Welcome to STEMology – Show Notes

Season 1, Episode 37

Honey, I shrunk the birds, GLITTER, Maybe-dead-toothed-frogs, and Special neurons

In today’s episode of STEMology…

David and Sophie talks about the shrinking sizes of birds, sustainably produced glitter, frogs species with teeth that may no longer be around, and human’s special neurons with low level of ion channels

Honey, I shrunk the birds

The birds are shrinking and it might be dad’s fault. And by Dads, we mean humanity

They can tailor it to any wavelength, which means they can produce any color imaginable on the visible spectrum. They can make any colored glitter ever.

Maybe-dead-toothed frogs

The fact that the teeth have come back and look very teeth-like suggest that maybe there’s a simple genetic switched on and off that gives the frogs their teeth back.

Special neurons

So as the neurons get bigger, the density of the ion channels, so the number of ion channels per unit area on the neuron, also tends to get bigger, unless you’re a human, the human has way less.

This is a “kind of, sort of, vaguely close” copy of the words that David & Sophie speak in this episode.

IT IS NOT 100% accurate.  We are very sorry if we have spelt something completely incorrectly.  If it means a lot to you to have it corrected, email us at stemology@ramaley.media

STEMology s1e37

[00:00:00] David: Welcome to episode 37 of STEMology.

[00:00:02] Sophie: A podcast sharing some of the interesting fun, and sometimes just patently bizarre news in science, technology, engineering, or maths,

[00:00:10] David: Your hosts are Dr. Sophie Calabretto and Dr. David Farmer

[00:00:13] Sophie: In today’s episode of stem ology, we’ll be chatting about Honey, I shrunk the birds

[00:00:18] glitter,

[00:00:20] David: maybe dead tooth frogs and special neurons.

Honey I Shrunk the Birds

[00:00:23] Sophie: Dave, have you seen this new movie called honey? I shrunk the bird starring Rick Maraniss and Tippi Hedren.

[00:00:30] David: well, I’ve I haven’t seen the new movie, but I’ve, read the new research story. That is almost literally based on that premise.

[00:00:36] Sophie: Yeah, the birds are shrinking and it might be dad’s fault.

[00:00:41] David: it might be dad’s fault. And by dads, We mean humanity

[00:00:44] Sophie: We mean humanity and our constant desire to destroy the planet for every thing in it,

[00:00:52] David: So it on it. in it with it,

[00:00:56] Sophie: with it, buy it

[00:00:57] David: for it

[00:00:58] Sophie: for it

[00:00:59] David: upon [00:01:00] it

[00:01:00] Sophie: upon it. Continue Dave. Sorry.

[00:01:02] David: So it turns out that birds in the Amazon are shrinking or more specifically, They have decreased in mass over the past 40 years. Many species have lost nearly 2% of their average body weight per decade. Researchers report November 12th in science advances.

[00:01:18] Sophie: Yeah. So not only have so 2% is not nothing. Right. And I guess it’s happening over a decade. I mean, we would call that probably healthy weight loss, you know, in the.

[00:01:26] David: Okay.

[00:01:27] Yeah.

[00:01:28] Sophie: but I mean, no, if you don’t want to. but some species have also grown longer wings. And so they’re saying that, this all possibly has to do with the fact that because we’ve really invoked an aggressive kind of climate change, we’re getting all of these sort of erratic weather conditions and variable, you know, varying weather and the birds are maybe evolving to deal with that

[00:01:49] in a better way. And it has to do with size Dave size and cooling.

[00:01:53] David: Yeah. So there’s two things happening here. One is that the birds are shrinking and the reason you might expect birds to [00:02:00] shrink, if it’s getting warmer, is that as they shrink, they get a higher surface area to volume ratio, which means they can lose heat to the environment more efficiently. And the other thing that’s happening is as you say, they get larger wings, which may let them fly or glide more efficiently.

[00:02:15] So basically they generate less heat when they’re doing their bird thing and flying. Therefore, the authors of this study suggest that what’s happening is that these are both adaptations to the weather.

[00:02:26] Sophie: Yeah. So apparently we’ve known for a while that we’ve got a lot of north American migratory birds, who’ve been getting smaller for awhile. The problem is because their migratory, there could be some other factors as opposed to just climate change, because, you know, It could be things like degraded habitats depending on where they are.

[00:02:43] And so they went, okay, let’s look at some non migratory birds. And this is a very long, I mean, they’ve used data for like a hectic period of time. It’s like a proper long study. So we’ve got data on non migratory birds that was collected between 1979 and [00:03:00] 2019, and very specifically in an intact region of the Amazon.

[00:03:03] So we’ve got it spans out about 43 kilometers. And so the idea is this is untapped, you know, so we haven’t messed anything else up for them, except just the planet. and yeah, what they did is they had. So the data set included measurements such as, you know, mass and wing length and various things taken in-between that period for 11,582 individual birds of 77 species.

