Sperm Tales

Summary

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Radiolab: "Sperm Tales"

Date: October 7, 2008
Hosts: Jad Abumrad, Robert Krulwich
Guests: Joanna Ellington (fertility expert), Tim Birkhead (biologist, University of Sheffield), Harry Moore (sperm biologist)

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Episode Overview

In this Radiolab "tidbit" episode, hosts Jad Abumrad and Robert Krulwich present a sneak preview of an upcoming full episode dedicated to the science, mystery, and mayhem of sperm. Through conversations with leading experts, the hosts explore the astonishingly complex, competitive, and occasionally cooperative world of sperm—dispelling myths and revealing bizarre true facts about human and animal reproduction. The tone is playful, curious, and often humorous as they journey from human sperm oddities to remarkable discoveries in the animal kingdom.

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Key Discussion Points & Insights

1. Why Spend a Show on Sperm?

• [01:49] Robert frames the episode as a lighthearted but tantalizing teaser for an upcoming in-depth feature on sperm, noting, "Why would you spend so much time talking about that?" Jad adds, jokingly, "it's a very sad, sad, lonely show."
• The show promises unexpected insights from a deep dive into an ostensibly simple topic, living up to Radiolab’s trademark of finding fascination in small details.

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2. How Many Sperm ‘Make the Cut’?

Interview with Joanna Ellington, Fertility Expert

• [02:22] Robert asks, if you’re “a healthy male at the top of your game... what proportion of your gang would be fit and ready to do the deed?”
• [02:50] Joanna reveals:
  • Only 14% (or more) of sperm are normally shaped in a healthy ejaculate; meaning 86% are abnormally shaped.

    "A normal ejaculate from a man is if you have 14—one-four—14% or more of the sperm that are normally shaped. That's a very low percent." (Joanna Ellington, 02:50)

• [03:06] Abnormal sperm may have:
  • Defective tails (can’t swim, go in circles, swim slowly)
  • Tails that are knotted or fail to unwind
  • Large, round "balloon head" (Globospermia)
  • Holes in the DNA (vacuoles)
  • Two tails, double or triple heads
  • Many are completely immobile (dead)

    "Some of them swim in a circle... some going slowly... some of them are going to be dead and not moving at all." (Joanna Ellington, 03:15-04:32)

• [04:36] Joanna summarizes that there are "hundreds of little enumerations that could go wrong" as sperm attempt to reach the egg:

  "If you were to actually write down everything that could go wrong with sperm... it would be hundreds of little enumerations..." (Joanna Ellington, 04:36)

Notable quote:

"But that's why men make sperm all the time. They constantly are making it. They constantly have a fresh supply." (Joanna Ellington, 04:43)

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3. Sperm Competition vs. Sperm Cooperation

• Jad marvels at the odds, lamenting "the odds are not in our favor" [05:20]; Robert reinforces that this is “when you’re healthiest”.
• The public imagination (and pop culture) envisions sperm as competitors—racing to the prize.

  "The public image here is that every guy that you put in is, in a Woody Allen movie sense, competing against his neighbor." (Robert Krulwich, 05:36)

• But the hosts tease a twist: a surprising level of sperm cooperation in some animals.

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4. Remarkable Sperm: The Wood Mouse Case

Story from Tim Birkhead (Biologist) and Harry Moore (Sperm Biologist)

• [05:58] Biologist Tim Birkhead and his colleague Harry Moore become curious after Moore’s cat brings in a wood mouse with "large testicles."

• [06:56] Examination reveals:

  • All rodents have sperm with slightly hooked heads, but the wood mouse’s hook is “extreme.”

    "The hook bends right back and touches the head again... it looked as though the hook was a specific adaptation to grasp the tails of other sperm." (Harry Moore, 06:56–07:15)

• [07:24] Experiment: Placing wood mouse sperm in special medium, Moore observes them forming “sperm trains,” gripping each other head to tail.

  "The sperm all joined up together in what he called sperm trains." (Harry Moore, 07:24) "It's a bit like spaghetti moving forward." (Harry Moore, 07:42)

• [07:45] Measurement shows these sperm trains move twice as fast as single sperm.

