10/30/2015

Spider Stories That’ll Stick With You

21:59 minutes

Cannibalism. Bondage. An offering of flesh. Spiders have weird (and wonderful) ways of enticing and entertaining their mates. Catherine Scott, an arachnologist at the University of Toronto, shares some of their more bizarre behaviors, and explains why spiders really aren’t all that scary. And Lauren Esposito, curator of arachnology at the California Academy of Sciences, delves into the origin of arachnids, and why dinner-plate-sized spiders were able to survive in prehistoric times but not today.

  • A pair of black widows (Latrodectus hesperus). Photo by Sean McCann

  • Black widow. Photo by Sean McCann

  • A Pisaura mirabilis with a gift. Photo by Ferran Turmo Gort/flickr/CC BY-NC-SA 2.0

  • Agelenopsis aperta mating. Photo by Sean McCann

  • Fishing spider (Dolomedes triton). Photo by Sean McCann

  • Pirate spiders (Mimetid vs. cyclosa). Photo by Sean McCann

  • One of Catherine Scott’s “pet” spider collections. Photo by Sean McCann

Segment Guests

Catherine Scott

Catherine Scott is an arachnologist and PhD student at the University of Toronto in Toronto, Canada.

Lauren Esposito

Lauren Esposito is Curator of Arachnology at the California Academy of Sciences in San Francisco, California.

Segment Transcript

[MUSIC PLAYING] IRA FLATOW: When you encounter the first spooky spider this Halloween evening, I’m hoping you will have a better appreciation for the eight-legged among us, because no matter what spider scare someone has for you, it can’t compete with the real thing. Let’s take the spider’s web first.

Not all spiders advertise their traps. Some of the cowboys of the arachnid world, they actually wait for moths to fly by and sling a sticky yo-yo at them, catching their prey midair. Others actually fish for their prey.

Yeah. Some spiders do go underwater. It’s a weird world out there, once you get to know the ways of spiders. A world of cannibalism. We’ve got bondage. You have gifted corpses and narcotics.

And my next guest has a few tales to spin, so to speak. So next time you see a spider, you won’t be spooked. You might be bewitched instead.

Catherine Scott is an arachnologist and a PhD student at the University of Toronto in Canada. Welcome to Science Friday.

CATHERINE SCOTT: Hi there.

IRA FLATOW: Let’s start first. A good place to start, one of the strangest spider mating stories. The Australian redback spider.

CATHERINE SCOTT: Yes. Redbacks are really cool spiders, and have some interesting mating behavior. In the redback spider, males actually actively sacrifice themselves during copulation.

So you might have heard of black widows and the idea that the female eats her mate. Redback spiders are a species in the genus Latrodectus– the genus of black widow spiders. And like I said, in this species, the male, as he’s transferring sperm, will perform a somersault and offer his abdomen to the female. And she can start snacking on his abdomen as they are mating.

IRA FLATOW: Does she eat everything in the abdomen?

CATHERINE SCOTT: So she does end up killing and completely consuming the spider. But the males of the species have a really great adaptation. So one of the neat things about spiders is that they have paired copulatory organs. And the female has correspondingly paired openings to her reproductive tract.

So he has to mate twice in order to fully inseminate the female. So as he’s transferring sperm with his first copulatory organ, the female starts chewing on his abdomen. But he’s able to constrict his abdomen in such a way that he sort of compartmentalizes his body so that the female is eating the tip of his abdomen, but the rest of his body is still functional, so he can stay alive and survive to do his second copulation. And then once that’s done, the female will kind of give him a hug, gather him in, and start feasting away.

IRA FLATOW: I’m sure there’s a movie here somewhere.

CATHERINE SCOTT: Yeah.

IRA FLATOW: About that. One of my favorite stories– one of the most enduring spider mating behaviors– is the presentation of a gift.

CATHERINE SCOTT: Yes. Yes. Some spiders are sort of romantic like that. In two different closely related families called the pisauridae and the [INAUDIBLE], so these are fishing spiders and long-legged fishing spiders.