[00:03:25] And then they also looked at the climate data, you know, in great detail

[00:03:29] David: it’s a lot of work by a lot of different people in order to do this, but it’s, one of those

[00:03:33] Sophie: there’s a huge international team where I was like, I could start listing the universities, but it seems like a waste of our time. but yeah, the crazy thing was all, all 77 species declined in mass over this period.

[00:03:47] So some of the species only lost kind of, up to sort of 0.1% of their mass others lost up to kind of 2%. And I say, you know, this is the average body weight. Cause we’ve got, you know, different types of birds and things. My favorite [00:04:00] one, the Amazonian Motmot Dave who apparently

[00:04:02] David: Motmot.

[00:04:03] Sophie: shrunk from 133 grams to about 127 grams over the study period is an average weight.

[00:04:09] Anything that’s a small bird. That’s like quiet. That’s a big loss in mass.

[00:04:13] David: Big loss for a tiny birds. And so one of the other things that you see, so as you say, all species declined the mass over the periods, and that included as you say, the Motmot, which scarfs then food up in trees, but also birds that get food in different ways. So apparently the riff is kept at thrush, snatches up insects, predominantly ants, presumably off the forest floor.

[00:04:34] This also declined in mass.

[00:04:36] So. One of the things they say is that another thing that could influence body size is the availability of food. But the fact that all of these species, which eat all these different things, all declined in mass suggests that it’s the actual temperature and not some secondary effect of the temperature on the environment.

[00:04:52] Sophie: Yeah, exactly. Cause it would be like weirdly coincidental for the the very diets of 77 different species of [00:05:00] birds to all kind of decline in the same way. Right. And so apparently they’ve looked at, as we said, they looked at the climate average temperatures and you were looking at an overall increase in average temperature of about one degree in the wet season.

[00:05:11] And 1.65 degrees in the dry season, but what they think is actually a bigger factor is just these kind of the temperature and the precipitation has become far more variable. So you get these kinds of short-term fluctuations, especially like in the hot and dry season, then they think, you know, so basically the dry season can be very stressful for birds.

[00:05:30] You know, it’s harder to find food and water and all these things. And what they’ve seen is that the main mass decrease happened, mostly in one to two years, especially After hot, dry spells. And so they think that it’s kind of this weird, it’s like heat stress of this like varying climate, which is probably more of an indicator than just the fact that everything’s getting steadily warmer.

[00:05:52] David: Yes. and they get into it. In the discussion of the paper they get into what I think is a really interesting discussion, which is about how it’s being driven, [00:06:00] because there’s two ways it could happen. Right? There’s the evolutionary way where, okay, it’s getting warmer. Therefore, if you’re a smaller bird, you’re more likely to survive in there for pass on some genetic trait for smallness onto your offspring.

[00:06:12] Or there’s epigenetics whereby like the birds are actually responding in some way to the heat and then That’s being passed into their offspring without them dying, basically. whether it’s, Wellsian and or Darwinian evolution that’s happening basically. And they discuss it really, really cogently and the thing and conclude that they can’t tell because they haven’t done any genetics.

[00:06:32] but it’s really, really, really interesting.

[00:06:34] Sophie: Yeah. And then, and then the last thing to add was just, yeah, the wing stuff. So apparently the wing length also grew for 61 of the 77 species. That’s 79%. That’s not nothing and what they’ve said is that actually they see this effect more predominantly in the birds that spend their time higher up in the canopy. i.e the ones who are going to be, they going to be flying more. And it’s also going to be hotter and drier up there than it is on the forest [00:07:00] floor. So where it’s hotter, you’ve got a more pronounced in increase in wings. So, um, I think we, we did it again. We did that thing where we may be broke the planet and we changed all the animals.

[00:07:12] David: We did it. We shrunk the birds, honey.



[00:07:14] David: Sophie,

[00:07:25] Sophie: Ah, Dave, I’m so excited. Dave,

[00:07:27] David: I know you are.

[00:07:28] Sophie: I’m so excited.

[00:07:29] David: Researchers from the University of Cambridge have found a way to make sustainable non-toxic vegan and biodegradable glitter from cellulose to the delight of children, drag queens and I suspect Sophie everywhere.

[00:07:41] Sophie: Sophies everywhere. And Dave, not only have they done that, it is just as sparkly as the original.

[00:07:47] David: and they’ve made it from cellulose, which is the main building block of cell walls and plants and fruits and veggies.

[00:07:53] Sophie: Yeah. And so we wouldn’t like the cellulose that we think of, I guess, that we eat is, you know, we’d call it dietary fiber or something, [00:08:00] but basically it’s just, it’s made out of yeah, very non-threatening material they’ve made it to glitter at us it’s quite clever way that I understood. I understood conceptually.

