Spider sense

ROWAN: You're listening to Brains On--

DYLAN: Where we're serious about being curious.

[MUSIC PLAYING]

MOLLY BLOOM: Spiders are arachnids.

ROWAN: They have eight legs.

DYLAN: And two body parts.

MOLLY BLOOM: A cephalothorax and an abdomen.

DYLAN: But not all arachnids are spiders.

ROWAN: Some are ticks or mites or scorpions.

MOLLY BLOOM: So what makes a spider, a spider?

DYLAN: It's all about their silk and their venom.

MOLLY BLOOM: We're going to answer your questions about spiders and their webs right now.

BOTH: Keep listening.

MOLLY BLOOM: You're listening to Brains On from NPR News in Southern California Public Radio. I'm Molly Bloom. I'm here with two co-hosts today, brothers Rowan and Dylan from Roseville, Minnesota. Thanks for being here.

DYLAN: Hello.

ROWAN: Hi.

MOLLY BLOOM: Are you guys afraid of spiders.

ROWAN: No.

DYLAN: Yeah, I'm not.

MOLLY BLOOM: You're not. Why not?

DYLAN: I think that once you start to learn about the spiders, you see that they're actually not that scary. Like you're scared of them because they look so different from everything else. But if you learn about them, they're different in a cool way.

MOLLY BLOOM: And do you have a favorite thing about spiders?

DYLAN: Their legs.

MOLLY BLOOM: Why?

DYLAN: Try to imagine you walking on eight legs. It would be like really hard. I would think that I would be like tripping over all of my legs.

MOLLY BLOOM: So you're just impressed they can do it.

DYLAN: Yeah.

MOLLY BLOOM: Our listeners favorite thing about spiders is clearly their ability to spin silk and make webs. Because we've gotten quite a few questions about how spiders make that cool material and those intricate structures--

DYLAN: We talked to Anthony Auletta to find answers. He studies spiders at the University of Minnesota.

ROWAN: We began with a question from Samuel in Austin, Texas.

SAMUEL: I want to know how spiders spin and make their silk.

MOLLY BLOOM: Anthony told us they use a special structure that only spiders have.

ANTHONY AULETTA: There are these little tiny finger-like structures on the abdomen called spinnerets. Most spiders have six. And if you look at them underneath a microscope, they're covered in tiny, tiny, tiny little holes. And the spider makes the silk inside of its body, inside the abdomen.

And when it's ready to spin silk, it will actually push it out through the holes in the spinnerets. And then it can wave its spinner around to weave the silk in whichever shape it wants. Actually, it's very fascinating because spiders can actually make many different types of silk.

They can make silk that's extra stretchy. They can make silk that's not very stretchy, but extra strong, depending on what they're going to use it for.

And some spiders can actually make several different kinds at the same time, and then use their spinnerets to kind of weave it together to create a hybrid, which I think is really cool. There are other animals that can spin silk, but none of them spin silk through spinnerets like spiders do.

MOLLY BLOOM: Our next question comes from the capital of the Netherlands.

SPEAKER: My name is Etim. My question is, how does spiders stick to walls and webs?

MOLLY BLOOM: When spiders spin silk, they actually deposit little droplets of glue on the fiber to make it sticky.

ANTHONY AULETTA: Whenever an insect flies into the web, it's going to get stuck to a bunch of different glue droplets. And as it struggles, trying to get out of the web, inevitably, it's going to hit more droplets and get more stuck.

Not all spiders do it that way. There's a small group of spiders, the cribellate spiders, as they're called, which spins silk that isn't sticky. Instead what they do is they draw the silk against the little plate that they have. And that makes it frayed, kind of like wool fibers. There are lots of little bits and pieces of fibers everywhere.

And when an insect hits that, its little legs and its wings get tangled in those fibers. And as it struggles to get out, it just tangles itself even more.

DYLAN: If spiders use the glue method, they have to be careful not to get stuck in it themselves.

MOLLY BLOOM: Before we find out more about how spiders use silk and spin their webs, we have an important public service announcement to share with all you arachnophobia.

DYLAN: That means someone that's afraid of spiders.

WANDA WOLF SPIDER: Hi. I'm Wanda Wolf Spider. Are you afraid of spiders? If you are, you're not alone. It's the third most common fear or phobia in the United States. But I'm here to tell you that spiders are here for you.

Let me ask you something. Do you like pests around the house? Like mosquitoes and cockroaches. Well, I do. They're delicious. Lots of my spider pals like them too. And we help keep the pest population in check by eating them. Fewer mosquitoes for you, and more delicious meals for us. I'd call that a win-win.

