True Facts: Frogs That Hide Their Blood

If you want to hide in plain sight, there's a couple ways to go about it. You can commit to a body that looks like what's around you, but good luck if you want a change of scenery. You can do the octopus thing and match your background on the fly, but who the f**k knows how to do that except the aliens that brought them here. Or transparency, right? Let the background pass right through you. Low effort, works anywhere, seems like a shoo-in. But there are some hurdles to overcome. Light moves through things at different speeds. A measure of how fast is called a refractory index. If you're made of something with a very different refractory index than your surroundings, light will change direction or scatter when it passes through, causing the background to distort. And then you can be see-through but still seen, see? Now, things that live in water have a leg up on this, because the refractory index of water is close to living tissue, which is also mostly water. And there's a number of creatures that do it down there. This nudibranch is pretty impressive. The glass shark here, which is almost impossible to see because it's bulls**t and I just made it up. But anyways, even in water it's not that simple being transparent. Anemone shrimp, for example, can take some eye rubbing to focus on. But things start to fall apart if they get too much exercise from flipping that little tail about. When it does, its transparent abdominal muscles get flooded with its transparent blood or hemolymph. And that causes enough differences in the refractory indexes of that area that light scatters and screws up the see-through-nessness. And then, of course, you have all the classic invisible man problems. Here's the water flea Daphnia showing off the food-slash-poop invisibility paradox that's a staple argument for 10-year-olds everywhere. Not that much you can do about the poops you would accept not eat, but they can do something about that eye. Daphnia that live in water where there's a lot of fish about have smaller eyes, which seem to help them avoid detection. And it does seem like being partially or mostly transparent still helps to avoid a predator. The glasswing butterfly, for example, has some of the most impressive transparency of a land animal. Those transparent parts still have scales on them, by the way, which they need to shunt water. But look, they're reduced into little pool noodles. Denser pigmented scales near the edge of the wing absorb light and are dark, which you'd think would screw the whole thing up. But it's been shown that the package is enough to reduce predation. Now, the glass frog is more like a stained glass frog. It's a bit of a stretch to call it transparent. Certainly translucent. I mean, for one thing, it's green, which isn't terrible since it spends 99. F**k it, all of its life on a green leaf. So it doesn't really need to worry about changing colors or textures. But the partial see-throughness does help with blending into how light or dark the background is. And the slightly more see-through extremities, like its legs, can make it hard for a predator to figure out where the leaf stops and the food begins. However, the glass frog has its own version of the invisible man problem. Blood. Red blood cells are very good at absorbing light, which means you can see veins but also a big-ass beating heart, which is like a bullseye for a predator. When they're awake, there's not much to do about it, but they're aware and can still escape if detected. But when they sleep, they're especially vulnerable. And they have a trick. Their red blood cells move into little pockets in their liver. They hide. And this makes them two to three times more transparent than when they're awake and exercising. It doesn't work if you anesthetize them, by the way, so you'll still see a drunk frog. Only when they go to sleep correctly. And then when you wake them back up, red blood cells come back out to play. And that's the deal with superpowers. There's always some crap you have to deal with you didn't think about. You gotta hide your blood cells. It's bulls**t. There's a free and easy way to learn more about refracted light and all sorts of other things. Brilliant.org helps you learn more about math, science, and computer science interactively. Let's face it, being an adult is basically improv. Just not the funny kind. Brilliant gives you the tools to make the most of all the crazy things that life throws at you. Could be a new job opportunity, or a child that wants help programming a Minecraft mod. There's thousands of courses, and Brilliant customizes them to your interests and skill level. You can learn about math or how to code. Me, I like the data science stuff. Especially learning about how misleading certain presentations of data can be. If you've been thinking about learning and want to try something that's fun and interactive, but also effective, then Brilliant is a great gift that you can give to yourself. To try everything that Brilliant has to offer, free for a full 30 days, visit brilliant.org slash ZeFrank, or click on the link in the description. The first 200 of you will get 20% off Brilliant's annual premium subscription. And you'll be supporting a brand that helps make this show possible. Try Brilliant