In short
Radiolab Episode Notes: Snail Sex Tape
Episode Overview In the "Snail Sex Tape" episode of Radiolab, hosted by Molly Webster, the focus is on the fascinating and often overlooked sex lives of snails. The episode features evolutionary biologist Menno Schilthuizen as a guide who explores the intricacies of snail reproduction, including unique mating behaviors, anatomy, and evolutionary significance.
Key Themes
- Snail Anatomy and Mating: The episode dives deep into the anatomy of snails, particularly their reproductive organs and mating practices.
- Evolutionary Biology: It discusses how snails serve as fascinating subjects for studying evolution due to their slow movement and distinctive reproductive strategies.
- Unusual Mating Behaviors: Highlights the concept of "love darts," which are used by snails during copulation.
Detailed Summary
Introduction to Snails
- Molly and Soren's Exploration: The episode begins with Molly Webster and Soren Wheeler discussing their contrasting environments while searching for snails—Molly in Brooklyn and Soren in Borneo.
- Snails as Study Subjects: Menno Schilthuizen emphasizes snails' accessibility for studying evolution due to their stationary nature.
Sexual Anatomy of Snails
- Hermaphroditism: Snails possess both male and female reproductive organs, leading to unique mating rituals.
- Mating Process: The mating process typically involves face-to-face positioning, and each snail extends its penis toward the other.
Love Darts
- Definition and Function: The episode introduces the concept of love darts—small, sharp structures that snails shoot at one another during mating to enhance reproductive success.
- Production of Love Darts: Love darts are produced in the dart sack and can either stay in the partner or be expelled after mating.
- Hormonal Influence: Menno explains that love darts deliver hormones into the recipient snail's bloodstream, promoting sperm uptake and influencing reproductive success.
Evolutionary Insights
- Dual Nature of Reproductive Strategies: The episode discusses the "arms race" between male and female snails, highlighting how evolution drives competing reproductive adaptations.
- Variety of Dart Types: Different snail species exhibit varying dart shapes, sizes, and mating strategies, showcasing the diversity of evolutionary adaptations.
Cultural Reflections
- Medieval Marginalia: Menno mentions historical illustrations depicting snails with swords, hinting at the cultural imagination surrounding snail reproduction.
- Relation to Myths: There's speculation that historical encounters with love darts may have inspired myths, including those surrounding Cupid.
Conclusion
- Call to Action: Molly encourages listeners to explore their local environments to find love darts and witness snail mating behaviors, fostering a connection to the natural world.
- Resources: The episode concludes with mentions of Menno Schilthuizen's book, "Nature’s Nether Regions," which further explores the subject of snail reproduction.
Episode Credits
- Hosted by: Molly Webster
- Reported by: Molly Webster
- Produced by: Mona Madgavkar, Annie McEwen, Molly Webster
- Sound Design: Mona Madgavkar, Annie McEwen
- Fact-Checking: Diane A. Kelly
- Edited by: Alex Neason
Episode Citations
- Various academic articles and videos are referenced in the notes, providing additional resources for listeners interested in further exploration of the themes discussed in the episode.
Listening and Engagement
- Listeners are encouraged to engage with the podcast through social media and newsletters, ensuring they remain connected to ongoing discussions and discoveries in science.
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This markdown summary serves as a comprehensive guide to the episode, highlighting its main themes, key discussions, and the intriguing nature of snail reproduction, while also offering pathways for further exploration.
Written by AI. May contain mistakes. Listen to the episode to check what was said.
Chapters
Tap a time to open that second in VOA Walk to Discover Snails
1:30 to 3:16
Join the hosts on a journey to explore snails and their unique biology.
“And today I am joined by our executive editor, Soren Wheeler.”
The Fascinating World of Snail Evolution
3:16 to 5:15
Understanding how snails evolve and their unique patterns.
“So it turns out that penis in the face is actually like maybe one of the least strange things about snails.”
Comparing Snails and Slugs
5:15 to 7:03
Explore the relationship between snails and slugs and their anatomy.
“is that you can see evolutionary patterns on a human scale, which normally you would need entire continents for.”
Snail Anatomy and Mating Rituals
7:03 to 9:21
Delve into the unique mating rituals and anatomy of snails.
“Actually, many slugs haven't completely lost their shell.”
The Complexity of Snail Reproduction
9:21 to 12:15
Learn about the intricate reproduction methods of snails.
“And the penis of the one partner pushes into the vagina of the other partner and simultaneously vice versa.”
