Briefing chat: How hovering bumblebees keep their cool

0:03Hello and welcome to the Briefing Chat Podcast, the Friday show where we give you a roundup of the latest science news courtesy of the Nature Briefing, which is Nature's daily email newsletter that tells you all about what's going on in the world of science. And joining me to discuss this week is Sharmney Bundel. Hey, yeah. Yeah, I've got some brain science that I'm bringing to the Briefing Chat podcast this week. And it's all about sex differences in our brains, which is, if you're not aware, kind of a controversial topic. And this is some new research on that. Yeah, because it's hard to figure out what causes these sex differences, right?

0:42Whether it's like the environment, whether it's society or something like internal to us, right? Yeah, huge questions about that. I went to the Wikipedia article on neuroscience of sex differences. And the first paragraph is just different papers that are sort of disagreeing with each other. And no one's quite sure what they mean. And I don't think this is going to magically solve anything, but it is interesting. I should say it's a preprint. It's on bioarchive, so it hasn't been peer reviewed and published in a journal. but this has been reported by Nature News. And basically what they've done in this study is fMRIs of 1 ,286 people from the age of eight to a hundred.

1:18And they are looking at sex differences. They have sex at birth of these people. They don't have their gender. And it's just a little snapshot of their brain at their current age and information about different types of connections within the brains. So there's structural connections, which is just literally like where the physical neurons are linked to each other. And there's also functional connections. So that's more about what the neurons are doing. And it's about synchronised brain activity in the neurons between different regions when they're sort of synced up. So they looked at those two things and they did in fact find brain differences, which is not super surprising.

1:58But what they have found is in childhood, those brain differences were kind of minimal. At puberty, they massively increased. And some of those differences continue to grow through life when you compare the people of different ages. And as you said, this is a snapshot, right? So they're not following the same people throughout time. This is like snapshots of different people at different ages. Yeah, exactly. So there's a lot of confounding factors, which we'll get on to. But to give you an idea of some of the more sort of specific findings they're kind of like interesting little things going on here so for example with the older men the older they were the more there were strong functional connections between the two hemispheres of the cerebellum and that's part of the brain that's used in motor control and also structural connections also grew stronger in the men than in the females when you looked at the older people whereas with the female participants they found stronger functional connections between regions referred to as the default mode network.

2:58And this apparently deals with higher order processes. So it's all very sort of detailed specific things, but it's actually really relevant to things like mental health. So for example, this default mode network, hyperconnectivity in that kind of area has been linked with depression. And women tend to show higher frequencies of depression. Women are more likely to get anxiety, whereas men are more likely to have issues with substance abuse, alcohol addiction. Boys are more likely to be diagnosed with autism spectrum disorder. So there's a lot of potential here that understanding exactly how our brains are different could lead to maybe better treatments because you kind of know what you're looking at a bit more rather than perhaps treating everyone the same.

3:48And I suppose this was just these snapshots, so they won't have looked into exactly how this happens or why this happens. Yes, then I think the why is the controversial bit, as you were saying earlier. And there's certainly people quoted in this Nature article who are very much not convinced that the differences that they found are sex based differences, that they're down to this sex at birth and not gender social roles, how you're growing up. So, for example, it's quite likely that hormones play a big influence and there seems to be some sort of mapping with the changes in the brain and sort of hormonal changes that we know of.

4:27But there's also, yeah, changes in how we're raised and changes in our experience as men and women in the world. So, for example, one scientist who was interviewed for this said that this higher prevalence of depression and anxiety in women is linked to socioeconomic outcomes, sexual violence, body shaming. All of these things are likely to contribute to brain changes. And she says sex is just one part of why we have health disparities. And another researcher says this could reflect differences in education, parental treatment, physical activity or social sex. Yeah, because I mean, I guess the brain is a very plastic organ and it can be very responsive.

5:08And while, as you said, these differences become more pronounced during puberty, this is a time of a lot of physical changes, but also a time where we, you know, maybe enter our roles in society as men or women a bit more. Yeah. And I think one of the controversial questions is if you're talking about differences in male and female brains, there is this sort of social expectation that human brains fall into two distinct categories. You know, they're either one type or another. And there's been previous research that's been really looking into this. One of the researchers who's actually quoted in this article as well has done previous research where they've concluded that the brain is more of a sort of mosaic of different features.

5:54so you might have some features are more common in men some features are more common in women but that there's no sort of really distinct clear differences they talk about sexual dimorphism a lot you know like in animals you have like mallard ducks you'd have like all the males have green heads and are very pretty and all the females are brown like that's a sexually dimorphic species are our brains sexually dimorphic a lot of researchers fall on the side of no because there's so much overlap between all the different features. And I think that's a very important sort of social question, because it seems to lead into ways that we might treat and categorise men and women.

6:34But of course, the real biological differences are also really important in how we treat men and women when it comes to brain disorders, mental health conditions, things like that. So the author of this study says that she aims to try and disentangle some of the effects, the different factors that we've talked about, and also follow individuals' brain data over time, which would also be really interesting. And then she hopes that this would reveal insights that can help maybe personalise some mental health treatment. Well, fascinating stuff. It's always interesting to hear more about our own brains.