The male of these species will present a gift to the female before mating. And so he takes a nice, juicy prey item and wraps it up in silk and then presents it to the female. And she’ll accept the gift.

And as she’s feeding on it, the male will copulate. And it turns out that males who provide a gift to the female are able to copulate longer and transfer more sperm than males that don’t offer a gift. However, both males and females can sort of cheat at this game. So sometimes the female– if the male doesn’t wrap the gift in this beautiful silk gift wrapping, the female might accept the gift but then run off with it and not mate with him.

So if he does wrap it with silk, that helps him to maintain a grip on it, so that even if she does try to abscond, he’ll just hang onto it and get dragged along with her. And then once she settles down to eat, he’ll sort of spring back to life and try to mate with her again.

But the males also, sometimes what they’ll do is they’ll wrap up a worthless item in silk and try to disguise it. So they’ll take a seed or a prey carcass that they’ve already fed on, and wrap that with silk and present it to the female. And because it’s covered with silk, she’ll accept it initially. And the male will start to mate. But then once she realizes that there’s nothing to eat inside, she’ll quickly cut short the copulation. So that’s not so great for the male.

IRA FLATOW: So many metaphors I could go with that I’m not going to go. I’m sure you’ve thought about them yourselves at one point or another.

I’d like to bring out another arachnologist who, yes, has milked scorpions for their venom. Just another day at the office, right, Lauren? Lauren Esposito is curator of arachnology at the California Academy of Sciences in San Francisco. Welcome to Science Friday.

LAUREN ESPOSITO: Thank you.

IRA FLATOW: How often do you do milk scorpions for their venom?

LAUREN ESPOSITO: Well, you know, it’s not my average day at the office. But it’s something that I do fairly regularly.

IRA FLATOW: Well, tell us about the history of arachnids. How far back do they go? Are they all that ancient compared to other invertebrates?

LAUREN ESPOSITO: Absolutely. So arachnids are one of the oldest terrestrial arthropod groups. And so what that means is before insects or any other hinge-legged animal walked the planet, at least above the surface of the water, there was arachnids.

And so most of the arachnid groups date back to at least 400 million years. And so that’s long before the dinosaurs, long before flowering plants. And so they’re really an ancient group.

IRA FLATOW: OK. And the scorpions are the oldest?

LAUREN ESPOSITO: Scorpions are probably the oldest. So with scorpions, we’re looking at about 430 million years. And these were really monster scorpions. They’re not like the tiny little cute scorpions of today.

They were really monsters. And before they came out on land, they ruled the seas. They’re the ancestor of scorpions was a creature called the Eurypterid. And the Eurypterid, they’re often referred to as sea scorpions, because they look quite similar to scorpions. They have sort of a long whip in place of the scorpion tail.

And they were the kings of the sea. They ate all the other things that were living in the ocean at the time, and then eventually came up onto land as sort of amphibious animals. And what we think they were doing was they were coming up along the shores of rivers and morphed into this semi-aquatic lifestyle where they could come up on land and fish.

And so they were probably eating things like salmon.

IRA FLATOW: Wow.

LAUREN ESPOSITO: And so you can imagine these like two-meter long beasts coming up on the shore to grab salmon. So they were essentially doing what grizzly bears do today.

IRA FLATOW: Wow. We’re talking about the spider this hour in Science Friday from PRI, Public Radio International. Talking with Catherine Scott and Lauren Esposito.

Now Catherine, I know one of your missions is to convince people that spiders aren’t scary. They’re not evil. They’re not out to get you.

And you walk the walk. I actually saw a picture of you letting a black widow crawl on you sometime.

LAUREN ESPOSITO: Yes. Yeah. I have handled black widows. They’re actually very shy, unaggressive spiders that really don’t deserve their poor reputation. And yeah. I do a lot of outreach trying to convince people that spiders really have no interest in biting people.