[00:08:09] I tried to understand how you manufacture something like this. And I did not understand that

[00:08:16] David: I also try to understand how, and I also struggled to understand the how of the industrial process So they say this has been done before making glitter from something called cellulose nanocrystals. This has been done before, but what they’ve done here in this paper is to scale up the process to something that’s industrial, which is the exciting

[00:08:35] Sophie: Which is a really important step, because if we’re saying, look, the problem is when we normally make glitter, it’s often made of like toxic things. It’s not sustainable and it just contributes to plastic pollution. And especially now we’ve been talking about more about microplastics these days.

[00:08:48] So you’ve got these little particles of this like toxic, gross plastic, and then it gets ground up even smaller and then ends up in fish and stuff. And also the other thing that I didn’t realize that is just the amount of effort that goes in to [00:09:00] making normal glitter. So cause what they’re going to replace is the idea is, you know, you’re sort of your fun party glitter, but then also the little shiny things and stuff like makeup that may give you a flawless complexion, Dave.

[00:09:11] And, um, so, and so

[00:09:13] David: What are you, what are you implying about my complexion? That was very pointed.

[00:09:17] Sophie: That it’s flawless because obviously you must be using these up effect, pigment minerals in your, uh, your moisturizer in the morning.

[00:09:25] David: well, thank

[00:09:25] Sophie: why you’ve got such a flawless complexion, but yeah, apparently to make things like that, you have to heat them to temperatures as high as 800 degrees to form these pigment particles.

[00:09:35] And they also use things like mica and titanium dioxide, which are very bad. So apparently titanium dioxide recently banned in the EU for food application due to potential carcinogen effects, Dave isn’t, everything a carcinogen these days as a scientist, can you comment? Cause like you can’t even eat burnt toast anymore, you know?

[00:09:52] David: Yeah, well, there is a, there’s a newspaper, there’s an ongoing joke in the UK, in the media, which is that there’s a newspaper called the daily mail that is systematically dividing, [00:10:00] every substance known to man and to those which either cure or cause

[00:10:03] Sophie: cancer. Yep.

[00:10:04] David: and Yeah. so everything, well, I mean, I’m a pharmacologist, and the only difference between poison and cure is dose and that’s universally it’s universally true. So, take all of these things with a grain of salt.

[00:10:15] Sophie: That’s true.

[00:10:16] David: in addition to the carcinogenic things, apparently just in Europe, the cosmetics industry uses about five and a half tons metric, tons of microplastics every year.

[00:10:24] Sophie: I think it’s five and a half thousand metric

[00:10:27] David: Oh, did I see it? Yes. Sorry. Five and a half thousand. And you’re absolutely right. I neglected the thousands, which is about a thousand elephants worth, Sophie.

[00:10:33] Sophie: That’s too many elephants of microplastics, a single elephant of microplastic cause it’s too many, but, uh, that’s way too many.

[00:10:41] David: And what’s also cool. So what’s a cool science thing. Cause we should talk about the cool science then the cool science thing about this new glitter is that. So usually color in glitter and in lots of other things comes about from pigments and pigments are compounds that derive their color from their chemical nature

[00:10:59] right? [00:11:00] So by virtue of the chemical structure of the pigment, they’ll absorbed particular wavelengths of light and reflect other ones. And the reflected ones are the ones that you see because they’re not being absorbed. So something that absorbs all wavelengths of light looks black, something that reflects them all

[00:11:14] it looks white and something that reflects some mixture of them will look red or blue or yellow or orange or purple.

[00:11:19] Sophie: Exactly. But then, yeah. so this is amazing. So they use something called structural color, is basically, yeah, it’s not a pigment color thing. It’s a color produced by a microscopically structured surface that is fine enough to interfere with visible light. So we’re talking about like.

[00:11:37] The interference of light wave. So I think the best way to think of it. I don’t know. I think the thin film thing is quite, it makes it

[00:11:44] David: So

[00:11:44] Sophie: So of a bubble, like a thin bubble film, you know,

[00:11:47] David: Glitter and bubbles. Glitter and bubbles same article.

[00:11:50] Sophie: What an amazing week for science, everybody. Thanks. And also we should just shout out.

[00:11:55] This has come from the University of Cambridge. Finally, they’ve done something I care about. That’s not true they’ve [00:12:00] been very at a lot of things. and so, yeah, the idea is, you know, if you look at bubbles, you know, in your bubbles, you can see little rainbows in your bubbles, Dave., but bubbles and rainbow colored, they’re transparent. Right. You can see through them, but what you’re actually getting is you’re getting this iridescence because of the interference. And it’s got to do with the refractive indices of the different materials.

[00:12:18] So a thin film of bubbles and you got white light traveling into it. And then basically you can get some light that’s reflected off and then you’re going to get some lights that travels through, but because the bubble is like a different density, you know, there’s lots of different things happening, but the bubbles are a different density to the air.

