Oman, Petroleum Development in Oman.  They’re just currently in an area of the world where people are producing vast amounts of oil from rocks of this age.  Through our contacts in the oil company we had access to very pristine material from drill cores.  That became very important in having this stretch of time and also the fact that these were very thermally well-preserved rocks that we were dealing with.

Chris - If you’re looking at the fossil record though, and this frustrated Charles Darwin, life appears to pop into existence about 540 million years ago because prior to then presumably there weren’t enough animals with hard body parts that could be fossilised.  You’ve presumably run into the same problem.  How do you know you’ve got sponges going back 750 million years?

Gordon - These are one of a number of steroid structures that we detected.  The precursor to these molecules, the sterols are very specific to a class of sponge called demosponges.  Sponges make a wide range of really unusual natural products which really interest the medical field as well.  But in this case despite about four decades of research precursors have never cropped up.  These precursors have never cropped up in single-celled organisms.

Chris - So what you’re saying is you’ve now been able to unlock from the rocks chemical finger prints, if you like; molecules made by those early sponges 750 million years ago that when the animals died were locked away in those rocks.  Although the animals, the vestiges of them, physically are gone their chemical legacy lives on and that is what you can detect.

Gordon - Yes, I think that’s right.  This is an important factor that Darwin was puzzled about.  The lack of information is that if you look at smaller and smaller scale then there is a tangible record for animals significantly pre-dating the Cambrian explosion.

Chris - Just tell us a bit about the technique to get these molecules out of the rocks.  You get your rock sequence from the oil driller.  How do you then get out of the rocks the chemicals from the sponges?  How do you know which rocks they’ve come from and that they were actually made by the early sponges all that time ago?

Gordon - We’ve a couple of approaches.  The conventional way in organic geochemistry is to powder the rock after you’ve cleaned or removed the outer parts.  Do some sort of solvent extraction technique, concentrated up the steroid components in the fraction and analyse these by gas chromatography/mass spectrometry.  We found a really abundant amount of these steroids and in all the different rock formations that we looked at.  To confirm that we were actually, it wasn’t just coming from migrated oils that reside in the younger part of the section, what we did was we isolated what is an organic polymer.  The bulk of sedimentary organic matter is actually insoluble and it can’t migrate anywhere and they make up a large macromolecule.  We basically broke chemical bonds by using a technique where we heat up samples with high hydrogen gas pressure.  When we looked again at the steroid composition we saw that again these sterols were abundant products.  In that way we could more confidently equate the age of the markers with the age of the rocks with uranium-lead isotope dating.

Chris - So this shows you that those rocks of that age had complex animals like sponges living in them.  Why do you think that they’re there?  What does this tell us about the origin of animal life around on Earth at that time?

Gordon - Yes, most of the rock is in a depositional environment that we’re looking at is shallow, marine waters.  I think originally the simplest animals like sponges would have colonised the sea floor on a shallow continental shelf.  It could have been tens of millions of years later we thought they could pervade into deeper water environments.  I think it’s telling us that at this time in terms of the environment there was finite levels of dissolved oxygen near the sea floor – at least on the shallowest water environments.

Chris - Does it fit with what we understand was happening elsewhere on earth at the time?  Usually when you see an explosion of some evolutionary process there’s something going on in the climate or in the Earth’s other processes.  Can you marry this observation with anything else going on at the same time that might explain what you’re seeing?

Gordon - Yeah, now we’ve pushed this back, the first appearance, into the time frame of two vast glaciation events.  My feeling on this is I go to many rocks of age which are older than the first glacial event and I have never seen any convincing evidence for sponge biomarkers.  I think that these major glacial events radically altered ocean chemistry in the aftermath by shutting down a lot of obscure interaction.  It seems, although we’re still trying to get a handle on how exactly the chemical composition changed it seems they opened up avenues for new niches, especially for new organisms which could filter feed on the sea floor.

February 2009

Microwaving Ice - why defrosting is so slow.

It's "On Your Marks..." for a watery microwave race - will water boil before ice melts?...

What you need

What to Do

What may Happen

Although it only takes an increase of a few °C to melt the ice, and the water has to heat up by about 80°C to boil, the water will normally boil before the ice melts!

What is going on?

There are two effects happening here, one of them is that to melt ice takes a huge amount of energy, the equivalent of heating water by about 80°C.  This is because in ice water molecules are locked together by quite strong hydrogen bonds, and to melt it has to break a lot of these bonds, which takes a lot of energy.

The second effect is that ice just doesn't absorb microwaves nearly as well as water - this means it actually heats up less.

Why does water absorb microwaves better than ice?

A microwave oven cooks by creating microwaves, a form of light or electromagnetic radiation.  These are produced on the right hand side of the oven and are sent into the main oven.  They reflect back and forth creating a standing wave.

In the microwave the electric field will point upwards and then downwards about 2.5 billion times every second.  This means that anything charged will be pulled upwards and downwards by the field produced by the microwaves.

Although water molecules don't have an overall charge, their oxygen atom is slightly negative and their hydrogen atoms are slightly positive (they have a positive and negative pole so are called polar).  This means that in an electric field they will rotate to align with the field.

If the field keeps changing at 2.5 billion times a second they will keep rotating which will give them energy so the water heats up.