• Robert asks, if sperm cooperate, “Who gets to be the daddy sperm?”

• [08:08] Moore explains: Some sperm self-sacrifice (undergo the “acrosome reaction,” losing fertilization ability) to free others—allowing a “vanguard” to fertilize the egg.

  "They give up for their brethren." (Robert Krulwich, 08:21)
  "Yeah, that's exactly it." (Harry Moore, 08:24)

• [08:36] The sperm in a train are from the same male and share genetic interests, making sacrifice evolutionarily sensible.

  "All those sperm are related, so they all have more or less a common interest." (Harry Moore, 08:36)

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5. Reflection & Teaser for Full Episode

• The hosts reflect on how surprising and “novel” it is to find sperm that cooperate rather than only compete.

  "The idea that a sperm would sacrifice itself for a brother sperm is very novel when you think about how normally this is thought of as such a competitive event." (Robert Krulwich, 08:50)

• They reiterate their excitement for listeners to hear the full episode in the coming weeks.
• Closing banter and plugging Radiolab’s website.

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Memorable Moments & Quotes

• On sperm abnormalities:

  "Are there double headed ones?" (Robert Krulwich, 04:22)
  "Yes, absolutely." (Joanna Ellington, 04:23)

• On the competitive myth:

  "So it's Jerry versus Ted versus Andy versus Mark versus Freddy versus Billy and they're all rushing to the goal." (Robert Krulwich, 05:36)

• On sperm trains:

  "When he measured the speed at which the sperm trains moved, it was about twice that of isolated sperm." (Harry Moore, 07:45)
  "They all joined up together in what he called sperm trains." (Harry Moore, 07:24)

• On sperm sacrifice:

  "Some of the sperm undergo what's called the acrosome reaction... those sperm can no longer fertilise, but they free a vanguard of sperm that then can fertilize." (Harry Moore, 08:08)
  "They give up for their brethren." (Robert Krulwich, 08:21)

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Important Timestamps

• 01:49: Introduction to the “sperm tidbit”
• 02:22–05:13: Discussion with Joanna Ellington about sperm morphology and fertility odds
• 05:36: Public image of sperm as competitors
• 05:58–06:56: Mouse sperm anecdote begins
• 07:24–08:24: Discovery and implications of “sperm trains” and cooperation in wood mice
• 08:36–09:15: Summing up—sperm cooperation and implications

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Takeaway

This Radiolab episode teases the complexity and wonder of sperm biology, upending the classic narrative of ruthless individual competition with surprising tales of cooperation and sacrifice. Through clever storytelling and expert voices, the episode leaves listeners eager for the deeper dive to come.

Transcript

[Jad Abumrad]

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[Jad Abumrad]

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[Michaels Shop Announcer]

You're listening to Radio, the podcast from at Public Radio, Public Radio, WNYC and npr.

[Jad Abumrad]

Hello, I'm Jad Abumrad.

[Robert Krulwich]

Hello, I'm Robert Quillworth.

[Jad Abumrad]

This is Radiolab, the podcast, which means.

[Robert Krulwich]

It'S not the broadcast.

[Jad Abumrad]

Not the one hour show.

[Robert Krulwich]

No, not the one hour show.

[Jad Abumrad]

This is like a little tidbit.

[Robert Krulwich]

This is a tidbit, but this is a tidbit with a teasing purpose because we have in the next few weeks we are going to do the real shows about race and there's one about choice. There's one, however, entirely devoted to the subject of sperm. And sperm. You think, well, why would you spend so much time talking about that?

[Jad Abumrad]

Yes. In fact, it's a very sad, sad, lonely show. Anyhow, go on.

[Robert Krulwich]

We learn a lot of I mean, if you open up any little basket and ask too many questions, you learn all kinds of fascinating things.

[Jad Abumrad]

So true. Particularly with sperm.