[00:12:33] It means that when the light goes through it, you basically get a bit of a shift. And so sort of, you know, you get light bending. It’s like when you’re in the swimming pool and you look at your body and then you look at your body underwater and it kind of looks like you’ve got some strange angles happening. It’s varied. It’s obviously it’s deeply upsetting. It’s the same thing. So you have light traveling like a different distance and then that’s going to come out. And then, you know, we’ve talked about constructive and destructive interference, but you can basically, you’re going to get some waves.

[00:12:59] Wavelengths canceling [00:13:00] out some of them reinforcing and basically, yeah, you end up seeing all these different colors. So what they’ve done is back to our cellulose glitter, they’ve managed to make this magical cellulose thin kind of, it just looked like a big thin sheet of plastic that just like was shiny in different colors that then they just crush up into like really small little particles and then that’s the glitter, but they can do, what I read and I, this is what I couldn’t work out.

[00:13:25] They did it, they can tailor it to any wavelength, which means they can produce any color imaginable on the visible spectrum. They can make any colored glitter ever.

[00:13:38] David: Yeah, I didn’t understand it. There was something about a color story. Matrix or something that and that had to, yeah. Okay. I’ll read it. I’ll read the thing. And so the reader can see what they make of it. So an aqueous cellulose nanocrystals suspension was deposited and subsequently dried on top of a moving polymer, substrate. Okay.

[00:13:58] cool. Before being [00:14:00] delaminated for further offline processing and to structurally colored cellulosic microparticles, I mean,

[00:14:05] Sophie: Yeah.

[00:14:08] anyway, but there was a picture in the paper of little jars of different colored glitter, and they’re beautiful and they’re very, very shiny and I love them. And the fact that, yeah, well, as you mentioned before, this is really important. Cause what they’ve managed to do is take this process that we’ve been able to do on small scale before, and they’ve been able to use available commercial machines to do like proper,

[00:14:30] you know, commercial scale production of this stuff. And so I think that’s where, you know, we often, when we talk about stuff on STEMology,, you know, it’s in the first stages of this as, you know, a proof of concept or whatever, and they’ve gone, like we have taken this and we have upscaled it and you can use these big, what are they called?

[00:14:47] Roll to roll machines. Like the things that you made on paper for. From, you know, using wood pulp, these big rolly things, it looks like a

[00:14:56] newspaper printer thing, you can make, get these big [00:15:00] sheets of colorful cellulose that then you can basically like grind up into glitter. It’s just.

[00:15:07] David: they’ve done great work. And apparently it will be just as annoying as conventional glitter. but It’s just.

[00:15:11] biodegradable

[00:15:13] Sophie: I, yeah, so it was, it was, vineyard, Leni, one of the people involved and I’ve wrote that quote down, it’s like the talking about how great it is, blah, blah, blah. And they’ve gone. It will be just as annoying, but it won’t harm the planet and it’s safe your little ones. And I’m like, what a quote like we did this amazing thing.

[00:15:26] It’s going to be a pain in the ass, just like normal glitter. It gets everywhere. Once you spill glitter, you can never unspill glitter. But at least it’s all biodegrade. and it’s, you know, safe to eat. Oh safe to eat.. That’s exciting. Maybe that’s how they make edible glitter. Dave, I’ve not thought about that because you can get edible glitter for cakes stuff.

[00:15:43] I wonder if it’s just really expensive and they do it online, you know, a small scale kind of production and a booklet, or I don’t know.

[00:15:50] David: Maybe, I don’t know either. presumably it doesn’t involve carcinogenic unsustainable or an ethically sourced competence.

[00:15:56] Sophie: I don’t think, I don’t think you let us sell it, that a glitter, if you know that it’s [00:16:00] carcinogenic. I

[00:16:00] think I think we have enough law within Australia to prevent that kind of stuff, but yeah, no, I thought that was great. in my later life, I have fallen in love with glitter as a child. I think I did like glitter, but as an adult, I was just really, it’s really dawned on me how spectacular

[00:16:13] and

[00:16:13] shiny

[00:16:14] David: you ever use that site that was glitter bomb, your enemies or something like that? That was that like glitz or your enemy? I can’t remember what the

[00:16:20] Sophie: I didn’t, but that was one that I really wanted to use. And I’m going to bleep some words, but it was code eight, a bag of something starting with D . And what you could do is you could, um, send people little bags of gummy, something starting with a D.

[00:16:33] David: That’s still the thing. it’s chip a D.

[00:16:36] Sophie: Oh, okay. We’ll say, I think this one was called, but then one of the options was you

[00:16:40] then feel this with edible glitter so they can still eat their bags of D,

[00:16:46] but like when they open it, they were going to get glitter. So it’s like the best of both worlds. So not only your glitter bombing someone, you’re also telling them to eat a bag of D as well. I was going to send someone once, but at the time I was a student and I couldn’t afford it. [00:17:00] So.

[00:17:01] David: It’s a

[00:17:01] Sophie: I could do it now,

[00:17:02] David: We can do it now.