So next time you see a spider in or near your house, maybe try not smushing us. Give one of our eight arms a high five. If that's asking too much, we'd settle for just the not smooshing part.

SPEAKER: (SINGING) Because spiders are your friends.

DYLAN: Now let's get back to that spider silk.

MOLLY BLOOM: Spider silk has all sorts of cool uses. It's not just for webs.

DYLAN: Some spiders don't even need webs at all.

ANTHONY AULETTA: So not all spiders spin prey capture webs to catch their food in. Some spiders are active hunters. They don't spin a web. They kind of crawl around on the ground or on plants, and will actually seek out and pounce on insects. So they don't need the web.

But every single type of spider uses silk in some way. One thing that all spiders use silk for is constructing egg sacs. So spiders can lay hundreds of eggs. And they take all their eggs, and they wrap them in this very thick ball of silk called the egg sac. And for this, they don't need silk that's very stretchy, but they need silk that's very, very strong.

There are many other uses for silk. One really interesting one is this phenomenon called ballooning. So after the spiders hatch from the egg sac, they need to go somewhere. They can't all live in the same spot because they might get eaten by their brothers and sisters, which is a problem that spiders tend to face, because they're cannibals.

So what a lot of baby spiders will do is they'll climb up to some tall point, like a branch or a bush or a leaf, and stick their abdomen in air and just release a little strand of silk. That silk will get caught in the wind and take the spider large distances, somewhere, where hopefully, there will be a lot of food, but not a lot of other spiders to compete with it.

And there have been reports of ballooning spiders crashing into windows of airplanes, and getting carried across the ocean to islands. In fact, when new islands form, like a volcanic island, for example, one of the first types of animals to reach that island and colonize it are actually spiders. Because the young spiders are carried there on these silk and balloons.

ROWAN: Spiders can also use silk to help them climb.

DYLAN: And spiders at burrow use silk to line their tunnels and keep them waterproof.

MOLLY BLOOM: There are so many uses for spider silk, but let's get back to that most famous-- spider webs. It turns out that being a web spinner could be built into their DNA.

ANTHONY AULETTA: Spiders are born with an innate knowledge on how to construct that shape, which makes sense because most spiders never see their parents. And they never really see other spiders. But the way that they build that is they find an area that has a couple of supports, whether it's twigs or branches or bushes or like the side of a house and a tree.

And it spins a couple of radial lines of silk that go between those two supports. And once they have enough of those, it starts to look like the spokes in a wheel. They go to the center, where all of these crisscrossing radii meet. And they kind of start spinning outwards from there in a spiral shape until they have the completed web.

And as they spin these spirals, that's when they start depositing those little drops of glue. At the same time, they're being very careful to actually not step on those little globs of glue themselves. They have tiny little claws that they grab the web with.

MOLLY BLOOM: Anthony told us it's not the glue that helps them stick to walls.

ROWAN: It's something else.

ANTHONY AULETTA: Not all spiders are capable of sticking to smooth surfaces. But those that can have a patch of really dense little hairs that kind of act a little bit like Velcro against the microscopic texture of the wall.

MOLLY BLOOM: And some spiders use these hairs to help them walk on water.

ANTHONY AULETTA: Many of you may have seen fishing spiders. They're very large brown spiders that live along the coasts of lakes and rivers. And they can actually walk on the water because they have special hairs on their feet that allow them to stay on the surface tension of the water. And some of them get large enough that they can actually catch little fish or tadpoles that swim underneath them.

ROWAN: Is there any spiders that live in the water?

ANTHONY AULETTA: Yes, actually. There is actually one type of spider. You can find it in Europe. It's called the diving bell spider. What a diving bell spider does is it lives in the shallow parts of lakes, where there's a lot of vegetation, lots of plants.

It will dive down into the water and spin a silk dome, supported by these plants. And then it will routinely go up to the surface of the lake and grab a little air bubble, which it holds on its body due to all these tiny little hairs that it has. It'll take the air bubble then, and stick it under the silk dome to keep it trapped there.

And it'll go back and forth and get more and more air bubbles until the whole dome is filled with air. And then the spider lives inside the air bubble so that it can breathe because spiders don't have gills that let them breathe underwater. And while it's there, it'll catch little tiny animals that swim by, mostly little aquatic insects or shrimp-like animals.

MOLLY BLOOM: There's another cool little tidbit of Spider physiology that Anthony shared with us.

ROWAN: Spiders you can deflate.