The Duel of Snail Mating
12:15 to 13:23
Understanding the competitive nature of snail mating.
“They could do that or they can like store.”
Understanding Love Darts in Snails
17:16 to 19:11
Explore the fascinating role of love darts in snail reproduction.
“want to better their odds for that sperm to become babies and so at this moment they bring out They're love darts.”
Hormonal Manipulation in Snail Mating
19:11 to 22:04
Learn about the hormones involved in snail mating and their effects.
“My gosh, I've never actually had snails, but now I...”
Dart Mechanics and Mating Rituals
22:04 to 24:30
Discover the intricacies of how snails use love darts during mating.
“You're saying that when this hormone hits the system of the partner, what you could call the vagina, and it like makes it seize or like cramp or something?”
The Evolution of Reproductive Organs
24:30 to 27:28
Understand the evolutionary arms race in snail reproduction and love darts.
“Yeah, they leave those darts on the floor.”
Show all 13 chapters
The Magic of Love Darts
27:28 to 28:00
Experience the wonder and unexpected complexity of snail reproduction.
“I mean, I, evolution aside, I'm just sort of, I had no, like I thought snails, maybe they just slime up next to each other and then there's a sack of eggs or something.”
Exploring the Magical World of Love Darts
28:00 to 29:48
Discover the enchanting world of love darts and their historical context.
“It's almost like it's almost like being it's so funny to say this to a scientist.”
Finding Love Darts in Brooklyn
29:48 to 31:05
Learn how to find love darts and observe snails in their natural habitat.
“Well, they're in Prospect Park in Brooklyn on trees.”
Transcript
Automatic transcript. May contain errors.0:00Aaron Chase:WNYC Studios is supported by the New Museum, bringing contemporary art from around the world to lower Manhattan. The New Museum opens its expanded building on the Bowery on March 21st with New Humans, Memories of the Future, an exhibition spanning the entire museum and featuring 200-plus local and international artists. Details of our opening weekend, ticket registration, and membership information are available at newmuseum.org.
0:26Molly Webster:Radio Lab is brought to you by Progressive Insurance. You chose to hit play on this podcast today? Smart choice. Make another smart choice with AutoQuote Explorer to compare rates from multiple car insurance companies all at once. Try it at Progressive.com. Progressive Casualty Insurance Company and Affiliates, not available in all states or situations. Prices vary based on how you buy.
0:53Molly Webster:Wait, you're listening. Okay. All right. Okay. All right. You're listening to Radiolab. From WNYC. See? Yeah.
1:10Aaron Chase:Am I recording? I'm recording.
1:13Molly Webster:Does your mic have fancy green lights on it?
1:16Aaron Chase:Does yours not?
1:17Molly Webster:No.
1:17Aaron Chase:It tells me how loud it is. And I can also mute it. Can you hear me? You can't hear me anymore.
1:22Molly Webster:No, I can still.
1:24Aaron Chase:Oh, you can't?
1:24Molly Webster:Yeah.
1:25Aaron Chase:Wait, what does that button mean then?
1:27Molly Webster:Button. Button.
1:29Aaron Chase:I'm Molly Webster. This is Radiolab. And today I am joined by our executive editor, Soren Wheeler.
1:37Molly Webster:What are we doing?
1:38Aaron Chase:Why are you here? Well, you're here because I'm going to take you on a walk.
1:42Molly Webster:Oh, you're going to take me on a walk?
1:44Menno Schilthuizen:Where? In a lowland area along the Kinabatangan River.
1:47Aaron Chase:We're going to follow this guy, Menno.
1:49Menno Schilthuizen:Menno Schildhuizen. He's an evolutionary biologist. Seems like a nice guy to go on a walk with.
1:54Aaron Chase:Menno is going to take us deep into Borneo.
1:56Menno Schilthuizen:It's tropical, humid limestone forest, so it's really wet.
2:01Aaron Chase:There's lichens, there's ferns.
2:03Menno Schilthuizen:Orchids and vines and climbers.
2:06Aaron Chase:And he is looking for something.
2:09Menno Schilthuizen:Okay.
2:09Aaron Chase:And actually, I also went on a walk to look for the something. My walk was not in Borneo, it was in Brooklyn in February. So less orchid, dog poop, more cigarettes, trash. Here's a pigeon.
2:23Molly Webster:So this is something that you can find in both Borneo and Brooklyn.
2:28Aaron Chase:Yes. In Borneo, it's down by the riverbanks.
2:30Menno Schilthuizen:And the limestone cliffs.
