The Naked Scientists explore the chemical link between asthma and eczema that has been uncovered; how a synaesthesia gene has been found; why rising levels of CO2 are affecting clown fishes' sense of smell; the evidence of a 700-million-year-old sponge which sets the clock back on evolution; how the butterfly species, Maculinea rebeli, convinces ants to look after their caterpillars; how IVF can help disentangle the effects of nature from nuture.
Plus in 'Stuff and Non-Science', can you predict a child’s adult height by doubling their height at 2 years?
Chris Smith: Coming up this week, how researchers drilling for oil actually struck fossil gold when they discovered evidence for the earliest animal life on earth.
Kat Arney: These are steroid chemicals produced by very, very primitive ancient sponges called demosponges. These were thought to be one of the very, very earliest forms of animal life. Now they find very high levels of these C-30 sterols in an area called the South Oman Salt Basin, this is at the south eastern tip of Arabia, so it certainly suggests that these animals in the form of these little wee sponges were around much earlier than we previously thought.
Chris Smith: Kat Arney who’ll be explaining later why we’re all related to a 700-million-year-old sponge. I think I’ve got a few of those lurking in my bathroom. Also on the way, the amazing story of a species of caterpillar that relies on ants to bring it up as one of their own.
Jeremy Thomas: We’ve been looking at some very rare butterflies that live as caterpillars and chrysalises inside ants’ nests. They live there for up to two years, and we’ve been looking at how they actually succeed in living in ants’ nests and exploiting all the resources inside an ants’ nest without being killed by the ants themselves.
Chris Smith: So how do these caterpillars fool the ants into thinking they’re one of them. We’ll be finding out from Jeremy Thomas later in the programme. Plus, in this week’s ‘Stuff and Non-Science’, how tall will your children be when they grow up. We’ll be finding out whether certain methods of predicting adult heights actually stand up to scrutiny.
Hello, I’m Chris Smith, welcome to Breaking Science which is produced in association with the Open University. First up this week and with news of fish lost at sea, the earliest animal life on earth, and why some people see colours whenever they hear certain words, here’s Kat Arney who’s also itching to tell us how scientists have uncovered a chemical link between asthma and eczema.
Kat Arney: Yes, more and more of us are suffering from allergies, including allergic asthma and a condition called atopic dermatitis, which is where the skin overreacts to common substances that are around us. And this is a condition that affects between one in ten and one in five children at the moment. But until now, although doctors had known these two were linked, it wasn’t clear molecularly how they were, but new results from researchers in France and Japan have now found a molecule that makes a connection between these two conditions.
Chris Smith: And what have they discovered?
Kat Arney: Well the scientists led by Zhikun Zhang triggered atopic dermatitis in mice by rubbing their ears with a chemical called MC-903, and this brings on an irritation and it activates a protein called thymic stromal lymphopoietin, which is also known as TSLP, in the skin cells.
Now the team discovered that producing this protein in the skin made the animals much more susceptible to developing a mouse version of asthma later in life and, when they tested these mice with allergens that bring on asthma, the mice who had developed atopic dermatitis when they gave them this chemical, were also much more likely to have inflammation in their lungs than mice that had never been treated with the chemical and had never developed the dermatitis.
Chris Smith: So how does this chemical that they’re rubbing onto the skin not only trigger the skin irritation but also make asthma happen at a totally different part of the body?
Kat Arney: Well the chemical is just what triggers the dermatitis and the dermatitis leads to the production of this protein called TSLP, and the scientists think that TSLP is being produced by the skin cells at the site of the dermatitis, but then it moves round the body in the bloodstream and aggravates the already overactive immune response that leads to the asthma.
Chris Smith: So where do they want to go from here, do they want to see if the same thing is true in humans?
Kat Arney: Well now this link has been found it does help us to understand more about the molecules that underpin these conditions, so if we can show that this is the same in humans maybe we could identify children who are at higher risk of developing asthma later in life.