[00:17:04] fully

[00:17:05] Sophie: write into stem ology. You’d like me to perpetuate a grudge that has been going on for many years, but you know, I great work. I think, you know, I love the fact that we’ve scaled it up, and I think in fact, the researchers are going to turn this into a little side hustle,

[00:17:19] David: Spin out companies on there. Fund the research, it’s what you’re supposed to

[00:17:23] Sophie: It’s great. So everyone, Get ready to bring glitter back into your lives in extreme way. Courtesy of the University of Cambridge.

Maybe-dead-toothed frogs

[00:17:30] Sophie: Dave biologists have laid to arrest a century old debate by confirming that a single species of frog has true teeth on his lower jaw, but also that frog might now be extinct.

[00:17:53] David: Yes, So we got excited because it was a single species of living frog, but it may not be living anymore.

[00:17:59] Sophie: [00:18:00] Living, but we’re not quite sure just cause people haven’t seen it for a while, but yeah. So this is some work at the University of Florida and we’re talking about a large marsupial frog, which I love and we can get into because they didn’t know be marsupial.

[00:18:12] do we think it’s Gastrotheca or Gastrotheca do I

[00:18:15] David: I was thinking Gastrotheca

[00:18:17] Sophie: Thika Theca Gastrotheca Guentheri. Do you know what let’s call a let’s call it a GG. That’s a cute name.

[00:18:23] David: Call it, GG. . I love

[00:18:24] Sophie: GG. so basically this large marsupial frog GG has puzzled scientists since its discovery in 1882 for possessing what appeared to be a complete set of Jagger dagger light teeth on the top and bottom of its mouth.

[00:18:38] So apparently Dave, I didn’t know this about frogs. They’ve got lots of different insights of their mouth. Some frogs don’t really have any teeth at all. They’ve just kind got like sticky tongues and stuff. Others have like a row of teeth on that upper jaw. And then they also can have things like a toothy cerated palette on the top of their mouth to sort of keep the wiggling prey in place.

[00:18:58] You’ve also got, in rare [00:19:00] cases, frogs that have large bony fangs that protrude from the lower jaw and they resembled teeth. But. They lack the telltale dentine and enamel tissues that teeth need. So this is this whole issue. So we’ve got this frog that looks like it’s got top and bottom teeth, but there’s a lot of frogs that look like they have teeth, but they’re not true teeth.

[00:19:18] The problem is that they’re very small and we weren’t able to actually confirm the existence of these enamel and dentine to tell we have one species of frog that might still live, that actually has true teeth on a bottom jaw. That’s clincher, right?

[00:19:33] David: and I think, yes, I think that’s the clincher. And I think this is of interest and correct me if I’m wrong it’s of interest, because at some point, presumably there was an ancestor of all frogs that had teeth. And then the frogs lost those teeth, they had true teeth. So there was an ancestor frogs that had true teeth.

[00:19:50] Frogs went on to lose teeth either on the top or the bottom or both. And then they’ve re-emerged and there’s this law called Dollo’s law, which states [00:20:00] that an evolutionary trait once lost can re-emerge in the same form, it will bear, telltale signs of the intermediate steps. So what’s striking about this is that it’s the re evolution of teeth, which as you say, have dentine and enamel and are very, very tooth-like in an animal, which has previously lost them, which is supposed to be against the rules.

[00:20:20] Sophie: Yeah, so, and it says, I found a weird thing in this, so yeah, apparently original frog fossils from 200 million years ago. Those frogs lacked teeth.

[00:20:30] Right. Then though, apparently. They got, as you said, so the frog basic body shape and anatomy has remained largely unchanged since the Jurassic period, but at one stage, the frogs then had teeth, but apparently, Dave, they have lost teeth on more than 20 separate occasions, regained them six times throughout their evolutionary history.

[00:20:51] And now what we have is this one frog that might still have the bottom teeth, but you’re right. Like this whole is like crazy in terms of Dollo’s law because it’s that [00:21:00] idea that, you know, if you lose that complex trait in an organism, like, you know, you’re not going to get it again.

[00:21:04] David: Yes. And they say that this is evidence that there’s maybe a simple switch, a simple genetic switch, which can turn teeth off and on. And they relate that to one that’s similar in birds, which is called. So in birds, there’s this thing called BMP for Bone Morphogenetic Protein 4 which is very, very important in two things.

[00:21:23] One is like, bead shape So, if you, the way that it’s expressed affects your beat shape very much, but also apparently it causes the birds to have, or to lack teeth. so, but it’s basically, it’s a single gene that kind seems to regulate this, whether you have teeth or not. and basically they say, and there’s another one apparently in turtles called MSX two, which does something similar in turtles.

[00:21:44] So they say this fact it’s re-emerging, I presume it’s the saying that this regulates whether or not the turtles have teeth. so basically the saying, so the fact that the teeth have come back and look very teeth- like suggest that maybe there’s a simple genetic switched on and off that gives the frogs their teeth back.