[Robert Krulwich]

Yes. So we talked when we were preparing this hour with a woman named Joanna Ellington, a fertility expert who runs a company with a very short name, kind of like Sperm Itself ing I N G it's a fertility firm, and I asked her if you are a healthy male at the very top of your game. So you got everything you're ever going to have, and they're all frisky little guys ready to go. What proportion of your gang would be fit and ready to do the deed?

[Joanna Ellington]

A normal ejaculate from a man is if you have 14, 1 4, 14% or more of the sperm that are normally shaped. That's a very low percent.

[Robert Krulwich]

And 86% are abnormally shaped.

[Joanna Ellington]

Yeah.

[Robert Krulwich]

How do they differ from the normal?

[Joanna Ellington]

Typically, you're gonna have problems with the tail. And then that makes it so they can't swim. Right. They swim in a circle, can't swim fast.

[Robert Krulwich]

Some of them swim in a circle.

[Jad Abumrad]

Mm.

[Robert Krulwich]

You mean when they go bang and off you go, they just go round and round and round and round.

[Joanna Ellington]

Right. And that doesn't work very well, of course.

[Robert Krulwich]

Okay. Circles, slow. Anything else?

[Joanna Ellington]

Yeah. As the sperm get ready to be ejaculated, the tail unwinds from around the cell. And sometimes it doesn't unwind. Right. It stays wound up or the very tip of the tail stays kind of in a knot, I guess you could say, basically.

[Robert Krulwich]

So you got a knot on your tail?

[Joanna Ellington]

Yeah.

[Robert Krulwich]

Okay, so we got some stalled out, some going in circles, some going slowly. Are there horror mutant sperm?

[Joanna Ellington]

Yeah, there's one called Globospermia and that is a very large round head. It's maybe three or four times normal size. And instead of having that oval, it's just quite round looking.

[Robert Krulwich]

That's like a balloon head. Big fat balloon head.

[Joanna Ellington]

Yeah, exactly. You can have sperm that have vacuoles, which are basically holes in the DNA. You can have sperm that have two tails. Ooh, yeah.

[Robert Krulwich]

Isn't that better?

[Joanna Ellington]

No. You don't want anything abnormal.

[Robert Krulwich]

Are there double headed ones?

[Joanna Ellington]

Yes, absolutely.

[Robert Krulwich]

Are there triple headed ones?

[Joanna Ellington]

Probably some.

[Robert Krulwich]

This is making me nervous. Anything else?

[Joanna Ellington]

Some of them are going to be dead and not moving at all.

[Robert Krulwich]

Well, that's a problem.

[Joanna Ellington]

Yeah. In addition to that, there's many, many microbiochemical things that they have to go through. So if you were to actually write down everything that could go wrong with sperm as it goes to meet the eggs, it would be hundreds of little enumerations that could go wrong. But that's why men make sperm all the time. They constantly are making it. They constantly have a fresh supply. You've got to have something that can go through all the hurdles and all the barriers and make sure at the end of the day that you have the best, healthiest sperm cell that's participating in making a baby.

[Robert Krulwich]

When you Say gad that it's lonely, sad with odds like that. Remember, this is when you're healthiest.

[Jad Abumrad]

I know.

[Robert Krulwich]

When you're healthy as well.

[Jad Abumrad]

What I don't get though is like, how does it, how does it. Well, this is what we're gonna go into the show, but I'll just ask you now, how does it happen, given all of those potential pitfalls and that every sperm is outracing the other sperm as well.

[Robert Krulwich]

The public image here is that every guy that you put in is, in a Woody Allen movie sense, competing against his neighbor. So it's Jerry versus Ted versus Andy versus Mark versus Freddy versus Billy and they're all rushing to the goal.

[Jad Abumrad]

And what if Jerry and Ted and Mark and Fer and Billy are all.

[Robert Krulwich]

Double headed with well, then they don't make it.

[Jad Abumrad]

So it's. The odds are not in our favor.

[Robert Krulwich]

But there is a level of cooperation we discovered while doing this hour that was deeply surprising. Sperm are not always about competing against each other. And this we learned from Tim Burkhead, who's a biologist at the University of Sheffield. He told us the story about. It was a wood mouse, a W o o.

[Jad Abumrad]

Not a could mouse.