Chris Smith: Although having said that, not everyone who has eczema, the atopic dermatitis, also gets asthma do they, so there has to be something more complicated going on, but I guess this is a good place to start.
Kat Arney: Exactly. It’s a good indication and it is the first molecular link that’s been found.
Chris Smith: Now talking about genes and how they’re linked to different conditions, there’s one very exciting condition which I’ve always wished I had just to be able to experience it, and that’s synaesthesia, the mixing of the sense, and scientists now reckon they’ve got one of the genes for that.
Kat Arney: Yes. Synaesthesia is a really fascinating neurological condition and it manifests itself in a range of ways. And it’s reasonably rare, it affects fewer than one in a hundred people, and it’s really described as if the sensory wires were crossed in your brain.
So for example, people with synaesthesia can smell colours or taste sounds, and now researchers in London, Cambridge and Oxford have tracked down specific regions of the genome that harbour genes that are linked to audiovisual synaesthesia. And we do know from previous research that this condition can run in families but researchers haven’t been able to pinpoint the genes that might be involved. But now writing in the American Journal of Human Genetics, Dr Julian Asher and his team used new genome scanning technology to hunt for genes that were linked to synaesthesia, and they used 43 families that had this condition in the family.
Chris Smith: And what have they actually found in those families?
Kat Arney: Well so far they’ve found four regions of the genome that are linked to synaesthesia. These were on human chromosomes 2, 5, 6 and 12. Now they haven’t found specific genes, they’ve just tracked down some general regions, and the regional chromosome 2 is probably the most intriguing, as it’s also been linked to autism and people with autism often have differences in their perception and their senses.
Chris Smith: But in what they did find, was there anything of interest in there?
Kat Arney: Well of the regions that they did find there are some very interesting genes in there, such as genes for epilepsy, genes that have been linked to dyslexia, learning and memory in some of these regions which obviously need a lot more investigation. And so far, although they haven’t found any specific genes there’s a lot of candidates which we could look at in future.
Chris Smith: As they say, nature normally reveals her workings through her mistakes because it gives us an insight into the molecular clockwork of how things like the brain actually work.
Kat Arney: Absolutely.
Chris Smith: Now turning to the sea, did you go and see ‘Finding Nemo’ when it was on?
Kat Arney: I have seen ‘Finding Nemo’, it’s a very sweet film, yes. And it features clown fish. Now clown fish are actually in the news today. You know, they’ve been made famous in the film ‘Finding Nemo’, but actually poor little clown fish do have a very rough life. They’re hatched as tiny little fry and they spend weeks drifting about in the sea trying to find their way home to the reef where they hatched.
Chris Smith: So that’s a very impressive and epic journey, but what do we know about how they do that though, how do they find their way home?
Kat Arney: Well baby clown fish rely on a range of signals to help them get home. Obviously they don’t have maps, they’re fish, but the most useful of these is their sense of smell. Now baby clown fish have very sensitive noses, they can detect tiny concentrations of smelly molecules, but sadly there is bad news for these little clown fish because rising levels of carbon dioxide could be throwing off their sense of direction.
Chris Smith: Why?
Kat Arney: Well there’s work done now by Philip Munday and his team from James Cooke University in Australia, and they’ve found that increasing the levels of carbon dioxide in seawater confuses baby clown fishes’ sense of smell and it sends them in the wrong direction.
Now to show this, the researchers grew up clown fish in a tank in the lab, then they put them in a tank with two channels in it, so can you imagine something shaped like a Y, and one arm of the Y was filled with water carrying a specific smell and the other arm contained just plain old seawater, so the fish could choose which they’d rather swim into. Now the researchers found that clown fish larvae would swim towards the channel that smelt of sea anemones or tropical trees, these are obviously the smells of their home, but they weren’t drawn to the smell of grass, and they really hated going into water that smelt like a swamp tree, and this is obviously what they might expect.
Chris Smith: So how does the carbon dioxide affect that?