today. Where were we? Oh, right. In terms of superpowers, you'd think that the boa constrictor has it fairly straightforward. Squeezing power. It's just one of those awkward hugs that goes on for too long brought to its logical conclusion. Just coil the first 30 of body around something and then squeeze it so tight that it can't breathe. Simple, right? All right, well, while it's doing that, how does the snake breathe? God damn it! F***ing fine print. They had to figure that one out. Let me explain. Now, snake insides get a bit weird. They got to cram it all into that tube. Look at that. It's got staggered testicles. Put on a blindfold and try to miss, you'd still kick a snake in the nuts. You know what they call this? An anal scale. I'm not googling that. Don't even want to know how much mine weighs. Anyway, these things up here are the lungs. The left lung, if they even have it, is just a little janky stump. But the right lung here goes down a third of the way. So their lung is right under the part that they use to squeeze. Now, to get around this and not black out every time they have lunch, boa constrictors have evolved ribs that can move independently. Look at this. You put a blood pressure cuff around one section of the lung and an area farther back takes over the breathing. If you put the cuff on the farther back spot, the front takes over the breathing. And look, the section in between isn't moving. These are like breathing zones. And you can actually see this in action when a boa captures prey. The mouse here is already dead. After about three and a half minutes of squeezing, you can see that the snake has moved its breathing to two sections in the back. As it starts to release, a pretty long section comes back online. And here's the thing. When it's done with the constriction and starts to swallow its prey whole, it also has to move where it breathes from because now the prey is exerting pressure from the inside. And in fact, it's thought that this ability evolved first as a means of swallowing large prey, which only then allowed snakes to evolve constriction as a form of hunting. And yes, I just made you yawn, mother****er. No? Not yet? All right, we'll wait. The velvet worms split off from the arthropods about 500 million years ago. Now, they've been evolving just as long as the rest of us. But at first glance, it might not look like they've been using that time all that effectively. Just doesn't look like they've got that much going on. Here's one shown to scale in an unnecessarily threatening way. But anyway, you know what they've been working on for 500 million years? Spider-Man, basically. But like real and without the movie franchise. And let me tell you, to get there, they had to do quite some creative problem solving. Now, the velvet worm might look like a Muppet caterpillar, but it's quite complex. It just does things its own way. Like walking, for example. Velvet worms are basically fluid-filled sacks. No skeleton, no joints, but plenty of muscle. To move a pair of those inflatable legs, it squeezes and elongates a body segment which lifts the legs and swings them forward. Repeat that in a wave down your body and you're off to the races. Looks like you got a little TP stuck to a heel there. Now, it seems like what happened is that a pair of these legs up front evolved into those slime cannons. And here's roughly how it all works. Here's the inside of the velvet worm and you can see its slime glands. Very pretty. The slime is secreted up in the shaggy bits there and then it's stored down in the reservoir, which is French for reservoir. The reservoir is surrounded by a muscle and it's a cool looking muscle too. All criss-crossy like a reinforced radial tire. And the job of this muscle is to squeeze the slime out. The problem is, velvet worm muscles can't contract all that quickly. So without a little help, the slime would just come out like a dribble. Think Spider-Man with leakage. But as anyone who's melted a pin into the top of a shaving cream can on Halloween knows, a small enough hole can turn a dribble into a squirt. With dist, this sounds like pornography. Anyways, that's what they do. The slime is squeezed out of the reservoir and into this funnel, which ends in one of these modified legs or papillae. And then it shoots out the little hole at the end of it. But if you look at the slime, it doesn't come out in a straight line. It's all over the place. That spreads it out and totally covers that giant paintbrush of doom. And it does this by moving its papillae back and forth really fast. Actually, too fast. They move about 20 times faster than their muscles can contract. And the way they do this is by harnessing floppy power. All right, so if you take a floppy tube and pass fluid through it, at low speeds, the fluid comes out straight. But as the fluid moves faster, there's a point at which the tube becomes unstable and the whole thing goes wonky. This is like a runaway garden hose. So in real life, Spider-Man doesn't have so much of a precision shot. It's more of a... And you know what? The velvet worm slime is water soluble. They don't tell you what happens to all the webs in Spider-Man. There's probably some dude that he hires to follow him around with a mop. Can't just let it sit there. It starts to stink.