2:32Aaron Chase:In Brooklyn. Oh, no, I'm right here. You just make your way through one single door to a store. And then right there, there is a glass tank. I'm pressing my face up against the glass.
2:44Menno Schilthuizen:Really put my face to the surface of the rock. And then glistening in the sun. Oh, my goodness. I see these miniature. Tiny, tiny. Snails.
2:58Molly Webster:Snails? Mm-hmm.
2:59Aaron Chase:It's got a little brown shell with whorls.
3:02Molly Webster:Is the thing that we went on a walk to see. Right.
3:04Aaron Chase:It's got two little antennas. And I just can't imagine a penis coming out of that face.
3:13Molly Webster:Oh. Wait, what?
3:19Molly Webster:There's a penis in the snail's face?
3:21Aaron Chase:Wait. So it turns out that penis in the face is actually like maybe one of the least strange things about snails. Soren, you look at snails and you think like...
3:35Molly Webster:I don't think anything. I haven't ever thought. Okay, fine.
Read the full transcript
3:37Aaron Chase:You don't even think about snails. And I'm here to tell you that there is so much to see when you look at a snail, including a sex life that I don't think any of us saw coming. And so that's what we're going to do today. we're gonna do snails or they're gonna do each other and we're just gonna watch in i'm in okay and oh dear our guy meno is gonna be our guide exactly so let's go okay um
4:08Menno Schilthuizen:well to begin with i wasn't originally interested in snails i mean as a school boy i was i was mostly interested in insects and birds but you can study things in snails that you cannot study in insects. And that often has to do with the fact that they move so slowly. So you can see.
4:27Aaron Chase:You can catch them.
4:28Menno Schilthuizen:You can catch them. You can mark them. So I've put numbers on snail shells and found them back a year later or sometimes two years later sitting on the same tree that they were sitting on when I marked them. No way. That's cute. You know, people do that with insects too. But the chance of finding them back is much smaller than with snails who mostly sit where you left them. So they call this the rate of dispersal. So that's basically the average distance between where an animal is born and the place where it has its first reproduction.
5:01Aaron Chase:Okay.
5:01Menno Schilthuizen:And in snails, that's usually between one and five meters. Oh, really?
5:06Aaron Chase:So that's not very far at all.
5:08Menno Schilthuizen:It's not very far at all. And that's the consequence of that is that you, and that's really what got me hooked on snails, is that you can see evolutionary patterns on a human scale, which normally you would need entire continents for. So in Crete, where I did my PhD, I would walk through the mountains and with every step I would see subtle changes in the way the snail shells looked. So if you cover a few kilometers, you can see snail shells around you sitting on the rocks changing from smooth to ribbed and from large to small. So you basically can walk through evolution.
5:45Aaron Chase:So when he's taking this walk, there's like a giant cliff of rock. And in one tiny patch, there are a species of tiny snail. And one day, some of those individuals wander over to a very nearby patch of rock. And then they settle there and evolution acts on them. And then some of them leave and go to another nearby patch of rock. And so basically you can walk patch to patch to patch and see how evolution has shaped these snails.
6:16Molly Webster:Well, I'm fascinated by the idea that you can walk along this, but I'm like, yeah, what do you see when you go? A slightly different shell or a different antenna? Slimier or less slimier?
6:26Menno Schilthuizen:Oh, you're looking at the size, whether it's a flat shell or a tall spire-shaped shell, whether it has any ribs. but sometimes the shells between different species are very similar. They're just smooth and spirally, and you can't really tell one species from the other very easily. And you have to start to dissect. And with slugs, of course, you don't even have a shell, so there you always have to dissect.
6:53Aaron Chase:Wait, so snails and slugs are as closely related as they look?
6:56Menno Schilthuizen:Yeah, slugs have evolved from snails, but during that process they've lost their shell. Actually, many slugs haven't completely lost their shell. So usually you need to dissect them to really be sure what you're dealing with. And then you start meeting all this complex, this whole complex genital world of snails. Straight to the genitals?
7:20Aaron Chase:Yes.
7:21Menno Schilthuizen:I should have known given that you were...
7:22Aaron Chase:I was like, snails have genitals? Yeah.
7:25Menno Schilthuizen:When you have species that are very closely related and very similar on the outside, usually their reproductive organs, their genitals are wildly different. So genitalia are the organs that evolve the fastest among all organs in an animal's body. And the result is that anything that is possible in evolution is going on in genitalia. It's really where the rubber hits the road.