In ice the water molecules are all locked together in a crystal structure by hydrogen bonds.  These bonds will stop the water molecules rotating, which means they can't absorb much energy from the microwaves.  This, in turn, means that the ice doesn't heat up.

This is why you shouldn't defrost a chicken on full power.  As soon as some of the frozen chicken melts, the water it contains will be in the form of liquid water - which will absorb microwaves far better than the surrounding frozen water.  This means you will end up with part of your chicken fully cooked while the rest is frozen, and your meal will be horrid, if not dangerous!

The defrost setting on microwaves gets around this by by only heating for a few seconds every minute and essentially waiting for the hot bits of your chicken to melt their neighbouring areas.

What is a hydrogen bond?

The slightly negative oxygen of one water molecule will attract the slightly positive hydrogen from another.  This attraction will pull the molecules together and forms what is known as a hydrogen bond.

Written by Dave Ansell

The Future of Home Electronics

Meera - It’s time to find out what the world of technology has to offer in 2009. This month I’m in the business centre for BBC news online. I’m here with our resident tech expert, Chris Vallance.

Chris V - Hi, there’s a reason why we’ve come up here. That’s so  I can pick the brains of the BBC’s resident tech expert, Mark Ward who is the technology correspondent for the news website. We’re going to chat about trends in technology. It’s the start of the year. There’s one event which really showcases the tech industry: CES - the Consumer Electronics Show and Mark, you were there. It was at the beginning of January that the big conference happened. What was being showcased?

Mark - Lots of things, really. It’s a consumer electronics show. The clue’s in the title. Everything was there. The big surprise was that I was expecting lots of funky shiny stuff but the big thing there was TV. Bigger screens, obviously but more stuff to do with your big, flat panel TV you bought last year. It’s be either adding web bits to it or doing more with your high-definition movies and things like that. TV was the star of the show.

Chris V - And it was a bit 1950s as well, 3D TV?

Mark - Yeah. This was very much the kind of next generation, stereoscopic so you still have to wear a better quality of 3D. The problem is that, for all the talk you’re still going to have to buy a 3D capable set. That’s going to be pricy and there’s very little content out there at the moment. Broadcasters will when there’s content and the content makers will say we’ll make it when there’s an audience. At the moment it’s a lot of plans but precious little action.

Chris V - We have seen things like IMAX which have a similar problem. We have a huge cinema, you need special cameras. They have taken off so it’s not hopeless for 3D TV.

Mark - No, there’s a lot of commitment in the film industry to do it. In 5 or 10 years time we might start to see that percolate through but people keep their TVs for a long time. If you’ve just bought one you’re not going to spend the same amount again just to get 100 movies. There’s a vast catalogue of better stuff you could get at.

Chris V - I think for 2008 I’ve got in my hands one of these little tiny netbooks, these small very ultraportable laptops. They’re not very expensive and they’ve been a real hit. Is that going to continue next year, at least according to the people at CES?

Mark - Yes, there’s a lot of tiny, shiny computers on show. Netbooks now are about 50% of the PC market. Improved by 100% last year, probably going to do the same this year. I think at CES we saw the end of the compromises you’re going to have to make when you buy one. Typically it means they’re a bti slow. Graphics aren’t great and batteries can be a bit problematic. Whereas at the show last year we saw battery lives, much more powerful processors and graphics were starting to improve as well. You might be able to play decent  games on it and certainly show some video.

Chris V - But times are hard. Is that affecting what was on display at CES?

Mark - Well definitely. There  was certainly some stats quoted about sales figures, things like that. In certain sectors you’re starting to see a shift from the kind of maximum people can afford in terms of a flat panel TV to something they’re happy to spend. You see a bulge around the 32-40 inch sets rather than bigger than that. Certainly a lot of people were saying the consumers might hold up pretty well, actually. People have tended to have got their flat panel TV, got their games console, got their smartphone and now they want to do something with it. Games, movies, those kind of web-based services will be pretty popular over the next year as people stay at home rather than go out and save money.

Meera - mark, other than what you saw at CES this year is there anything else you’re looking forward to in particular?

Mark - There’s a growing emphasison green computers, green electronics, that kind of thing. I think Groucho Marx said about Doris Day – he knew her before she was a virgin. I suspect that’s the same with a lot of electronics companies. They discovered they’re not as bad in the green statistics as they thought. They’re touting that as something that people should pay attention to. I think people are pretty sceptical. I think it’s starting to figure in people’s perceptions beyond brand and price. People are going to start taking those green credentials quite seriously.

Meera - What about you, Chris? What do think’s coming up this year?

Chris V - I’m interested in, it’s not necessarily brand-new for this year, I think we’re going to see more of it and people employing this technology creatively. I’m interested in these SLR, single lens reflex, cameras that can shoot video. There are two on the market at the moment at very different price ranges. The films that they produce are really interesting because you can change lenses which you can’t do with a cheap consumer camera. You can put wide angle lenses, zoom lenses, you can even do those tilt-shift lenses to make everybody look like little tiny people. The creative possibilities are really interesting. The quality of images, because of the different way they focus onto the sensor, that looks very different as well. It’s more like film. There are drawbacks. People who’ve reviewed them have said they’re hard to handle, hard to keep them steady. You need tripods, you need to know what you’re doing. I think the creative possibilities are really interesting high-definition films produced on these things start to appear on the web. I’m just really interested. I want to see what people make with this stuff. It’s quite exciting from a visual point of view.

February 2009