[Robert Krulwich]

Not a could mouse or a should. No, not a should mouse. This is a wood mouse. Yes, wood mouse, which is a gift wood mouse.

[Harry Moore]

My colleague Harry Moore, who's a sperm biologist here in Sheffield, his cat brought in a wood mouse, laid it on the dining room floor and he looked at it and thought, gosh, that's got large testicles. He dissects it.

[Robert Krulwich]

Unusual reaction to a cat's gift that I've heard in a long time. I'll say, you know, if you're a testicle guy, you're a testicle guy.

[Jad Abumrad]

You want to take a closer look?

[Robert Krulwich]

Anyway, so he dissects the, he dissects the mouse and then carefully removed the sperm inside. And then he looked at the shape of the sperm. This was interesting.

[Harry Moore]

All rodents, the sperm has a slightly hooked shaped head. But in the wood mouse, that hook is extreme, so much so that the hook bends right back and touches the head again. What Harry noticed was that it looked as though the hook was a specific adaptation to grasp the tails of other sperm.

[Robert Krulwich]

This sperm on its head was a kind of grasping hook, which suggested that maybe this sperm wanted to, to hold hands with something.

[Harry Moore]

Harry put the sperm into a kind of special sperm medium. And to his amazement, the sperm all joined up together in what he called sperm trains.

[Robert Krulwich]

Sperm T R A I N S.

[Harry Moore]

Yes, like in a railway train. The Tails of other sperm were held by this hook.

[Jad Abumrad]

And it's just head to tail. Head to tail.

[Harry Moore]

It looks. It's a bit messy. It's a bit like spaghetti moving forward.

[Jad Abumrad]

Okay.

[Harry Moore]

The amazing thing is when he measured the speed at which the sperm trains moved, it was about twice that of isolated sperm.

[Robert Krulwich]

But wait a second. If me and 700 others of us or 10 of us get together at the head and swim together, our tails all increasing our speed, who gets to be the daddy sperm?

[Harry Moore]

In the wood mouse, some of the sperm undergo what's called the acrosome reaction, releasing this hook. And when that happens, those sperm can no longer fertilise, but they free a vanguard of sperm that then can fertilize.

[Robert Krulwich]

And then they give up for their brethren.

[Harry Moore]

Yeah, that's exactly it.

[Robert Krulwich]

Whoa. So then it's not fair to say that down there at the sperm level, it's every sperm for himself. In a few cases, the sperm is there for the other guy.

[Harry Moore]

Yeah, but they're all part of the same ejaculate. All got roughly the same genetic makeup. All those sperm are related, so they all have more or less a common interest.

[Jad Abumrad]

See, we help each other out.

[Robert Krulwich]

Yeah, I mean, this is different. However, it is at this point, just specific to the wood mouse. So woodmouse sperm seem to have a thing going on amongst themselves. And the idea that a sperm would sacrifice itself for a brother sperm is very novel when you think about how normally this is thought of as such a competitive event.

[Jad Abumrad]

That's right. Well, in any case, we hope you'll tune in for that show. It's coming up in about a month and a half.

[Robert Krulwich]

It's not really a month and a half. If you're listening to this late in the week, it's a month and two weeks from now. Okay, it's a month and two. It's a month. It's so short. It's really five weeks from now going on four weeks, and before you know it, it'll be three weeks.

[Jad Abumrad]

Do you see what I deal with? Soren, can you take him down, please?

[Robert Krulwich]

You can't take me down.

[Jad Abumrad]

Just pot him down, please. Any case, so Visit our website, Radiolab.org, you can find out more about anything on our website. And also, we should say, we should give thanks. We are funded by the Corporation for Public Broadcasting. Hey, take him down. The National Science foundation and the Alfred P. Sloan foundation, who this month is honoring Flash of Genius, the winner of the 2008 feature feature film prize in Science and Technology at the Hamptons International Film Festival. I'm Jad Abumrad. Okay, you can put him back up now.

[Robert Krulwich]

Albert Krulwich.

[Jad Abumrad]

We'll see you soon.

[Robert Krulwich]

Very soon.

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