7:52Aaron Chase:So just to set the scene here, the snails that Menno is talking about are hermaphrodites, which means that they are both male and female at the same time. So they have both male and female parts inside their little slimy snail body.
8:09Menno Schilthuizen:So snails are very asymmetric in the way their bodies are shaped. And the result of that is that snails usually have their genital opening on their right hand cheek. So you have these eye tentacles and a little bit behind the right eye tentacle, there's a little opening, very hard to see. and that's the place where both the penis and the vagina sit. I like it.
8:32Aaron Chase:It's on their right-hand cheek, not even their butt cheek, just on their face.
8:35Menno Schilthuizen:On their, just, yeah. So when they mate, they have to bring these openings together. So usually they mate face-to-face or actually cheek-to-cheek. Dancing cheek-to-cheek. Exactly. Then they have to get these two openings together and then both of these animals evert their penises which are inside their bodies, but they basically evert like a finger of a glove.
9:03Aaron Chase:So like if you have a glove or something and you pull your hand out and the finger goes inside the glove, that's how it is tucked in. And then when the snail gets to another snail it wants to mate with, it puffs that finger back out again.
9:17Menno Schilthuizen:Yeah, well, that's then true for the penis. The vagina stays where it is. And the penis of the one partner pushes into the vagina of the other partner and simultaneously vice versa. So when you see them mating, you see basically two fingers connecting them through that little opening. Okay. That's the first step. But it does take several hours usually. Really?
9:43Aaron Chase:Hours? Yeah.
9:45Menno Schilthuizen:Many snails mate for, you know, two, three, four, five, up to seven hours. I've seen snails mating for an entire night. They usually mate during the night, so it can take the whole night for them to get all this process underway.
10:00Aaron Chase:It reminds me of some sort of like dial-up internet. Yeah, yes, exactly. You're like, okay, we're connected. Now we're waiting to connect.
10:10Menno Schilthuizen:Almost as long as setting up this interview took. Yeah. Oh my gosh.
10:16Aaron Chase:And they are just connected by these fingers the whole time.
10:20Menno Schilthuizen:Yes. Again, it depends on the species. This is really where the evolution of genitalia kicks in. There are these fingers. There are also sort of tongue-like structures. There's one family of slugs that has these with which they lick each other, and these tongues are attached to the penis. There are also species that don't insert their penises into the partner, but they keep the penises dangling on the outside, and the sperm is transferred by a sort of handshake from one penis tip to the other penis tip. There's a species of tiger slug from Southern Europe where this happens at the end of a penis that is almost a meter long.
11:00Menno Schilthuizen:What? So that would be like 25 inches, more even, I think.
11:05Aaron Chase:That's two feet.
11:06Menno Schilthuizen:No more, 35 inches. Yeah, it's three feet. It's about three feet. And these are actually contenders for the longest penises compared to body lengths in the animal world.
11:17Aaron Chase:Well, yeah, it seems like it would just tip over a slug.
11:20Menno Schilthuizen:Yeah, well, it's like spaghetti. I mean, like cooked spaghetti. It's very flexible. So they hang from a tree and these penises dangle down and they entwine. And at the tip of the penis, the sperm package is transferred. Oh. So the sperm package is quite large and quite nutritious, and it has millions of sperm in it, sperm cells. And they don't produce it beforehand. They produce it while they're mating. So they have to wait for that sperm package to be ready and filled with sperm. And that travels then through the penis into the sperm-receiving organ of the partner. And again, this happens in both directions simultaneously.
12:00Menno Schilthuizen:But it's only like one out of a thousand sperm gets to go to where the eggs are. The rest is being digested, is being eaten.
12:11Molly Webster:Oh, they can eat the sperm.
12:12Aaron Chase:Yes, they can actually just kind of absorb it and like use it to live off of, use it as a food source. They could do that or they can like store. They have a way to store sperm.
12:25Molly Webster:If they're just not now is not the right time for me to I'm working on my snail career. and I don't really want to get pregnant.
12:31Aaron Chase:Up and coming after. It's funny, but like if you are a snail who spent the better part of seven hours getting ready to swap sperm, you don't want it to be eaten, you know? And so to prevent that from happening, the sex game becomes less of a partnership dance and more of a duel.
12:59A duel.
13:00Menno Schilthuizen:Which involves all these weird organs that they use in their reproduction, like sperm storage organs and sperm digesting organs and darts glands and darts sex. And it's a whole circus of sexual extravagance.