Kat Arney: Well the researchers did the same tests on clown fish that were put into water that contained higher levels of carbon dioxide than normal, and because carbon dioxide forms an acid in water it has a lower pH, and so the team shifted the pH of seawater from 8.15 to 7.8 and, interestingly, this is the shift in pH that would be expected by the year 2100, if we keep pumping out CO2 in the atmosphere at the current rate.
Chris Smith: And when they did this what was the impact on the fish?
Kat Arney: Well it was very sad really. The scientists found that in the more acidic water the fish were still attracted to the smells of home, to anemones and tropical trees, but they also went for the smell of grass and the smell of the nasty swamp trees as well. But it gets worse, because if the researchers dropped the pH a little bit more, down to 7.6, the clown fish just stopped responding to any smells at all, even if they were put back in fresh seawater.
Chris Smith: Well sticking with the sea, it’s the thing that we think spawned all of us, we all came from the sea one way or another, and we also think that there was a finite time when life, complex animal life, sprung into existence. But scientists have now wound the date back of when that life springing into existence occurred with a paper in Nature this week.
Kat Arney: Cast your mind back around 540 million years and you’ll get to the end of the neoproterozoic era. Now this is the time of climate extremes and phenomenal bursts of evolution that culminated in the emergence of the very first animals. These are our ancient ancestors. But now, new results from a collaborative team of researchers from the US, Australia and the UK pushes back the origin of animals to further than 635 million years ago. This was before the end of a major ice age called the Maranoan Glaciation.
Chris Smith: But the thing about the 542 million years was that that was the time when the fossil record stopped. There are not hard animals around prior to then, so how are this team saying they’ve got evidence for animal life earlier than 542 million years?
Kat Arney: Well this is very clever because the researchers looked for the presence of specific chemicals in rocks and oils deposited in the fossil record, and these are known as C-30 sterols. These are steroid chemicals produced by very, very primitive ancient sponges called demosponges, and these were thought to be one of the very, very earliest forms of animal life.
Now they find very high levels of these C-30 sterols in an area called the South Oman Salt Basin, this is at the south eastern tip of Arabia, so it certainly suggests that these animals, in the form of these little wee sponges, were around much earlier than we previously thought. Now there’s already evidence of sponge fossils from around 540 million years ago, but this sets the clock back even further and marks the oldest known so far discovered animal life.
Chris Smith: So how far back do they think they can push that time?
Kat Arney: Well using their analysis, the researchers have pinpointed the development of animals to the Cryogenian period, this is roughly 850-635 million years ago. Now their analysis showed that the oldest sponges that could possibly be was around 750 million years old, so these new results certainly set the clock back on the evolution of animals and put it somewhere between those two dates.
Chris Smith: And do they give any indication as to why we’ve got this magic number 750 million years, was there anything going on at the same time that could have triggered them to pop into existence then?
Kat Arney: Well around this period of time there was intense glaciation across the earth, and this obviously affected the depths of the oceans and the chemistry of the oceans as well because you’re sort of freezing lots of ice into the sea changing its depth, and so this is thought to have triggered a big burst of evolution around that time and led to the development of little animals, these little sponges.
Chris Smith: So older even then than that crusty old sponge everyone has lurking under the sink. Thank you, Kat. That was Kat Arney from the Naked Scientist with a look at some of this week’s top science news stories. And if you’d like to follow up on any of those items the details are all on the Open University’s website, that’s at open2.net/breakingscience.
In just a moment, we’ll be hearing about a new way to find out what’s down to nature and what’s down to nurture when it comes to how a child grows up. But first to perhaps the most unlikely example of adoption that you’d expect to find in nature. A butterfly caterpillar that gets brought up by ants. Jeremy Thomas.
Jeremy Thomas: We’ve been looking at some very rare butterflies that live as caterpillars and chrysalises inside ants’ nests. They live there for up to two years, they’re very rare creatures and we’ve been looking at how they actually succeed in living in ants’ nests and exploiting all the resources inside an ants’ nest without being killed by the ants themselves.