ANTHONY AULETTA: So when you think about when you move your arms and legs, that's because of muscles. So when you want to extend your arm, you have a certain group of muscles that helps you do that. Spiders don't have muscles like that. Instead, what they do is they change their blood pressure in such a way that when they want to extend a leg. They make the blood pressure really, really, really high in that particular leg, and then just shoot out.

And then when they want to pull that leg back in, they reduce the blood pressure and they have a couple of muscles that help. And this is what caused spiders to have that kind of weird jerky motion that arachnophob, people who are afraid of spiders, really don't like.

Because they move in this way, the pressure inside the spider has to be very, very controlled. Because otherwise, the spider will be moving its legs when it doesn't want to or won't be able to move its legs when it needs to.

And for someone like me, who needs to cut the spider open to see its brain, that's a problem. Because as soon as you make that first cut, the spider deflates like a balloon. And so does the brain.

SPEAKER: Ba ba ba ba ba ba ba ba ba ba ba ba Brains On.

MOLLY BLOOM: We have even more cool spider facts coming your way. But first, we've spun our own little web and set a trap for your ears. It's time for the mystery sound.

SPEAKER: Mystery sound.

MOLLY BLOOM: Here it is--

[MYSTERY SOUND]

MOLLY BLOOM: Any guesses?

ROWAN: A spider that-- that's trying to eat the prey in the hole.

MOLLY BLOOM: Spider trying to eat their prey in the hole. OK. How about you?

DYLAN: Either a spider like tapping on something or moving something over like pushing something over a rocky surface.

MOLLY BLOOM: Both excellent guesses. We will be back with the answer after this.

[MUSIC PLAYING]

MOLLY BLOOM: We want to let you know about a giveaway that we're having. If you head to our Facebook page, you can find a link where you can enter for a chance to win your very own Brains On pocket sized whoopee cushion.

DYLAN: The perfect size for stealthy hiding and noise making at your convenience. The deadline to enter is January 31.

ROWAN: And we'll pick 10 people to win.

MOLLY BLOOM: Head to our Facebook page to find the entry link with more information and the official rules.

DYLAN: You can also email us any time with your questions, mystery sounds, and high fives.

MOLLY BLOOM: Our email address is brainson@m, as in Minnesota, pr.org.

ROWAN: And if you're a fan of Brains On--

DYLAN: Consider leaving a review in iTunes. It really helps other kids and parents find out about the show.

MOLLY BLOOM: And now is the time in every episode, where we honor the curious kids who keep this show going with their ideas, creativity, and high fives. Here's the latest group of kids to be added to the brain's honor roll.

[MUSIC PLAYING]

MOLLY BLOOM: Camila and Diego from Lake Forest, California, Maria from Charlottesville, Virginia, Max from Saint Paul, Elijah from Mountain View, California, Wesley from San Francisco, Milo and Leo from Toronto, Ezra and Nora from Gig Harbor, Washington, Natalie and Ryan from Milwaukee, Zaneira from Johns Creek, Georgia, Maddox and Maverick from Kaneohe, Hawaii.

Amina from Beirut, Eliyahu from New York City, Thomas from Richmond, Virginia, Jacob and Julian from San Diego, Allison from Arlington, Massachusetts, Chelsea from Appleton, Wisconsin, Oliver from San Jose, California, Joshua from Fort Benning, Georgia, Devin from Boulder, Colorado, Kento from Osaka, Japan.

Melanie from Dartmouth, Nova Scotia, Jade from Sydney, Australia, Sadie from Westport, Connecticut, Andrew from Rockford, Illinois, Quinn from North Bergen, New Jersey, Isaiah from Chicago, Corrine from Stanwood, Michigan, Otto from Sarasota, Florida, Claire from Vancouver, Scarlett and Haley from Kensington, California.

Liam, Kaitlyn, Finnegan, and Deirdre from North Olmsted, Ohio, Solomon from Las Vegas, Lucas from Emeryville, California, Saul from Honolulu, Shannin from Dartmouth, Nova Scotia, Tess and Molly from Brooklyn, William and Griffin from Hillsboro, Oregon, Otis from Underberg, South Africa, Ann and Tang from Brisbane, Australia.

[MUSIC PLAYING]

TERRY TARANTULA: Hi. I'm Terry Tarantula. No, no, no, no. Don't run away. I won't hurt you. I know. I know. I'm about the size of your fist. And I'm covered in fur. But seriously, I mean you no harm. Us, spiders, we know our fangs and any may not make for the friendliest appearance.