13:20Aaron Chase:That is coming up after the break.
13:24Molly Webster:Okay.
13:34Molly Webster:Hey, Lulu here, and this episode is sponsored by BetterHelp. It is March, in like a lion, out like a lamb, and somewhere in the middle, it's International Women's Day. And BetterHelp wants us all to just take a moment to consider the women in our lives, our personal lives, our society, and thank them for their strength and for all that they carry. That work matters. They matter. You matter. And therapy offers a space for all of us to take care of ourselves in the way we deserve. Think about the roles you play for the people you love. Think about how those roles, intentionally or not, weigh on you, and in the worst moments, work to weigh you down.
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16:17Molly Webster:That's O-D-O-O dot com. This is Ira Flato, host of Science Friday. For over 30 years, the Science Friday team has been reporting high-quality science and technology news, making science fun for curious people by covering everything from the outer reaches of space to the rapidly changing world of AI to the tiniest microbes in our bodies. Audiences trust our show because they know we're driven by a mission to inform and serve listeners first and foremost with important news they won't get anywhere else. And our sponsors benefit from that halo effect. For more information on becoming a sponsor, visit sponsorship.wnyc.org.
17:07Molly Webster:hey hey i'm molly you're soren yes and i think we are about to have a duel i promised a duel
17:15Aaron Chase:and a duel you shall get which is like there are two snails they are about to swap sperm but they want to better their odds for that sperm to become babies and so at this moment they bring out They're love darts.
17:30Menno Schilthuizen:Love darts? Love darts, they're produced in an organ called the dart sack. And the dart is a little limestone needle made from the same material as the shell. Shaped like a little dagger. Oh, really?
17:48Aaron Chase:Yeah.
17:49Molly Webster:Can I Google it?
17:49Aaron Chase:Can I share my screen with you? Sure. Screenshot. Okay, ready?
17:53Molly Webster:Whoa.
17:54Aaron Chase:It looks like whittled bone. Like white bone. It's almost like a tool.
17:59Molly Webster:Like you'd imagine like you'd find in like an archaeological site was early needles that early humans used.
18:06Aaron Chase:Yes, that'd be like early humans crafted this thing.
18:09Molly Webster:Crafted a needle out of bone. Yeah.
18:11Menno Schilthuizen:Yeah. Oh, yeah. It's beautiful if you see.
18:13Molly Webster:But the one on the top right one legit looks like an arrow.
18:17Menno Schilthuizen:Well, there are species in which the dart looks surprisingly like an arrow you've drawn when you were a kid.
18:24Molly Webster:Even like a little feathery thing that's in the back of the air, there's a little like, what do they call that?
18:29Aaron Chase:Those are like fletchings, fletchings.
18:31Menno Schilthuizen:In other species, it's more like a flat knife shape. And I've studied a species in Borneo, which is more like a hypodermic needle with holes along the side. So they're about a centimeter long.
18:44Aaron Chase:One centimeter.
18:46Menno Schilthuizen:Yeah. So, yeah, that's almost half an inch. They are present in a snail, even if they're not mating. and you can feel them crushing when you're eating a snail.
18:57Aaron Chase:So you'll be like eating snails and then you'll go, oh, just hit a love dart.
19:01Menno Schilthuizen:Well, I would. Most people wouldn't. They would just think there's something crunchy. No, yeah, you. I'm talking about you specifically, Menno. Yeah, yes. Yeah. Yes, I would.
19:11Aaron Chase:My gosh, I've never actually had snails, but now I... Okay. Well, I don't know how if I would feel if I was eating the love dart. Maybe bad?
19:19Menno Schilthuizen:Yeah. No, you eat that entire reproductive system as well, including the love dart.
19:24Molly Webster:But so the dart is not a penis. It's not like delivering sperm.
19:29Aaron Chase:The dart is not a penis. Okay. The dart plays a specific role.
19:33Menno Schilthuizen:So what they do with the love dart is they expel this dart with considerable force into the partner.
19:40Aaron Chase:Like they shoot it.
19:41Menno Schilthuizen:They shoot it. Yeah. Yeah. Some species shoot it. Some species push it. But like the escargot that we eat, it really shoots it with force and it goes fast. So there's a muscular organ that's very fast and forcefully pushes it into the skin of the partner. And in some species, it is withdrawn after that. And in other species, it's sort of a disposable dart and it stays in the body. Yeah.
20:07Aaron Chase:And where are you shooting the dart toward? Like, what do you want to hit?