Chris Smith: Because ants would normally eat things like these kind of caterpillars, because that’s what they do.
Jeremy Thomas: Absolutely. And certainly anything that tried to get into the ants’ own nest they’d kill straight away.
Chris Smith: So how are these guys doing this?
Jeremy Thomas: Well we already knew that they produced chemicals that mimic the chemicals that the ants themselves make. Every species of ant has its own smell, and even each colony of ants has a subtly different smell, so we already knew that the caterpillars could produce very similar cocktails of chemicals, and when the ants smelled these they not only recognised them as their own but carried them into their nests. What we didn’t know was once they were in the nests why they were treated with such special care. In fact, the ants inside the nests will feed these caterpillars with food, in preference to feeding their own ant grubs, to the extent that when times are really hard, if the colony’s starving they’ll kill their own ant grubs and feed them to these intruders.
Chris Smith: So the big question is what on earth is the caterpillar doing in addition to smelling like them in order to make them behave like this?
Jeremy Thomas: Exactly so. And we’ve known for some years that the caterpillars could make sounds, but we thought that sound was a very crude method of communication in ants, but we did know the adult ants do make little scratchy noises. The ants have two segments of their abdomen, that’s the last section of their bodies, that they rub together and one of these sections has a whole series of grooves on them and the other half has something that we call the plectrum, that is a bit like the plectrum of a guitar except it itself has several grooves, and when they rub these two surfaces together it produces sort of chirruping type noises. And the chirruping noises can vary from ant to ant, and from species to species because of the distance and the width and the thickness and the space between the grooves, but also in the speed and rhythm at which the ants rub the bits of their body against each other.
Chris Smith: And so your hypothesis is then that these caterpillars are somehow making the same sounds and that’s what’s fooling the ants into treating them like their queen?
Jeremy Thomas: Yes. There are really two breakthroughs in this. I’d noticed for many years that once they were in the ants’ nest they seemed to be treated as if they were queen ants. Now we knew this couldn’t be through chemical secretions and so an obvious candidate was that they were making sounds. But no-one at that time knew that queen ants made different sounds from worker ants, so the first thing was to see if that was the case, which it proved to be, and then if these caterpillars and chrysalises were actually mimicking the queens, and that proved to be the case as well. So there was really two steps to this story.
Chris Smith: How did you do it? Were you threading very intricate little microphones into ant nests and listening to what they were doing?
Jeremy Thomas: Yes. We had captive nests in the laboratory, quite small simple ones in soundproof rooms, so we were able, for the first time, to place microphones inside captive ant colonies and record the normal sounds that ants make when they’re doing their normal business.
Chris Smith: And then if you play those sounds back to them do they respond as though they’re responding to another ant?
Jeremy Thomas: Exactly that. When we played them through tiny miniature speakers to the same colonies or different colonies of laboratory ants we found that they clustered round those speakers and tapped them, and in the case of queens’ sounds they did a very strange sort of behaviour that we call on guard attendance. They sort of sit on the speaker or microphone and they sit hunched up on it with their jaws slightly apart, on guard like soldiers, and the queen sounds particularly induce this behaviour.
Chris Smith: And the caterpillars make the same sounds do they?
Jeremy Thomas: Yes. The chrysalis in fact makes a sound that’s closest to the queen of all, but the caterpillar sounds are also closer to the queen’s than the sounds the ordinary worker ants make. And again, when we played back the sounds of the chrysalis to the ants, we found that the ants were reacting to the miniature speakers in exactly the same way as when we played queen ant sounds. In fact, if anything, they were behaving in more extreme forms and it attracted more ants and they sat on it and behaved almost as if they were super-queens.
Chris Smith: Jeremy Thomas describing how the rare blue butterfly species, Maculinea rebeli, mimics the sounds and smells made by ants to try to convince them to bring it up as one of their own. He’s based at Oxford University and he’s published that work in this week’s edition of the journal Science.