[00:21:59] Sophie: Yeah. And [00:22:00] so I think that, the reason that this is, an impressive study is because they’ve actually finally managed to test the teeth, to work out that they are true teeth.

[00:22:08] David: They looked by looking, they tested it by looking, which

[00:22:11] Sophie: But they also, Dave, I believe that they did some slightly fancier things in some cases where they carefully stained razor, thin sections of the teeth with dyes that only bind to things like enamel and

[00:22:21] dentine. but yeah, those, like some of the pictures weird me out and yeah. So I think part of the issue was they haven’t seen, so this frog usually hangs out in the cloud forest of Columbia and Ecuador, but the last recorded observation of GG was in 1996. So that’s why we have now this fear that maybe she has to come to extinction and they do have a handful of these things sort of preserved in museums, but because of the rarity, like they didn’t want to mess with them. Right.

[00:22:46] Because often if you do like teeth analysis, like in this one where you have to take rays of thin sections of teeth, you’re really destroying, you know, an important specimen. So they use preserved embryos as a sample rather than the full adult. And [00:23:00] there’s some real gross pictures of just in the paper, just a frog embryo in a sack.

[00:23:05] David: we should mention briefly. So again, GG is a marsupial frog and so-called because they have a dorsal bridge pouch. So dorsal means on the stomach. I did you read

[00:23:14] Sophie: Doesn’t it mean on the back? Isn’t isn’t a dorsal fin on a back

[00:23:17] David: Oh, no, yes. The dorsal. Yeah. Yeah. You’re right. It’s the backs, but yeah. Dorsal as

[00:23:21] Sophie: that’s all I know about sh

[00:23:23] David: arks, Dave.

[00:23:23] Yeah. Yeah. so, and apparently in some species of marsupial frog, the eggs are fair to lies on the females, lower back and inserted in her pouch with the aid of the male’s toes.

[00:23:33] Sophie: Oh, that doesn’t sound sexy. at all.

[00:23:37] David: Likes to get weird with it.

[00:23:38] Sophie: GG got a foot fetish. that’s not okay. But yeah. So the idea is that these frogs, then they skip that tadpole stage that you know is important. Cause I believe, you know, when you’re tadpole, you really like to breathe in water. And I guess if you hit sitting on someone else’s back and you’re a tadpole, you might air-drowned. What is, what do you call air drowning?

[00:23:58] David: Suffocation.

[00:23:59] Sophie: Yeah, you might [00:24:00] suffocate and that’s good air-drowned,, all the latest high quality science going to you from STEMology. Anyway. they skipped tadpole stage and then they directly turn into these, the miniature versions of the adult frogs called froglets. And so they did their CT scans on the embryos jaws, and then they did this thing the different staining and stuff, and they found that the teeth were virtually identical to those of others frogs.

[00:24:22] Or other frog species in overall shape development and also the tissues. That’s very good. So we’ve said that the frogs that we know have top teeth, these bottom teeth had just like the top teeth, hence they have teeth.

[00:24:32] David: Yeah. that was my understanding too. And they also say, they saw a successional dental on both the upper and lower And that’s interesting because that’s the means by which the tooth, the teeth are replaced. If they’re lost.

[00:24:44] That’s kind of like probably people will be most familiar with a shark where there’s like, the rows of teeth are coming forward.

[00:24:50] So not only did they see teeth, they saw the precursors of new teeth

[00:24:54] Sophie: New teeth for the teeth.

[00:24:56] David: And I wonder if, do you think they worked on froglets? Maybe the froglets are less valuable [00:25:00] because there are numerous. So like,

[00:25:02] how many they make, but like, you make a lot of tadpoles all at once.

[00:25:05] Don’t use. So maybe you make a lot of froglets all at once, so it’s not so.

[00:25:08] Sophie: yeah, I presume that cause they’ve, they just seem to have preserved embryo So, I guess they just ain’t. Yeah. Whereas they, you know, they had full-size adult samples as well, but they didn’t want to mess with those. So I presume that yeah, it was just, less valuable. Yeah. You’re right. And they went, okay, we’ve got a bunch of these embryos.

[00:25:23] Let’s look at their teeth

[00:25:24] gross And they have it. But yeah. So there is one, there was one species of bottom tooth frogs, might be dead, not sure. Look, if anyone sees GG, if anyone’s hanging out, in the Colombian and Ecuadorian cloud forests, and they see Gigi drop us a line at Stemology@ramaley.media we’ll, uh, pass on the message to the university of Florida.

Special Neurons

[00:25:48] Sophie: Dave, tell me everything you [00:26:00] know about neurons and more, but specifically about maybe the number of, ion channels in different mammals.