20:12Menno Schilthuizen:It looks like you mostly want to hit the skin very close to that genital opening. But sometimes...
20:20Aaron Chase:So the head, the face.
20:22Menno Schilthuizen:Yeah, the cheek. Okay.
20:23Aaron Chase:And what is it doing with the dart? Is it shooting a material? Substance is just like, hey, I want your attention.
20:31Menno Schilthuizen:Well, that was a mystery until quite recently. People thought, yeah, it was some sort of stimulation. You know, just like when you see lions mating, they're also biting into each other's heads. And sharks also do that. So why not shoot a dart? It could be something like that. And then people thought maybe it's what they call a nuptial gift. So a donation of calcium to help the partner build the eggs for the offspring that they're going to produce.
21:01Aaron Chase:Because eggs use calcium?
21:03Menno Schilthuizen:Because the eggs need calcium for the shells. But then research in the 1990s showed that there was barely enough calcium in a dart to produce the shell for one egg. So that also wasn't the answer. But research by Ronald Chase and Joris Kuhne showed that there were actually hormones being delivered into the body of the snail that is being shot. Yeah, yeah, yeah.
21:32Aaron Chase:So the dark gland produces this mucus that has inside of it essentially a sex hormone. And the arrow is either covered in or full of this sticky goo.
21:45Menno Schilthuizen:These hormone-like substances get into the bloodstream of the animal that receives the dart. And it turns out that those hormones, they produce involuntary spasms in the female organs of the partner, which increases the uptake of sperm.
22:03Aaron Chase:Wow. Okay.
22:04Menno Schilthuizen:So it's a kind of manipulation.
22:06Aaron Chase:You're saying that when this hormone hits the system of the partner, what you could call the vagina, and it like makes it seize or like cramp or something?
22:18Menno Schilthuizen:It's a little bit more complicated than that, unfortunately.
22:22Aaron Chase:So it's actually that behind the vagina, there are these two pockets. One is a storage room. The other is a digestion room. And when the hormone hits and causes these like tiny spasms.
22:35Molly Webster:Sounds almost like a little orgasm or something.
22:39Aaron Chase:Yeah, but it causes muscles to contract.
22:41Menno Schilthuizen:And what the hormone does is it sort of creates or it causes the entrance of that digesting organ to close off.
22:53Aaron Chase:And it also kind of pushes sperm out of the storage chamber. And all of that can lead to the sperm, you know, being kind of pushed toward an egg.
23:05Menno Schilthuizen:So if you shoot your dart right, you probably will gain more offspring than if your dart misses its target. There's also species in Japan which don't shoot a laugh dart, but they stab multiple times. and every time they stab the dart is recharged with new hormone so they have this they sort of dip it in the glands in their body and then they push it in again and then they pull it out and dip it again and push it in again so there's a snail where this has been seen the sort of the snail would be seen stabbing its partner 3 300 times in rapid succession uh so probably it's There it's also a matter of more is better.
23:49Menno Schilthuizen:So they just keep pumping this hormone into the partner and vice versa.
23:54Aaron Chase:And the partner lived through 3 ,000 stabs.
23:56Menno Schilthuizen:Yeah. Yeah. Yeah. It's just a single, it's going into the same wound all the time. So it's not making new wounds. It's not like Caesar.
24:04Aaron Chase:Did you say it's not like Caesar? Yes.
24:09Menno Schilthuizen:So yeah, there's pictures of these snails that are mating and there's this dart is sticking through the head of one of the snails. the fletchings are still coming out on one side and the tip is coming out on the other side.
24:22Aaron Chase:So they're like visible to the naked eye.
24:24Menno Schilthuizen:Yeah, I find them in my garden after a wet night when snails have been mating. Wait, what? Yeah, they leave those darts on the floor.
24:35Aaron Chase:Wait, do you think I've seen a snail dart and just not known it?
24:39Menno Schilthuizen:Could be.
24:40Aaron Chase:And it doesn't kill it?
24:41Menno Schilthuizen:It doesn't kill it. No, they don't seem to suffer too much from it. Of course, they don't have a brain like we do that can be hit. So they just have some ganglia, which are in a different place. So maybe nothing vital is being hit.
24:55Aaron Chase:Maybe the ganglia are in a different place because they're like, we've seen these darts, we're going to move on over to the stomach.
25:00Menno Schilthuizen:I wouldn't be surprised, yeah.
25:02Aaron Chase:Man, I'm just thinking about you in your backyard, just like picking up love darts. Are you like, wow, last night was a big night.