Some spiders can hurt people. They’re medically significant. In North America there’s only two kinds of spiders that can really hurt people. And that’s the widow spiders– and there are a few species of those, and then the brown recluse spider.

IRA FLATOW: So what should you do if a spider– possibly venomous, scorpion, whatever, black widow is crawling on you? Just leave it alone?

LAUREN ESPOSITO: Yeah. So I mean, if they happen to be crawling on you, the best thing to do would be to just sort of let them continue. And if they just crawl off, then that’s great. Or you can sort of try to– the way that I get black widows to move around is by gently brushing their hind legs with a soft paintbrush.

And so if you’re sort of tickling from the behind, they’ll walk forward. And then you might be able to convince them to walk off of you.

But the chances of having a spider on you are pretty low. Contrary to popular belief, spiders do not go into your bed at night to bite you, or try to go into your mouth. That myth that you swallow spiders is totally false.

IRA FLATOW: Unless you’re Sean Connery in Dr. No, you don’t. You know what I’m talking about.

LAUREN ESPOSITO: Yeah. But yeah. So my main message is that spiders really have no interest in biting people, unlike a lot of other arthropods like mosquitoes, and ticks, and mites that feed on human blood. That’s part of their lifestyle. That’s what they do.

Spiders do not feed on humans. They bite insects and other spiders, not humans. So really the only reason a spider would crush you– or would bite you is if you’re crushing it, or sort of otherwise harassing it, and it feels like it’s got no other choice but to try to defend itself.

IRA FLATOW: We asked our fans on Twitter for a few things that scare them, in hopes that you can reassure them. Maybe we’ll get to some of them before the break.

The legs and the sudden movements, said Eva [INAUDIBLE].

That was really a common complaint. Too many legs. You know. Not much we can do about that.

LAUREN ESPOSITO: And even a lot of entomologists say that that extra two legs, that’s just two too many. And people who study insects for a living find spiders creepy, just because of that number of legs.

And the way that they move is also disconcerting sometimes. Yeah.

IRA FLATOW: Yeah. Liza R. says that what really scares her is their ability to disappear. If you see one on the wall, you squish it with a tissue, you look at the tissue, spider is not in it, nor on the wall.

LAUREN ESPOSITO: I’m not sure what to say about that one. Probably it was a small spider. But they can move pretty fast.

CATHERINE SCOTT: The same things happens with mosquitoes.

IRA FLATOW: Yeah. You know. You just gotta give them a little more pressure.

We’re going to take a break and come back and collapse more. Maybe we’ll talk about the scorpion and your fears with Lauren Esposito, curator of arachnology at California Academy of Sciences in San Francisco, and Catherine Scott, arachnologist and Ph.D. Student at the University of Toronto in Canada.

Our number is 844-724-8255. You can also tweet us @scifri.

This is Science Friday. I’m Ira Flatow, we’re talking spiders this hour, their unusual, sometimes creepy behaviors, and why you really shouldn’t be afraid of them. And whenever I see a spider in my house, I know it’s there for a good reason. I don’t want to kill it. So It’s doing good stuff.

I have two arachnologists on with me today. Catherine Scott, a PhD student at the University of Toronto in Canada. Lauren Esposito, curator of arachnology at the California Academy of Sciences in San Francisco.

Lauren, I know that one of the things you’re most interested in is venom. And spiders and scorpions are practically pharmacies. You can have hundreds of different drugs from each one.

LAUREN ESPOSITO: Exactly. So they’re sort of venerable pharmacies, so to speak. A given individual spider or scorpion might have 200 unique types of venom that it makes in its sort of venom arsenal. And the really cool thing about those venoms is they’re all really specific for particular organisms and particular parts of those organisms.

IRA FLATOW: So could we like farm them when looking for new drugs for people?

LAUREN ESPOSITO: Yeah. And indeed, people are farming them. So there’s all kinds of venom components that are currently being researched for their therapeutic properties. Everything from treating erectile dysfunction to treating drug-resistant bacteria.

