Host: Benjamin Thompson
Welcome back to the Nature Podcast. This week: the mysterious secretions of ant pupae.
Host: Noah Baker
And the latest from the Nature Briefing. I’m Noah Baker.
Host: Benjamin Thompson
And I’m Benjamin Thompson.
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Host: Benjamin Thompson
First up on the show, how seemingly inactive ant pupae actually contribute to the colony in a previously unknown way. Now, ants are very social creatures. Each one plays a key role in the collective, working together for the benefit of all. And for some species, this ‘working together’ is a lifelong endeavour, with ants at different developmental stages contributing different things. Ants start life as eggs, which can help spread important pheromones around, and in their next life stage as larvae, they can produce silk for nest building. But not all of the life stages are thought to contribute. Before the larvae become adult ants, they go through an intermediate stage where they become pupae – essentially immobile sacks that metamorphose into adults. However, despite pupae’s passive nature, adult ants still seem to spend a lot of time around them. So, what’s going on? Why spend so much time with a seemingly inert life stage? Well, a new paper in Nature may have shed some light on that, revealing that even these stationary pupae actually play a role in the wider ant colony. Reporter Nick Petrić Howe caught up with one of the authors, Orli Snir, from the Rockefeller University in New York to find out more and started by asking her, why look at the pupae, when it seems they don’t do an awful lot?
Interviewee: Orli Snir
There is no record in the literature of any contribution of the pupae to the ant colony. So, the question is, why are they getting taken care of by the adult ants? Solitary insects, for example, the pupae are perfectly fine when they are at this stage with no parental care. So, what has changed within the ant pupae that suddenly they need to be taken care of?
Interviewer: Nick Petrić Howe
Right? So, in contrast to other insects, the adult ants are actively taking care of the pupae.
Interviewee: Orli Snir
Yes. From the looks of things, you can see that adult ants spend a lot of time in close contact with pupae. But we don't know of any contribution of pupae to the ant colony. So, the question was, why exactly do they spend some time with them?
Interviewer: Nick Petrić Howe
So, in this paper, you looked at the pupae, and the first thing you did is you isolated the pupae from the adult ants. What did you find when you did this?
Interviewee: Orli Snir
First of all, it took a lot of adjusting because I needed to figure out what are the right conditions that they need in order to survive. In that case, I was actually the adult ant. I was the caregiver. And at this point, I started to see that they isolated pupae secrete daily droplets of fluid.
Interviewer: Nick Petrić Howe
And so, when you saw this, were you surprised at what was going on here, that there was this fluid?
Interviewee: Orli Snir
I was extremely surprised. I mean, the initial discovery of the pupae secreting fluid was very much unexpected.
Interviewer: Nick Petrić Howe
If you left this fluid there and didn't remove it, what happened to the pupae?
Interviewee: Orli Snir
Indeed, at the beginning, I just left the fluid, and since it is pretty large volumes compared to the pupae size, then the pupae will just drown in their own fluid. They will just die.
Interviewer: Nick Petrić Howe
So, it seemed critical the fluid needed to be removed. So, then what happened once adults were reintroduced?
Interviewee: Orli Snir
The adults seemed very attracted to the fluid. They immediately approached the pupae and they consumed specifically these said droplets of fluid, even going from one pupae to another.
Interviewer: Nick Petrić Howe
And as I understand it as well, the larvae, this juvenile stage of ants, quite liked the fluid too. So, how did the larvae factor into all this?
Interviewee: Orli Snir
So, the larvae in ant species are immobile. So, they are dependent on adult ants. So, we discovered the adults prefer to take young larvae and put them on top of the pupae, where they can consume this fluid. And so, we found that this fluid is important for them to grow and to survive.
Interviewer: Nick Petrić Howe
And you also had a look at what the fluid is sort of made up of. What did you find here?
Interviewee: Orli Snir
So, when we looked at the molecular composition of the fluid, we found a lot of metabolites and proteins.
Interviewer: Nick Petrić Howe
And in the paper, you describe this protein- and metabolite-rich liquid as an important source of early larval nutrition. So, in this paper, most of the experiments we talked about, they started off on the clonal raider ant, but you showed this finding seems to happen in some other species of ants as well.
Interviewee: Orli Snir
Yes, that was actually a very pleasant experience because I went out to Central Park in New York, and collected a bunch of other ant species. And what I saw is that all of these are secreting fluid during pupation. So, this means that this is a crucial mechanism that probably coincides with ant eusociality.