Now, as a special treat Jeremy has also sent over some of the sounds that he recorded during that study, so this is what the queen ant sounds like [sounds]. Certainly an improvement on James Blunt, and here’s the caterpillars copying them [sounds]. So not really too bad at all for one species trying to sound like a totally different one.
Now from colonies of ants to colonies of people, and researchers have found a clever way in which to disentangle the effects of a mother’s behaviour on her developing baby from the effects of her genetics. In other words, scientists have found a way to separate nature from nurture. They can do this by comparing children who were conceived by egg donation via IVF against those conceived also by IVF but using their own mother’s eggs. Here’s Anita Thapar.
Anita Thapar: The reason we were interested in using a completely novel type of approach is to answer a specific question that many researchers have been interested in for some time. And that’s relating to the effects of what happens to people in the womb, pre-natal risk factors and the effect on health later on. And one of the areas of interest has been exposure to cigarette smoke in the womb and whether that has an effect on health.
It’s known that being exposed to cigarette smoke has an adverse impact on the baby, for example it’s known to lower birth weight. But more recently there’s been a lot of interest in whether it has an impact on children’s behaviour as well.
Chris Smith: So why do you need to study IVF children in order to answer that question?
Anita Thapar: Okay, the interesting thing about looking at the IVF children is because although the majority of children born by IVF are genetically related to the mother who undergoes the pregnancy, there are a group of children who are born by more unusual methods, for example egg donation or by embryo donation, where they may be genetically unrelated to the woman who undergoes the pregnancy.
Chris Smith: So what this means is that you’ve got quite an elegant situation here where you have a baby which is ungenetically related to the mother, so you can look at the situation the mother’s putting the baby in and see if the same factors that would affect, say, a baby born to a mother who smokes who is related to that mother also affect a baby that’s genetically unrelated to that mother.
Anita Thapar: That’s right, and that’s really important because if cigarette smoke has a really true effect on the baby’s health then it won’t matter whether the mother and baby are related, and that’s actually what we found for the effects of smoking on birth weight, didn’t matter whether the mother was related or unrelated, the link remained strong.
However, for antisocial behaviour – by this I’m not talking about very severe behavioural problems but more within the normal range, behaviours such as temper tantrums or fighting – but from antisocial behaviour we found that that wasn’t the case, it was quite different from birth weight. There was a strong link in those genetically related mothers and children but not in the unrelated group, and that suggests that the previously observed links may just be artefactual and just explained by something to do with the mother’s inherited characteristics that she’s passing onto the child, and not a toxic effect of cigarette smoke on behaviour.
Chris Smith: Now I know that you’ve controlled your study by comparing two groups of IVF babies, those related to the mother and those that are genetically not related to the mother, but is there not the possibility that because they’re having IVF they’re already a bit exceptional and that that difference, because there’s clearly already a problem, that could exaggerate any differences that you’re measuring, perhaps sensitivity to cigarette smoke, and therefore the real situation in the normal pregnancy wouldn’t maybe be quite so acute?
Anita Thapar: Well it’s really interesting because, you know, this is a very special and selected group, well how might that affect findings? Well the thing here, we’re not looking at absolute levels of smoking or absolute levels of behaviour. What we’re looking at is the strength of the links between the two. Actually for the genetically related mothers and babies, the strength of the links for both birth weight and behaviour is pretty similar to those found in other studies. And of course the other observational studies, the mothers and children will always be genetically related. So it suggests that the findings might be generalisable.
Chris Smith: It is a very elegant approach that you’ve taken and you’ve used it to just look at one aspect here, which is the effect of smoking on two outcomes. Could you use the same trick, the same technique, to look at other things and, if so, what do you think would be worth looking at?
Anita Thapar: Yes, definitely. We set out to examine a number of different risk factors and a number of different outcomes, so we will be looking at this in the future. We are mainly focusing on risk factors and outcomes that have been previously demonstrated in other types of research, and so where there’s been a question, oh is this really causal or is it, you know, due to some sort of unmeasured inherited factor. The other thing we can look at is prematurity, and again there’s a number of health outcomes that we might be able to look at.