But think about this. There are 45,000 different spider species in the world. Of those, maybe two dozen have bites that would even make you go to the doctor. So that means of all the spiders, less than one half of 1% could even possibly be harmful to humans.

And I'll let you in on a little secret. We couldn't care less about humans. Don't get me wrong. We love to sink our fangs into a good meal. It's just that, that meal isn't you. In fact, a study found that spider bites are really rare.

It turns out that what people thought were spider bites were actually just rashes or infections or bedbugs or even pimples. Still, no fun. But come on. Don't go blaming the spiders.

SPEAKER: (SINGING) Because spiders are your friends.

DYLAN: You're listening to Brains On from NPR News in Southern California Public Radio. I'm Dylan.

ROWAN: And I'm Rowan.

MOLLY BLOOM: And I'm Molly Bloom.

DYLAN: Entomologist Anthony Auletta really thinks spiders get a bad rep.

MOLLY BLOOM: One thing he wants people to know about is the exciting research going on, inspired by spiders.

DYLAN: There's a scientist building a robot modeled after the cartwheeling spider, which he hopes will be used to explore Mars.

ROWAN: Spider silk is the strongest natural fiber we know.

MOLLY BLOOM: And other scientists are trying to figure out how to produce that silk on a larger scale, and use it for things like lightweight bulletproof clothing.

DYLAN: Biodegradable bottles--

ROWAN: Or bandages.

DYLAN: Or artificial skin or ligaments.

MOLLY BLOOM: Scientists like Maggie Hardy are also researching spider venom.

DYLAN: She's at the University of Queensland in Australia.

MOLLY BLOOM: Remember how spider venom is good at killing insects? Well, she's trying to figure out how we can use spider venom as an environmentally friendly insecticide that kills pests, but doesn't harm humans or pollinators like bees.

DYLAN: And they are finding components in Spider venom that can do just that.

MOLLY BLOOM: It turns out spider venom is pretty complex and layered.

MAGGIE HARDY: Basically, when a spider is eating an insect, it injects the venom. In that venom is something that paralyzes, something that kills it, and then something that starts to liquefy the insides. So if you think of insects kind of like a cup of noodles. Essentially, there's a hard outer shell. And then inside, it's all of their intestines and things like that are just suspended in the broth. So they have an open circulatory system, which means that it's basically just their organs hang in their blood.

So inside that cup of noodles, essentially, the spider just wants to start to mush all that up and, then spider mouths are actually look almost like a brush. And they just suck all that stuff through. They don't end up getting all the bits of exoskeleton and the parts that might injure them. They just get that, essentially, insect milkshake.

ROWAN: How can venom be used in insecticides?

MOLLY BLOOM: The venom peptides, which are small highly structured proteins, are designed to act specifically on different kinds of animals. The ones that can paralyze, say, a moth won't harm a human because we have very different nervous systems.

MAGGIE HARDY: The spider venoms are essentially like a whole bunch of keys. And inside animals, so inside insects or inside humans or inside whatever, you have a specific set of locks. And essentially, what happens in the spider venom if it has that individual peptide, it will match with that one lock. And then it will do something to it. It might open it, it might shut it.

So in humans, we have a specific set of locks that they don't have in insects. And so the individual peptides that act in humans tend to do nothing in insects. So the insecticides that have been discovered, those ones when you test them in mice and rats, so far, they don't do anything.

When we talk about these individual components, what we're really talking about are specific keys for specific locks. And so sometimes, you can look, based on what lock you want to pick.

MOLLY BLOOM: Other people in her lab are researching how different peptides could help humans with chronic pain. But in order to do this research, they need to have venom to work with. Do you guys have any ideas about how they might go about collecting the venom from the spiders?

DYLAN: I think that they probably almost need like only one spider. And then if they are able to like dissect it, and be able to get a tiny bit of the venom, they can run a test on it, and look at the chemicals inside it. And almost copy it and make like bottles and bottles of it.

ROWAN: I think they only make the some kind of like a fake bug, and putting out into the spider's web, and they put it on it, and then it get sucks it in. And then they come by and take it out. And they take the venom, and they take research on it. And then make more of it.

MOLLY BLOOM: Yeah, you guys are both partially right. They are able to make synthetic venom after they are able to analyze it. They do take the venom from living spiders. And they call it milking the spiders.

MAGGIE HARDY: We obviously want to look after them, so that they live for a long time. So we only collect the venom about every fortnight, about every two weeks. Once we have the individual component of the venom we want to look at, we actually just make it in bacteria or yeast.