Interviewer: Nick Petrić Howe
So, this coincided with ants becoming very social organisms, eusocial, in fact. So, do you think then that this is widespread amongst ants and this isn't an example of each of the ant species you tested coming across the same sort of mechanism?
Interviewee: Orli Snir
Yes, since we've sampled it from very different subfamilies, some are more ancient, some of them are young, in the process of evolution. So, we are confident that this actually happens in all other ants.
Interviewer: Nick Petrić Howe
And so, what do you think are the implications of this finding?
Interviewee: Orli Snir
I think one of the major implications is to shift our perspective of how we see the colony from an adult centric perception into a network perception because this is only a very small example of the intricate networks that exist in ant societies.
Host: Noah Baker
That was Orli Snir. For more on this story, check out the show notes for a link to the paper and a News and Views article.
Host: Benjamin Thompson
Coming up, we'll be hearing about the latest SI prefixes for giant and tiny numbers. Stick around for that. Right now, though, it's time for the Research Highlights, read by Dan Fox.
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Dan Fox
When you imagine caveman cuisine, your mental image probably stops on a hunk of meat roasting on a spit. But researchers are expanding our understanding of the Palaeolithic menu. A team used a scanning electron microscope to identify plant cells found in caves previously inhabited by Stone Age humans. They report that 13,000 years ago, in what is now Greece, the people living there had a varied and flavourful diet that included bitter vetch and grasses processed into something like bread or porridge. Meanwhile, in Shanidar Cave in Iraqi Kurdistan, the authors found remains of wild peas, mustards and pistachios that were cooked and eaten at least 40,000 years ago. At both sites, damage to the plant cells is consistent with soaking, grinding, mashing and heating – techniques still used today to turn bitter, astringent and even potentially toxic plants into culinary delights. Sink your teeth into that research in Antiquity.
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Dan Fox
More than 30% of shark and ray species are edging towards extinction, mainly because they're caught unintentionally by commercial fishing operations. But a new device might help keep some of these threatened species away from fishing hooks. The device emits short electrical pulses to overstimulate a shark’s electrical sensors. When attached to a baited hook, it creates an electric field that drives sharks away. A team of researchers trialled the apparatus – called SharkGuard – in a tuna fishery in southern France. They found that when hooks were fitted with the device, it reduced accidental catches of blue sharks by 91% and led to a 71% decrease in the by-catch of pelagic stingrays. The team say that large-scale deployment of similar devices could help to slash the number of sharks interacting with fishing equipment. If you're hooked on that research, read it in full in Current Biology.
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Host: Noah Baker
Finally on the show this week, it’s time for the Briefing chat, where we discuss a couple of stories covered in the Nature Briefing. This week, I’m going to go first, and I have a story about blood meals, mosquitoes and disease, that I read in Nature.
Host: Benjamin Thompson
Right, okay, so mosquitoes, famously, one of the most important all-time vectors for disease, carrying all sorts of viruses and malaria, of course, and so on.
Host: Noah Baker
Yeah, absolutely. So, this isn't really so much a story about mosquito-borne disease, although that's very relevant. This is really a kind of an alternative way to surveil disease, I suppose, or to better understand infectious disease by using mosquitoes. So, this is a technique that was presented recently at a conference in Malaysia, and the basic concept is can scientists try to sample the blood meals that mosquitoes are taking, so when they suck the blood from their hosts, and look for antibodies to get an understanding of how prevalent a disease might be, any disease, in fact, in a population.
Host: Benjamin Thompson
Right, so an indirect way then of sampling what's going on in the world. So, if a mosquito bites me, let's say, and then flies off somewhere, you then sample it and can get a sense of maybe what infection I have. Is that about right?
Host: Noah Baker
Yeah, precisely. So, essentially, when we have most infections, or any infection that triggers an antibody response, those antibodies, that we've heard a lot about recently owing to the pandemic, will hang out in your blood for a significant amount of time. And so, if there are antibodies for coronavirus, for example, in the blood, then you can get a sense that the person the mosquito has fed on has been exposed to coronavirus in the previous several months. And you can expand that further by also adding in DNA. So, you can get a sense of which animals have been fed on and what diseases they might have been exposed to.
Host: Benjamin Thompson
So, not just mosquito-specific diseases, then? Any disease that I have an antibody to? Well, that's quite something.