7:08I guess we're a very self-centred species like that to sort of hear more about how we are. But I'm going to talk this week about a species that has its own sort of sexual dimorphism. I'm going to talk about bumblebees. And as you know, most of the bumblebees that you see are probably female. There are only a few males that carry the sperm. But that's not really what this story is about. This was a story I was reading in Science about how bumblebees don't overheat when they're flying. I feel like I have to bring up at this point the sort of famous myth that bumblebees can't fly. Physicists don't know how bumblebees manage to fly.

7:45That's not true, is it? That is not true. And I actually once tried to trace the origin of that quote. And it seems like no one's entirely sure where that quote came from. So that's not the case. We have some idea. But there are a lot of mysteries about bumblebee flight. Like it's still quite a complicated thing. They are sort of weirdly clumsy looking animals, to be honest. But the one thing we do know about them flying is it generates a great deal of heat. In fact, bumblebees, it's known, and I've actually done experiments like this myself, they're able to thermoregulate. So they're able to use their wing muscles to heat themselves up.

8:23So if they get chilly, they could just vibrate their wings and warm up, just like we would go for a little jog. They can just flap their wings. Yeah, it's the same sort of thing as shivering that we do. So bumblebees are known to do that. And it's known in many insects that flying generates heat. In fact, dragonflies as well will take a dip in some water to cool themselves down to prevent themselves from overheating. And many insects will land when it's too hot as well, presumably because they're overheated somewhat. So these researchers have been looking into how the bumblebees may stay cool as they're flying.

8:57So there are some things that have already been known about it. So it was already known that the bees transported haemolymph, which is kind of like their version of blood, from their warm chest to their cooler abdomen. But it wasn't known what the effect of the actual air moving because of the wings was. So that's what they were looking into here. OK, so this is basically about how bees cool down. It's all very well using your wings to heat yourself up. But if you're in a really hot place, you don't want to be stuck unable to fly because you're going to overheat. Yeah, that's not a great way to survive the world.

9:32And this could be relevant to climate change as well, because as the world heats up, we want to know how bees are going to be able to adapt, if they'll be able to adapt, and potentially what we can do to help them survive. So yeah, there was not much known about how the actual air movement cooled down bees. So what these researchers did is they put them in a tiny little chamber. I will link to the story here and there's a little video where you can watch them flapping about in this chamber. And they used some dry ice and dry ice is just solid carbon dioxide. And as it evaporates, it generates like a little fog.

10:07And so they put the dry ice in there with the bee that was hovering in this tiny cage. And as it flew, they could see the disturbance in the air in this fog. And they could use that to understand like how the air was moving around the bee. Oh, amazing. So this was a cage so that the carbon dioxide could get out. They weren't just suffocating the bees. They were not suffocating the bees. That is a valid clarification. They're not trapping the bees with dry ice in a tiny chamber. No, the cage is to keep them hovering in place so they can see the vortices and the fluid dynamic of how the air is moving.

10:46Yeah, exactly. Kind of similar to the video you did a few years ago about birds flying through bubbles where they could see the sort of vortices generated underneath their wings. I'll link to that as well in the show notes. It's a fun watch. But anyway, for the bees, they found that they get the air moving around them at between 0.25 to 2 metres per second. So quite fast, especially because, you know, bees are quite small. It's a breeze, yeah. And they found that it could actually cool them by 5 degrees centigrade. So that is an amount of cooling that was described as whopping by a researcher who was interviewed in this article.

11:21That is quite a lot. And is the idea here that if you're flapping your wings, air is flowing and this is just a sort of side effect that like, oh, yeah, I guess the air is kind of cooling you down as well. Or is there some indication that this is an adaptation specifically for cooling them down? It's unclear whether it's a thing that happens that the bees just use or it's a thing they're actually trying to do. We don't know that yet, but by understanding this, they can help understand how it is that bees will be able to adapt to this warming world, as I say. And this is something that we just didn't know about before.

11:54What is less clear is whether this just happens when they're hovering versus when they're flying. So in these cages with the dry ice, they were just hovering in place. And that generates a downdraft, which one of the researchers interviewed in this article thinks may be particularly important for cooling. Whereas when you're going forward, you'd get less of that downdraft. So it's unclear if you'd get the same amount of cooling. And presumably, yeah, this is going to be particularly interesting if it is relevant to a lot of other insects, other bee species. Because as you say, we've got climate change could be warming different parts of the world.

12:30Different bee species are relied on for pollinating different kinds of crops and wild plants. Something that's worth understanding. Yeah, definitely something worth understanding. And if we want to conserve and protect pollinators and other insects, any insect, then these are good things to understand, to understand how they may adapt and whether they might move or whether they may change what they do in response to climate change. So it's all part of that sort of broader picture. But it's also really fun. Again, I will link to the article, which has a nice video that you can watch. And it's just very impressive to see this bee flapping away and the air currents moving around it in this study.

13:09And I've just seen that that research was quite suitably published in the Proceedings of the Royal Society B. Yes, very good. It was indeed published there. But I think on that dreadful pun, that is all we've got time for this week. So if you at home would like to read more about those stories, we'll link to them in the show notes. And we'll also link to where you can sign up for the Nature Briefing so you can get even more stories like them directly to your inbox every day. And if you feel the need to email us with any bee puns, you can. We're podcast at nature.com. Send them all Nick's way. He will enjoy them.

13:48And we're also on various social media. We will refrain from posting bee puns there, but we are at nature podcast if you want to follow us. I'm Sharmini Bandel. And I'm Nick Petra-Ciao. Thanks for listening.