And it's essentially just like you would do with cows. You can compare what happens at the beginning of a milking and at the end of a milking. And we know that they're actually different compounds in the beginning, the middle, and the end. So they're actually waiting to have the more lethal ones until the end.

And venom, those individual proteins, they're energetically expensive to make. And so the spider doesn't want to just waste them if you're going to go away. It doesn't want to bite you. There's a lot of different components in each venom. And each venom is different from other species.

But also, you can have geographic distribution and variation there. So you can have spiders in one town that have a certain venom profile. And that might be because of the different things that they eat. It might because of their habitat. It might be because of their sex.

So one of the things that I like is that variability, that ability to kind of see something new every time. One of the things I think the most cool is that it's answering some really challenging problems that are really happening in the world.

MOLLY BLOOM: Another challenging problem of the world, the mystery sound. Let's listen to it one more time.

[MYSTERY SOUND]

MOLLY BLOOM: All right. Any new guesses after hearing it again?

DYLAN: Is this like related to a spider? OK. Like dragging something.

MOLLY BLOOM: Dragging something. Sticking to your original guesses?

ROWAN: Yeah.

DYLAN: Maybe even like a trapdoor spider, like springing out of its web. And maybe they're not playing the sound of the spider. Maybe like just when the spider like springs out. They're playing the sound of it's like the top of it of like it's whole like hitting the ground and bouncing a little bit.

MOLLY BLOOM: Oh, I like that idea. Well, here with the answer is zoologist, George Uetz.

GEORGE UETZ: What you just heard is the courtship vibration of a male Schizocosa ocreata which is a very common wolf spider in the Eastern deciduous forest of the United States. The sound is called stridulation. It has a special organ on its pedipalps. Those pedipalps are tiny little legs in front of the mouth.

And there's essentially a file on one segment and a scraper on the other. And when this joint is flexed repeatedly and rotated very, very rapidly, it produces that vibration, which is transferred to the surface of a leaf.

[VIBRATION SOUND]

GEORGE UETZ: This particular spider, our research interest in it is based on the fact that it's communication is multimodal. That is long simultaneous with those vibrations. Spider also has leg tapping and waving displays that are visual. So it communicates in the visual sensory mode and the vibration sensory mode at the same time.

[VIBRATION SOUND]

GEORGE UETZ: There are a lot of animals that use multimodal signaling. And they're all very different. And the question is, why do they do that? One answer is that the message will get through even if one mode doesn't. So if the spider can be seen, but not heard, the female will still know it's a courting male spider rather than a prey item.

And if on the other hand, it can be heard, but not seen, the female will know there's a male nearby even though she can't see him.

[VIBRATION SOUND]

MOLLY BLOOM: Yes. So spiders don't have ears. So they need to communicate a lot through vibrations. So those are some of the vibrations that we just heard.

DYLAN: That's really cool.

MOLLY BLOOM: And now before George Uetz became a biology professor and department chair at the University of Cincinnati, he was a student just like you. When he first went to college, he wanted to study invertebrates as a Marine biologist. But then as luck would have it, he took a class on arthropods that focused on spiders.

GEORGE UETZ: Before I took that course, I really didn't care for spiders at all. I was kind of afraid of them. And when I realized we were spending a lot of time looking at spiders, I was a little unsettled because I was afraid of them.

But when you look at them up close, and you see, you learn very quickly that they're not interested in hurting you. And fear gives way very quickly to fascination.

SPEAKER: (SINGING) Because spiders are your friends.

DYLAN: Spiders spin silk using spinnerets on their bodies.

ROWAN: Silk isn't sticky, though.

MOLLY BLOOM: If a spider makes a sticky web, they actually make droplets of glue to put on it.

DYLAN: Spiders also use silk for transportation.

ROWAN: To protect their eggs.

MOLLY BLOOM: Or to climb or line tunnels.

DYLAN: Spiders are also inspiring lots of cool research.

ROWAN: And even though spider venom may sound scary--

MOLLY BLOOM: It could provide us with safe insecticides and medicines in the future.

ROWAN: That's it for this episode on Brains On.

DYLAN: This episode was produced by Marc Sanchez, Sanden Totten, and Molly Bloom.

MOLLY BLOOM: You can find past episodes at our website, brainson.org, or in your favorite podcast app.

DYLAN: You can follow us on Instagram and Twitter at brains_on.

ROWAN: And we're on Facebook too.

BOTH: Thanks for listening.

SPEAKER: (SINGING) Because spiders are your friend. Spiders are your friend. Spiders are your friends. Spiders are your friends.