Host: Noah Baker
Yeah, essentially, what these researchers are trying to do here is use the mosquitoes as little sample gatherers. When they take a blood meal, they suck up a bit of blood, and then if you can extract that teeny, weeny little bit of blood out of the mosquito, then you have a tiny sample of blood from your population that's been gathered randomly by a mosquito. I mean, whether or not exactly it's random is something that I'm sure that scientists can discuss. The ecologist in me is immediately raising red flags there when I say the word ‘random’. But you essentially have a tiny sample from your population that you can assess for diseases. And so, this has been done in Brisbane in Australia – 55,000 mosquitoes were gathered over about a year period. And specifically, the researchers were looking at a virus called Ross River virus, which is a debilitating mosquito-borne disease endemic to Australia, related to dengue and Japanese encephalitis, yellow fever. And they did find mosquitoes that had blood meals in them. So, specifically, they found 480 mosquitoes had some tiny samples of blood. And then they found out that more than half of those were from people, and about 9% from cows, 6% from kangaroos. So, there was a mixture of different animals that had been fed on by these mosquitoes. And then they went further to analyse the antibodies in these samples.
Host: Benjamin Thompson
And what did this antibody sampling reveal then?
Host: Noah Baker
Yeah, well, they found that more than half of the human samples had antibodies against the Ross River virus, which is a really high population, according to the researchers involved, and close to three-quarters of the cows and kangaroos also had evidence of past exposure. And this isn't the first time that a study like this has been done. So, there is a way of gathering this kind of like broad-level information. And the results were interesting to them. They were finding a way to sample these populations on a broad scale using this indirect method with mosquitoes.
Host: Benjamin Thompson
I mean, you said, Noah, this was presented at a conference, right, suggesting it's not necessarily ready for primetime yet. What are some of the hurdles to overcome before this can be used to get a kind of an overall view of what might be going on in a particular area?
Host: Noah Baker
For sure, this is definitely an imperfect technique. So, there are a whole bunch of things that could potentially hold this up. One, is that while you can get a sense of a population in an area because mosquitoes don't tend to fly very far, and so you can reasonably assume a rough radius for where your mosquitoes have been, you can't get much more granular information than that. So, you can't say exactly who was infected or the demographics of the people particularly, or the animals, or at what stage, or how or where. Those things are much more difficult to do. Also, it's difficult to do for really broad-scale surveillance because mosquitoes that have had a blood meal tend not to be very active. They're notoriously actually quite hard to capture. So, they captured 55,000 mosquitoes and only 480 of those had actually eaten blood. In general, when female mosquitoes have a blood meal, they typically try to find some a dark and moist to just hide and digest it, so they're not flying about. It's harder to catch them. And researchers are trying to get around that problem by creating special traps based on carbon dioxide, which mosquitoes are attracted to because it's breathed out by animals, to try to help gather more of those mosquitoes. And so, those are certainly limitations, but one of the big advantages is that this is completely non-invasive, right? You can gather these samples without having to capture the animals involved, or having to take loads of blood from lots and lots of different people. And so, it's a way to sort of broadly measure the transmission of a disease and learn about potentially even things that are very hard to study, like Japanese encephalitis, for example, which there’s very, very little data on. And this is definitely a tool in the epidemiologist’s tool belt.
Host: Benjamin Thompson
Well, that does seem like a cool, neat technique, Noah, and I'm sure we'll hear much more about it in future. But for the time being, let's move on to the story that I've got for you today, and it's something I also read about in Nature, and it's about finding new names for extremely big and extremely small numbers. And specifically, the prefixes used in the SI units used in the metric system.
Host: Noah Baker
I love it when I hear SI units because it makes metrology come to my head, which is one of my favourite nerdy subgenres of science. Tell me, what is it that metrologists are arguing about in incredible detail now?
Host: Benjamin Thompson
Well, get ready for this one. There is a lot of cool stuff in here. But let's give it a bit of background, if I may, Noah. So, again, a lot of people listening to this show will understand, will know these prefixes, right, things like nano, micro, milli, centi, deci, deca. On it goes, right. And so, that could be for a bunch of things. It could be for length, it could be for mass, it could be for data. And data is the key here, right. Because at the top of the scale, we've got exa, zetta, and yotta, right, which are enormous numbers with huge numbers of zeros after them, right. But, I mean, when I was a kid, I don't know about you, Noah, but I remember getting my first hard disk for my computer and it was like a couple of hundred megabytes. And like, this is just an expanse of space. But fast forward a few decades, and it's estimated that by 2030, the world is due to produce around a yottabyte of data per year, and that's 1024 bytes. And for context, if you were to fill up a DVD with data and keep going and then stack it up, a yottabyte’s worth of data would reach to Mars, okay. And it leaves the question, what's next? What happens after yotta, right?