Chris Smith: Anita Thapar from the University of Cardiff discussing a new way to separate environmental factors from genetics. She’s published that work in this week’s edition of the journal PNAS.
You’re listening to Breaking Science with me, Chris Smith, and it’s time now for this week’s ‘Stuff and Non-Science’, where we massacre myths. And trying to measure up to standards this week is Diana O’Carroll.
Diana O’Carroll: This week on ‘Stuff and Non-Science’, Jeremy from Australia wanted to know is it a myth that you can predict a child’s adult height by doubling it when they are two years old. With the answer, Tim Cole.
Tim Cole: It’s something that’s been said a great deal, I’ve certainly heard it said, but I don’t know where it comes from. For boys it works moderately well, for girls it doesn’t because, of course, girls as adults are shorter than boys and yet at age two boys and girls are really rather than similar in height. I’ve heard it suggested that you should double girls’ height at 18 months to get over that, so you end up with a shorter prediction.
Both these predictions are pretty rubbish in my view, and you can do much better than that, although it’s a well-kept secret. And it just happens that at the moment I’m involved with redesigning the charts which new parents get when their baby’s born.
They get a set of growth charts in their red book, the PCHR, and these are being redesigned to include the World Health Organisation growth charts, and along the way we’ve decided to include with those, what we’re calling an adult height predictor, and you can use this to predict the height of your child at any age. And this is a prediction which we think works well, and it will be within 6cm of the true height for about 80 per cent, and so you’ve got a good chance of being within 6cm and a quite reasonable chance of being quite a lot closer than that.
Diana O’Carroll: So you can predict how tall the kid might be, but it’s not so simple as doubling a two-year-old’s height. Tim Cole of the Institute of Child Health at UCL where he’s involved in drawing up the growth charts used by the World Health Organisation.
Keep your myth suggestions coming in to email@example.com.
Chris Smith: And I think the moral of that story is don’t put your child on a traction machine if you don’t like the prediction that comes out at the end of the day. Thank you, Diana. That was Diana O’Carroll with this week’s ‘Stuff and Non-Science’.
That’s it for this time. We’ll be back next week with another round-up of global science news.
Breaking Science is produced in association with the Open University. You can follow up on any of the items included in the programme via the OU’s website, that’s at open2.net/breakingscience, or alternatively you can follow the links to get there from the BBC Radio 5 Live Up All Night website.
The production this week was by Diana O’Carroll from thenakedscientist.com, and I’m Chris Smith. Until next time, goodbye.
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In the news
'Thymic stromal lymphopoietin overproduced by keratinocytes in mouse skin aggravates experimental asthma'
by Zhang et al (2009)
in PNAS vol 106, pp 1536-1541
'A whole-genome scan and fine-mapping linkage study of auditory-visual synaesthesia reveals evidence of linkage to chromosomes 2q24, 5q33, 6p12, and 12p12'
by Asher et al (2009)
in American Journal of Human Genetics, Vol 84
'Ocean acidification impairs olfactory discrimination and homing ability of a marine fish'
by Munday et al
in PNAS Early Edition, January 2009. DOI: 10.1073_pnas.0809996106
'Fossil steroids record the appearance of Demospongiae during the Cryogenian period'
by Gordon D. Love et al (2009)
in Nature vol 457, pp 718-721
Jeremy Thomas for 'Queen Ants Make Distinctive Sounds That Are Mimicked by a Butterfly Social Parasite', by Francesca Barbero, Jeremy A Thomas, Simona Bonelli, Emilio Balletto, Karsten Schönrogge in Science
Anita Thapar for 'Disentangling prenatal and inherited influences in humans with an experimental design', by Frances Rice, Gordon T. Harold, Jacky Boivin, Dale Hay, Marianne van den Bree, and Anita Thapar in PNAS
Tim Cole for 'Stuff and Non-Science'