WEBVTT - The Lesser of Two Crab Claws, Part 2

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<v Speaker 1>Hey you welcome to Stuff to Blow your Mind. My

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<v Speaker 1>name is Robert.

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<v Speaker 2>Lamb and I'm Joe McCormick, and it's Saturday. We are

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<v Speaker 2>bringing you an episode from the vault. This one originally

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<v Speaker 2>published on June thirtieth, twenty twenty two, and it's part

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<v Speaker 2>two of our series The Lesser of Two Crab Claws,

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<v Speaker 2>about asymmetry in the natural world.

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<v Speaker 3>Enjoy Welcome to Stuff to Blow Your Mind, a production

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<v Speaker 3>of iHeartRadio.

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<v Speaker 1>Hey, welcome to Stuff to Blow your Mind. My name

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<v Speaker 1>is Robert Lamb.

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<v Speaker 2>And I'm Joe McCormick, and we're back with part two

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<v Speaker 2>of our series on asymmetry in life. Now. In the

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<v Speaker 2>last episode, we talked about the concept of bilateral symmetry,

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<v Speaker 2>where basically all of the higher animals have body plans

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<v Speaker 2>where the left and the right sides are more or

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<v Speaker 2>less a copy of one another. In other words, along

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<v Speaker 2>one of the three dimensions of space, our bodies are

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<v Speaker 2>approximately mirrored, at least on the outside. Now, in most organisms,

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<v Speaker 2>there are minor variations on this type of symmetry, but

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<v Speaker 2>occasionally there are species with isolated but radical deviations, where

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<v Speaker 2>like one feature on the outside of an otherwise mirror

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<v Speaker 2>flipped half of the body is drastically different from what

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<v Speaker 2>you find on the other side. Examples that came up

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<v Speaker 2>last time were the tusk of the nar wall, where

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<v Speaker 2>in most cases it's actually the left maxillary canine tooth

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<v Speaker 2>so weird it's the left fang basically of this whale

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<v Speaker 2>stabbing through the upper lip and it becomes a single tusk.

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<v Speaker 2>We also talked about the blowholes and skulls of toothed whales,

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<v Speaker 2>such as the sperm whale, where in many cases these

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<v Speaker 2>have developed left right mismatches that seem to have evolved

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<v Speaker 2>to support the capacity for echolocation. We also talked about

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<v Speaker 2>the cock eyed squid, which has two extremely different eyes

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<v Speaker 2>for looking into extremely different worlds, one for the water above,

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<v Speaker 2>which is filtering sunlight, and one for the water below,

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<v Speaker 2>which may contain flashes of bioluminescence. And so today we

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<v Speaker 2>wanted to pick up the series by talking about some

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<v Speaker 2>more fascinating examples of lopsided animal evolution. Animals with halves

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<v Speaker 2>that mostly match but in one capacity or another do not,

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<v Speaker 2>and why that would be. Now, there are many great

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<v Speaker 2>examples of asymmetrical evolution incrustations, and we may actually save

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<v Speaker 2>some of these for the next part in the series.

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<v Speaker 2>I know we're going to go to at least three

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<v Speaker 2>parts here, but for today's episode, I wanted to start

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<v Speaker 2>by getting out the lemon and the drawn butter, because

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<v Speaker 2>this is an asymmetry that you don't have to be

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<v Speaker 2>a specialist a marine biologist to notice for yourself. If

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<v Speaker 2>you've ever eaten, or even just seen a cooked lobster,

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<v Speaker 2>you probably have noticed a weird mismatch between the lobster's

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<v Speaker 2>two claws. Rob, I assume you've you've seen this for yourself.

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<v Speaker 1>Yes, yes, they're not not as recently as you have.

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<v Speaker 1>Because I believe this this was the inspiration for this episode. Right,

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<v Speaker 1>you recently ate a lobster?

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<v Speaker 2>Oh, I don't. I don't think I even told you that,

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<v Speaker 2>But yeah, this probably had something to do with it.

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<v Speaker 2>I can't confirm the inner workings of my subconscious mind.

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<v Speaker 2>But not too long ago, I was in the I

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<v Speaker 2>was in New England where where lobster is king. I'm

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<v Speaker 2>not gonna do the accent, but lobster is king. And

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<v Speaker 2>I did. I did, in fact eat a lobster, and yeah,

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<v Speaker 2>and I noticed stark differences between the claws, even not

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<v Speaker 2>just looking at them, but in my fingers, you know,

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<v Speaker 2>one claw was sort of a pleasure to crack open

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<v Speaker 2>and get the meat out of, and the other one.