IRA FLATOW: Tell me about the drug-resistant bacteria.

LAUREN ESPOSITO: Right. So there was an interesting study that was released about a year ago. And what they did was they took mice, and they infected those mice with MRSA, which is a resistant species of bacteria that’s very common in hospitals, and poses a really huge problem because it’s resistant to traditional antibiotics.

And so what they did was they infected these mice with this bacteria. And then they treated the mice with either a placebo, no treatments, or they treated it with this venom, peptide. And they found that in the mice that were infected that were then treated with the venom peptide, they were completely cured of MRSA in four days.

IRA FLATOW: Wow. Four days.

LAUREN ESPOSITO: Yeah. Four days. Astounding.

IRA FLATOW: So where is that drug now?

LAUREN ESPOSITO: Well, you know, these things take time. And so that was the first of I’m sure many studies that have to be done before it can be fully approved by the FDA. But it’s promising research. And it’s pointing us in the right direction.

And there’s similar research being done to treat things like chlamydia and certain other bacterial infections. But there’s also more interesting– perhaps not important– but more interesting therapies for treating things like muscular dystrophy and Alzheimer’s.

IRA FLATOW: Wow. But you know where all the money is in these days. It’s in that little blue pill for erectile dysfunction.

LAUREN ESPOSITO: Right. Indeed.

IRA FLATOW: So here there’s something with spiders about that?

LAUREN ESPOSITO: Right. So most scorpions and many spiders have an effect called priapism after they bite you. And so because there’s not many spiders that affect humans specifically, that doesn’t happen very often. And what priapism means is an erection. It causes blood to fill the cavities of the penis and cause an erection.

And so what happens is it’s very painful. And you have to take an anti-venin. And that anti-venin will counteract the effects of the venom. But what is interesting is that it happens. And it’s something that’s on the minds of many, particularly all those that are investing monthly in their supply of little blue pills.

And so what people are researching is how to harness this property of venom peptides and use it for a drug that has little to no side effects.

IRA FLATOW: Interesting. Catherine, let’s talk about another spider trick. Pheromones. Some of them can be almost like narcotics, right? They can knock a spider out?

LAUREN ESPOSITO: Yeah. So that’s the story about a spider called Agelenopsis agrata. It’s a funnel-weaving spider, very similar to house spiders that are in a lot of homes in North America. In the same family.

And in this spider, males produce a pheromone that they waft over the female with their pedipalps in front of their face. And it causes the female to enter a passive trance-like state. So to us it looks almost as if she’s been knocked out. It’s not clear whether it’s sort of her decision to become passive, or whether this male pheromone is causing her to enter that trance.

But once she does, the male is able to sort of haul her around the web, position her the way he wants, and then mate with her.

IRA FLATOW: Wow. We don’t think of these spider’s having these kinds of powers. You know. What we think about is they have a web. They spin a web and they catch things in it.

LAUREN ESPOSITO: Yeah. The really cool thing about spider webs is that they’re not just for prey capture. Female spider webs actually also function like personal ads. Web-based personal ads.

So the female has pheromones on her silk that’s sending a message to males from a distance, and providing him with information about her location, her sex, whether or not she’s mated, whether or not she’s hungry, which can be really important for males, because courting a big female can be risky because some spiders are cannibalistic. So yeah. They have these really sophisticated scent-based communication systems.

IRA FLATOW: Let’s go to the phones to Craig in Tallahassee. Hi, Craig. Welcome to Science Friday.

CRAIG: Good afternoon, Ira, Dr. Scott, and Esposito. I recently saw on the internet, of course, a video of somebody’s pet tarantula molting its skin. And very, very freaky. You were asking what scares you. That was one of those. It just touched me primally inside how odd this thing looked.

I was wondering if all spiders molted. It was very interesting. It came out fully formed with hair and fangs. And the owner said it was still very soft and took hours to harden. But do all spiders shed their skin in order to grow?