[00:26:06] David: That’s a very literal segway that I appreciate very much. So neurons our brain cells and they communicate with each other via electrical impulses. Right. So the way that cells work, and I’m just going to explain this briefly, cause it’s important to what we’re going to talk about. The way that cells work is that they charge themselves kind of like little batteries.

[00:26:24] Right? So if you imagine a cell that’s round. Got an electrical imbalance across its membrane. So the cell expends energy to move charged particles called ions into the cell. And the reason it does that is because if it opens up some ion channels and rapidly lets the charge equilibrate. So if it rapidly leaves the charge and dissipates.

[00:26:44] So battery discharges that causes changes on the inside of the cell to proteins and the cell can signal very quickly. So this is a very advantageous thing for cells to be able to do. Right. What neurons do when they discharge is they send electrical signals largely to other [00:27:00] neurons. And this is if you do this with 86 billion neurons inside a head, somehow the connections between them makeup you, and that’s a living thinking happening brain.

[00:27:09] So this building up of charge and the sudden releasing of charge and neurons is basically what makes the brain go in a very, very fundamental

[00:27:17] Sophie: I know Dave, I want to use my, my one piece of knowledge about brain. Is that chain reaction? Is that the action potential?

[00:27:25] David: That’s the action potential. So when you send an electrical impulse from one end of a neuron, neurons are weird among cells because they’re not round. They tend to be kind of long. They’ve got a kind of cell body that’s kind of, you know, triangular in shape often. And then it sends off these long legs and the long legs speak to other neurons speak they speak to something else.

[00:27:45] So one of the whole advantages of having nervous system is that you can transmit information to distant parts of the body very quickly

[00:27:51] Sophie: Yeah.

[00:27:51] David: So basically this story this week is about a fairly fundamental finding, which is about the number of ion channels on human [00:28:00] neurons versus neurons from other species. So basically what they say is they looked at a number of species that, and specifically they looked at a number of species as they went from very, very small up to very, very large up to human sized.

[00:28:14] So they started with the Etruscan Shrew, which is one of the smallest non-mammals through gerbils mice, rats, Guinea pigs, ferrets, rabbits, marmosets, macaques, and then humans,

[00:28:23] Sophie: It’s basically everything you want as a pet except for the human, I reckon.

[00:28:27] David: basically. Yeah. Well, I guess that’s having children, but I mean, it’s.

[00:28:30] Sophie: Oh, that’s true. Yeah, they do have pet people don’t know.

[00:28:33] David: It is just, it’s an increasing level of responsibility. It really isn’t it?

[00:28:36] Sophie: Yeah. I think you’re right. I know. You’re you might be right with that list of pets. I mean, should say a lot of them illegal in Australia because of biosecurity law, but you can have some of those in Australia.

[00:28:45] David: Well, there’s a lot of responsibility involved in that instance. So basically what they found is that as generally speaking in all other species, as the animals get bigger, their neurons get bigger as well. And not only do the neurons get bigger because the surface, we talked about [00:29:00] surface area to volume ratio earlier in the episode with regards to.

[00:29:03] So, this is also true for the movement of electrical charts and important property for the movement of electrical charge in a neuron. So as the neurons get bigger, the density of the ion channels. So the number of ion channels per unit area on the neuron also tends to get bigger, unless you’re a human, the human has way less.

[00:29:23] And

[00:29:24] Sophie: Yeah, it’s crazy. So basically for all the other mammals for your given volume of cortex or wherever they were looking, the energetic cost is the same for

[00:29:32] the channels in every the nine mammals that weren’t people. And then the people it’s just yeah there’s this rapid drop.

[00:29:39] David: Yeah.

[00:29:40] So they said, this is really weird. It’s really weird that the number of ion channels goes up for the size of the neuron. But then they say, if you look at the overall cortex size, as you say, the overall, they’re basically saying the number of ion channels in the cortex of all these animals is roughly the same.

[00:29:54] The roughly the same, which is kind of weird to me as a neuroscientist because.

[00:29:59] Sophie: [00:30:00] Okay.

[00:30:00] David: I wouldn’t say that the number of ion channels, the ion channels are had, the charge has moved, but I would be much more likely to say that it’s how the neurons are wired up. That produces the function, the neural function, to the number of ion channels and energy expenditure is going to be really important because the brain uses a lot of energy and energy use is key to your survival as an organism.

[00:30:22] And that will be important, an important influencer, but as the function, the number of ion channels would seem to be, you know what I mean? You see what

[00:30:29] Sophie: It’s interesting. Cause I came up from a mathematical point of view being like, well, that seems like a very sensible scale up. Like we’re keeping the density the same in everything. I was like. Yeah. Well, I mean, what a great result that seems, you know, what a sensible evolution that we have

[00:30:42] except for people.