25:08Menno Schilthuizen:Yeah, exactly. It's usually in the spring when it's warm, but rainy, when we have a spring like that, you see snails mating. And you often find these slime spots, which are sort of a telltale sign that they've been having fun. And you find these love darts lying on the floor because they do sometimes miss and sometimes they also expel them from their body after mating.
25:33Aaron Chase:How would they get it out? Like if I have a love dart through my head, how am I extracting it?
25:39Menno Schilthuizen:maybe if it's completely through you wouldn't be able to get it out but if it's sort of sticking in the skin then yeah i guess just by by movements it's wiggles out like just like a
25:50Aaron Chase:like a splinter in your skin and you as a scientist i'm assuming that love darts are interesting to you and that and that finding out how they worked is of interest to you so So, like, I'm just curious as to, like, what insights it gives you.
26:10Menno Schilthuizen:Well, what insights it gives me is that it's so abundantly clear that the evolution of reproductive organs, it's a complete madhouse of evolutionary novelties and measures and countermeasures and warfare sometimes, but also persuasion. Let's say on the male side, an evolutionary change that allows the male to bypass any control of the female. This will then immediately be followed by an evolutionary countermeasure on the female side that regains control for the females. And all these changes accumulate on top of each other and it's very unpredictable in which direction it will go. And the fact that these darts have evolved multiple times They look different in different species, that some species have one, some species have two, some species have four.
27:05Menno Schilthuizen:Some species have this disposable dart, some reuse them. Some stab once, some stab thousands of times. Some don't form darts on their first mating, but only on their second and later. So even within the darts, there's so much variety that it really drives home the fact that this genital evolution, You can see anything in evolution sort of encapsulated in what goes on in these genitals.
27:34Molly Webster:I mean, I, evolution aside, I'm just sort of, I had no, like I thought snails, maybe they just slime up next to each other and then there's a sack of eggs or something. Like I had no.
27:49Aaron Chase:Yeah, it's like you just look at these things and you think slime ball. You don't think theater of evolution.
27:54Molly Webster:No, no. Or three foot penis or. Yeah. Look at what I'd been missing this whole time.
28:00Aaron Chase:I think one of the things I'm most fascinated by is that I can see it, that like I could go pick up a little love dart. It's almost like it's almost like being it's so funny to say this to a scientist. And I do really believe in science, but it's like it's almost like being like, oh, my God, fairies do exist. Like it's like being exposed to this world that just feels so other and tiny and magical. but like there's a little remnant of it left behind. And I know that it's real because of that.
28:32Menno Schilthuizen:Yeah, and of course there's also these medieval marginalia. I don't know if you've heard about these. No, what's that? So marginalia are these little embellishments in the margins of medieval books. Okay. Where, you know, there would be little scenes of a hare or a duck or a fox chasing a bird. But there's also lots of marginalia about knights fighting with snails with swords. Really? Yeah. And people have also thought maybe that has to do with the love darts. There's a whole literature on this.
29:06Aaron Chase:So it feels like there was almost like a time of the world when we were bumping into love darts more. Yeah. Oh my God, this pet story is busy. Okay. That's that, maybe. Do you think that some scientist or some naturalist or just some person walking along millennia ago found a love dart on the ground and then made up the myth of Cupid?
29:40Menno Schilthuizen:Yeah, there is actually some people think that's how the myth of Cupid evolved. Wow.
29:47Aaron Chase:So, across the street, sniffing over an exploded bag of trash. Wait, so, could I go find a love dart?
29:58Menno Schilthuizen:Well, they're in Prospect Park in Brooklyn on trees.
30:04Aaron Chase:So, there are some local love darts?
30:06Menno Schilthuizen:Definitely. You'd have to wait for them to come out of hibernation, which would be in late April, probably. Okay. And then they usually start mating quite soon thereafter. So if you go out early in the morning and look on walls, on trees, on tree trunks, and as soon as you see two snail shells that are sitting really close together, touching each other, then they're usually mating. Then you can look from the side and then you might see a dart sticking out or maybe a dart is lying or being stuck on the slime that they're sitting on.
30:43Aaron Chase:You've given us a new thing to go. into the world and find. The ground's not thawed yet.
30:50Menno Schilthuizen:You're right. I mean, the story like this could make people go out and think, I want to see my love darts for myself and I'm going to go into the park and find snails that are mating.
31:00Aaron Chase:There's a wet tree. And they will. Not quite yet, but soon.