IRA FLATOW: Wow. Great question. Thanks for calling. Catherine?

CATHERINE SCOTT: Do you want to answer that, Lauren?

LAUREN ESPOSITO: Yeah, sure. So indeed, all arthropods molt. It’s really interesting in spiders, because when they molt, what they’re actually doing is growing. So their skeleton is rather than being in the middle of all their muscles, it’s surrounding all of their muscles and containing them, acting sort of as an armor.

But in order to grow, they have to get rid of it so that they can grow a bigger one. And so what they do is they actually shed their entire skin. And not just their skin, this is also their armor, their skeleton. They can’t move until it’s rehardened.

But on top of that, they’re shedding their entire digestive system and their respiratory organs. And so during that molting process, the spider is getting a whole new suit, so to speak. And then until they’ve rehardened– it can take several hours– they’re really vulnerable. And so they don’t want to do it very often. And when they do shed, they need to be in a safe spot. Otherwise, they’re going to get eaten.

IRA FLATOW: Sounds like a soft-shelled crab sort of thing.

LAUREN ESPOSITO: Just like that.

IRA FLATOW: So one question to you, Lauren. Back in prehistoric times– that’s way back– we had giant ferns, giant dinosaurs, and so on. Were there also giant spiders back then?

LAUREN ESPOSITO: There were. There were indeed giant spiders. And so some of the spiders were half a meter in size. They were really, really big.

IRA FLATOW: Half? Let me walk that back a second. Half a meter in size?

LAUREN ESPOSITO: Half a meter. Yeah. Half a meter. Half a meter spiders. But you have to think, the dragonflies were also a meter big.

IRA FLATOW: So lunch was bigger. So how did they grow so big back then? What allowed them to grow so big?

LAUREN ESPOSITO: That’s a really great question. So the answer is oxygen. And so because– spiders, and insects as well, typically have passive respiratory systems, which means the way they breathe is they just allow air to pass over their lungs, would are called book lungs.

And so they can’t breathe in and out like our lungs are. So when they start running too quickly, they have to stop and let the oxygen pass over. They can’t breathe harder. And back then, there was a lot more oxygen in the air. And so because the oxygen concentrations were greater, they were able to grow larger because enough oxygen could get to all of their cells.

IRA FLATOW: Wow. Let me ask one last question. What’s the thing you want most people to know about spiders, that you love, but we don’t know.

LAUREN ESPOSITO: You know. I’m going to talk about arachnids generally, and not just spiders. Because I do love all arachnids. I study scorpions and [INAUDIBLE]. And what I’d like to share is that they’re cuddly. That’s my message. Spiders and scorpions and other arachnids are cuddly creatures.

And my evidence for that is that they take care of their young. So scorpions, for example, give birth to live young. The females become pregnant. And when they give birth, the babies come out as small baby scorpions. And the mother will take them up on her back, and she’ll take care of them until they get big enough to fend for themselves.

IRA FLATOW: Cute. Very cute. Catherine, do you have something we should all know?

CATHERINE SCOTT: Yeah. So that’s a great thing about arachnids that I love as well. I think, yeah, my main message is that spiders don’t deserve their bad reputation, that they have no interest in biting you. bites are extremely rare.

And yeah. I think spiders are a lot more fascinating than scary. And if you learn more about them, start watching their behavior. Their behavior is really cool. And they’re beautiful. And so, yeah.

IRA FLATOW: Well you got us talking about it today. You certainly got us started thinking about that it today.

I want to thank both of you. Catherine Scott, a PhD student at the University of Toronto in Canada.

Lauren Esposito. Curator of a arachnology at California Academy– Cal Academy, as they say– of Sciences in San Francisco. Thank you both. And Happy Halloween to you.

CATHERINE SCOTT: Thanks so much.

LAUREN ESPOSITO: Happy Halloween. Thanks for having us.

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