[00:30:43] David: Yeah. So basically what they say is whatever, the reason, if, if this holds true and the overall energy expenditure scales up fairly linearly with the size of the neuron and therefore the size of the animal. Basically if human beings have less ion channels, they’re expanding less energy to move charge in and out of [00:31:00] the cell, which means they may be using that energy to do something else they say. So they may be using the energy to form more complex synaptic connections with neighboring cells. They may be using it to increase the rapidity with which they can fire action potentials, and that might have important functional consequences.

[00:31:16] they’re not very sure, but this seems to be the take home message that we have. More energy, efficient neurons that are, even though they are very big, have fewer ion channels per unit area.

[00:31:28] Sophie: Now, Dave, I’ve got some questions for you that you may or may not be able to answer because you know, way more about this than me. And as I said, I know, a tiny little bit about the action potential just because my honors thesis is on mathematical models of neuron firing. And I know that all the modeling they did was based on animals because obviously that’s what we did.

[00:31:44] You know, we’d still do. We still do it. You can’t do things on people. Dave, the ethics is just out of control.

[00:31:50] So like the main mathematical model of neuron firing as a Hodgkin Huxley model. So those two guys Hodgkin and Huxley, I think, I think they did their [00:32:00] model and it was the early fifties.

[00:32:01] It was like 52 or something, but they want a Nobel prize for it in like 63, I think. And they basically, they came up with this very complicated model for the action potential using like a giant squid axon, And then a lot of people have done dimensional analysis, which means that they’re just taking like the very complicated method set of mathematical equations.

[00:32:19] And they’ve made them a little bit simpler to look at certain things. So like is like another very, very common one in math. And I think that’s like simplified Hodgkin, Huxley, but then there’s like the Morris-Lecar , which was, they did it using a giant barnacle. All of my questions is like, Do you know, if we use those models to actually draw conclusions about people, like, is it bad that all of our neuron firing models and now based on animal models that were, I mean, granted, I guess a giant squid in a barnacle aren’t mamm als and we didn’t test things in not mammals, but.

[00:32:53] David: I guess things, so your answer, I don’t know the answer to your question, but, but I can speculate a little bit. So this is a biophysics [00:33:00] paper and which means I didn’t understand the great suedes of it.

[00:33:03] Sophie: Oh, you can tell. I definitely, if you didn’t Dave, I was reading a different language,

[00:33:08] David: But what I can tell you is, so you can’t really do experiments on people but really when you do experiments on whole organisms, you’re interested in the function of the whole brain. let’s say you’re interested in a behavior. You might be trying to pinpoint a group of cells in the brain that influence that behavior and show that if you switch them on and off, then you remove the behavior or emphasize the behavior or something.

[00:33:28] So in those kinds of studies, you can’t use a human being because. You can’t, but in those kinds of studies, you’re also interested in the whole brain, the function of the whole brain. And what they’re looking at here is really single cells and you get single cells. So it’s actually, again, this is a pretty fundamental sounding finding, but also the way that they did it was pretty good because they actually did what it’s called electrophysiology on neurons.

[00:33:53] So this is when you take a very, very fine pippette. Like a glass pipette. So pipette is just a point, your piece of hollow [00:34:00] glass

[00:34:00] Sophie: Yep. A socket. it’s a tiny Turkey baster.

[00:34:03] David: it’s a tiny turkey. That’s exactly what it is. It’s a tiny Turkey baster Phillips salt solutions. And what they’ve done here is they’ve poked a neuron and a neuron is very, very small.

[00:34:13] So this is very, very difficult people. And then they’ve done, what’s called outside patching, which is a kind of basically what you do is you pull off a little piece of the cell’s membrane. and it’s so small that there’s a chance that when you do this, that you get a single ion channel or single, or just a few ion channels.

[00:34:32] And by changing the composition of the salt solution that you’ve got, or by changing the voltage insight, The Turkey baster, you can then cause ions to move in and out of your electrodes and you can record the changes in either current or voltage.

[00:34:48] Sophie: very clever.

[00:34:49] David: Yeah.

[00:34:49] So they’ve actually done this by looking and they’ve actually done this by looking in human cells, which I presume mean that they don’t have to model it per se. They can [00:35:00] look. When you’re doing cell stuff, you can look and people do this. Like people do crazy things. They’ll do patch clamping. So this kind of patch, clamping electrophysiology at more than one place on the same neuron sometimes, which is just like, it sounds like nothing.

[00:35:15] And there’s no context in this podcast, but like that’s hours of work, Years of expertise and hours of work, just to set that up and then to do the experiment, which is very, very hard. Electrophysiology is something I used to do, and it’s very, very hard

[00:35:28] Sophie: no, I believe it it’s. Um, anyway, it seems significant, Dave, I feel like you’ll understand the significance more than me, but it’s like, there you go. We’ve just got small number of ion channel.

[00:35:37] David: on our big, great big neurons.

[00:35:38] Sophie: On a great big neurons just because we might be using our great big brains neurons for slightly different things than other mammals.

[00:35:47] It’s why we’re in charge.

[00:35:49] David: Yep. So we have podcasts.