31:05Menno Schilthuizen:It's a miniature world that exists. This would be where you could find a snail. Or two.
31:18Thank you.
31:44Aaron Chase:edited by Alex Neeson, fact-checked by Diane Kelly, and reported by yours truly. If you want to read more about snail sex, you should go check out Menno's book called Nature's Nether Regions. There's a whole chapter on snail sex. Menno Stiltalsen is an evolutionary biologist at Leiden University in the Netherlands. Thank you, Menno. I also want to give a shout out to Aaron Chase. I first heard about love darts from Aaron very recently, and in fact, it is his dad, Ronald Chase, who discovered what the love darts were actually doing to snails. If you want to read more about how I found out about love darts, check out our newsletter or go sign up for the newsletter, which is at radiolab.org slash newsletter.
32:31Aaron Chase:For those of you who are lab members, we are dropping some snail extra content on the lab. If you are not lab members, go sign up now and you can learn all about Snug Life. And finally, you best believe that the second it thaws outside, I will be out there looking for love darts, and I'd love for you to join me. So keep an eye on social media, and we'll keep you posted. For now, I am Molly Webster. Spring is a coming. This is Radiolab. Thanks for listening.
33:04Molly Webster:Hi, I'm Gabby. I'm from San Francisco, and here are the staff credits. Radiolab is hosted by Lula Miller and Lantif Nasser. Soren Wheeler is our executive editor. Sarah Sandback is our executive director. Our managing editor is Pat Walters. Dylan Keefe is our director of sound design. Our staff includes Jeremy Bloom, W. Harry Fortuna, David Gable, Maria Paz Gutierrez, Sindhu Nainasambandan, Matt Keelty, Mona McGawker, Annie McEwen, Alex Niesen, Sarah Kari, Rebecca Rand, Anissa Vitsa, Arian Wack, Molly Webster, and Jessica Young. with help from Gabby Santis. Our fact checkers are Diane Kelly, Emily Krieger, Natalie Middleton, Anjali Mercado, and Sophie Semayi.
33:53Molly Webster:Leadership support for Radiolab's science programming is provided by the Simons Foundation and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.
34:13Molly Webster:This is Ira Flato, host of Science Friday. For over 30 years, the Science Friday team has been reporting high-quality science and technology news, making science fun for curious people by covering everything from the outer reaches of space to the rapidly changing world of AI to the tiniest microbes in our bodies. Audiences trust our show because they know we're driven by a mission to inform and serve listeners first and foremost with important news they won't get anywhere else. And our sponsors benefit from that halo effect. For more information on becoming a sponsor, visit sponsorship.wnyc.org.
From the publisher
In this episode, we consider a creature we often don’t think much about—the snail. And not just snails, but their sex lives. Which, as it turns out, is epic. There is persuasion and subterfuge, spaghetti penises and co-copulation. And this very surprising habit—erm kink—of making tiny arrows (actually!) and stabbing each other with them. Known as a “love dart,” these limestone daggers aren’t just a strange trick of nature—they have a deep evolutionary purpose.
Special thanks to Menno Schilthuizen and Aaron Chase.
EPISODE CREDITS:
Hosted by - Molly Webster
Reported by - Molly Webster
Produced by - Mona Madgavkar, Annie McEwen, Molly Webster
Sound design contributed by - Mona Madgavkar, Annie McEwen
Fact-checking by - Diane A. Kelly
and Edited by - Alex Neason
EPISODE CITATIONS:
Videos -
A love dart being DARTED! (https://zpr.io/rYhLwXhaxQQP) – Molly has watched this video so many times
Articles -
- Changes in the reproductive system of the snail Helix aspersa caused by mucus from the love dart. (https://zpr.io/xxjuCcTyiVJV) by Koene JM, Chase R. J Exp Biol.
- The snail's love-dart delivers mucus to increase paternity. By Chase R, Blanchard KC. Proc Biol Sci.
- A love-dart at the heart of sexual conflict in snails (https://zpr.io/X2ANHPaEg5sr) by Foote C
** This article has an image of eight different love darts, and it’s what Molly shows to Soren in the episode (this image is one of her favorite research finds!)
Books -
“Nature’s Nether Regions: What the Sex Lives of Bugs, Birds, and Beasts Tell Us About Evolution, Biodiversity, and Ourselves” (https://zpr.io/ktMvJbZciCdD) by evolutionary biologist Menno Schilthuizen.
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Leadership support for Radiolab’s science programming is provided by the Simons Foundation and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.