Host: Noah Baker
Absolutely, and you can understand why scientists haven't come up with an official term for anything bigger than that up until now because I suppose it was unreasonable to think that there was going to be need for massive numbers in the general lexicon until things like data have come around. So, what's next? What's after a yottabyte? A yottabyte is 1024 bytes. What comes next now, according to the metrologists?
Host: Benjamin Thompson
Well, unofficially, some people were trying to fill that void, and they filled it with ‘hella’ and ‘bronto’ for 1027, right, and you actually could see those sort of in the wild. Google's unit converter said that 1,000 yottabytes was 1 hellabyte. And apparently, brontobyte appeared on at least one UK government website. But they are unofficial ones, right. And h and b, which are the sort of shortenings for that, are already use for other SI units, right, so they've had to go out. So, scientists needed to develop some new ones. And a couple of weeks ago, representatives from governments around the world met at the General Conference on Weights and Measures outside of Paris, and they voted on the new prefixes. Okay, and so, after yotta, welcome with immediate effect the ronna which is 1027, and the quetta, which is 1030. And for context, Earth weighs, around one ronnagram. So, there we go. So, we're at the extreme large end of the scale at this point.
Host: Noah Baker
It's interesting as well, that you have already found a use for the ronnagram right away, to measure the weight of the Earth. I mean, who knows how useful that actually is for most people. It's interesting because you wouldn't think that this is that important. But of course, it is important because these kinds of prefixes, especially the symbols that are used to describe them, there are a limited number of symbols that exist. And a lot of these symbols have already been used by other things. And you'd want to make sure that people aren't going to confuse them as they go forward, which is why metrologists have these meetings to discuss and vote and decide on what the new prefixes are going to be to describe these unfathomable numbers. And these are the latest prefixes that have arrived. But there haven't been any others that have been added for quite some time. So, they're a bit overdue this change, right?
Host: Benjamin Thompson
Yeah, I think 1991 was the last time that prefixes were added. And you're right, this wasn't that easy, right. So, a metrologist in the UK, Richard Brown, his name is, has been working on plans for this for like five years. And he presented this proposal at the meeting. And he and everyone else involved had to look for letters not used in any other symbols or prefixes. And the words had to kind of sound a bit like Latin or Greek. And so that's why we've got ronna and quetta (R and Q). And so, they sound a bit like the Greek words for nine and ten. But it's a tough gig because one of the ones that was originally thought of apparently sounded quite close to a Portuguese swear word, so that one had to be binned off pretty sharpish. But that's maybe one end of the telescope, if I may, right. That's the extremely large. Also, at this meeting, extremely small prefixes were decided as well. And so, enter the ronto, which is 10-27, and the quecto, which is 10-30. So, the other end of the scale, right. The scale kind of balances out. We’ve got these tiny, tiny, tiny, tiny, tiny ones, and these ones you can't even imagine, huge, at the other end, as well.
Host: Noah Baker
And importantly, names that reflect the numbers on the other direction. So, they are slightly different. Ronna goes to ronto and quetta goes to quecto. Is that correct?
Host: Benjamin Thompson
Yeah, the large ones end in an ‘a’, and the small ones end in an ‘o’. So, that’s where we kind of are right now. And when these will get pressed into service, it's kind of unknown to be honest with you. It seems more likely that the larger ones are going to be used before the smaller ones, right? You can imagine a world where we have a quettabyte worth of data before we work out what to do at the other end, for example.
Host: Noah Baker
Okay, so we've gone all the way up to 1030, and down to 10-30. What's next? What are we going to see next from the metrologists? What's the next big news we're going to see coming out of the conferences?
Host: Benjamin Thompson
Well, it seems to be that the answer is a fairly big shrug at the moment, Noah, to be honest with you. It's one of those ones – we'll figure it out when we get there. But there's talk about, do we need to start sticking two words together because all the letters of the alphabet have been used up now. But I guess we'll have to wait and see. Well, let's leave it there for this week. Listeners, if you'd like more details about the stories we discussed and where to sign up for the Nature Briefing to get even more like them delivered directly to your inbox, check out the show notes for some links.
Host: Noah Baker
And that’s all for the show this week. As always, you can keep in touch with us on Twitter. We’re @NaturePodcast. Or you can send an email to podcast@nature.com. I’m Noah Baker.
Host: Benjamin Thompson
And I’m Benjamin Thompson. Thanks for listening.