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<v Speaker 2>When I handled the inside of the pincers, they were

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<v Speaker 2>much sharper, and the spines within them were much smaller

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<v Speaker 2>and kind of were irritating and unpleasant to the fingers.

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<v Speaker 1>Fascinating.

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<v Speaker 2>So what's going on with this claw mismatch? Oh and

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<v Speaker 2>by the way, we should be clear that we're talking

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<v Speaker 2>specifically about the American lobster or Homarus americanas this is

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<v Speaker 2>the lobster you find along the northern edge of the

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<v Speaker 2>eastern coast of North America, so all up through like

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<v Speaker 2>the north half of the eastern United States and up

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<v Speaker 2>into Canada.

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<v Speaker 1>This is like the red lobster lobster, the lobster from

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<v Speaker 1>your grocery store that has rubber bands on its claws,

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<v Speaker 1>not like the Caribbean lobster.

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<v Speaker 2>Yeah, not the rock lobster, though I hear those can

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<v Speaker 2>be good eating too. I've never had man. But anyway,

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<v Speaker 2>so the American lobster. So you look at these two claws,

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<v Speaker 2>and what you'll notice is that usually one claw is

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<v Speaker 2>longer and flatter, with a longer I don't know what

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<v Speaker 2>the technical term for this is the danger zone, the

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<v Speaker 2>space between the two pincers and the insides of the

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<v Speaker 2>pincers on this flatter, longer claw seem to be sharper,

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<v Speaker 2>more like a kind of spiky pair of scissors. And

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<v Speaker 2>then the other claw is shorter in length but bulkier,

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<v Speaker 2>thick with muscle, and the inside edges of its pincers

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<v Speaker 2>have a sort of rounder, larger grain texture, almost pebbled,

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<v Speaker 2>rather than with tiny spines. These claws are commonly referred

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<v Speaker 2>to as the cutter and the crusher, respectively. I think

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<v Speaker 2>the cutter is sometimes called the pincher also, But yeah,

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<v Speaker 2>they are what they sound like, the cutter and the crusher.

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<v Speaker 2>So what's going on? Why the two different claws on

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<v Speaker 2>the same lobster? How does a lobster end up with

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<v Speaker 2>two very different claws and what are they for? Well,

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<v Speaker 2>to answer this question, I was reading what I thought

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<v Speaker 2>was a really interesting older article in American Scientist magazine.

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<v Speaker 2>So this is from nineteen eighty nine by an author

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<v Speaker 2>named C. K. Govind who was a professor of zoology

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<v Speaker 2>at the University of Toronto, and it's called asymmetry in

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<v Speaker 2>Lobster claws. Seems like a lot of Govin's research focused

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<v Speaker 2>on crustaceans, and so Govin begins by pointing out a

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<v Speaker 2>number of different examples of asymmetry and animals. He talks

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<v Speaker 2>about lateral dominance or handedness in humans and even mentions

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<v Speaker 2>I thought this was interesting. In some songbirds, such as canaries,

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<v Speaker 2>you have bilateral asymmetry in their singing apparatus. Song production

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<v Speaker 2>seems to be centered on structures in the left half

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<v Speaker 2>of the syrinx, And so when you see asymmetries like this,

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<v Speaker 2>you can ask all kinds of questions about them. But

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<v Speaker 2>one thing is that you might just assume them to

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<v Speaker 2>be permanent, fixed features of anatomy, hard coded by genes

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<v Speaker 2>and express through early development. But it's interesting that there

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<v Speaker 2>are some cases where asymmetry in an animal's body seems

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<v Speaker 2>to be reversible. Just for one example, In some cases

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<v Speaker 2>of lateral dominance, damage to the dominant side of the

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<v Speaker 2>brain or body can cause the non dominant side to

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<v Speaker 2>assume some functionality previous localized to the side that has

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<v Speaker 2>now been incapacitated, and this can lead us to wonder

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<v Speaker 2>how do these asymmetries develop in the first place. So

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<v Speaker 2>Govind argues that by examining the lobster, and this is

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<v Speaker 2>the American lobster Homarus americanas we can see an example

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<v Speaker 2>of a symmetry emerging not purely as a result of

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<v Speaker 2>genetic coating, but actually as a result of how the

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<v Speaker 2>lobster interacts with its environment during a crucial early period.

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<v Speaker 2>And this is what brings us back to the crusher

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<v Speaker 2>claw and the cutter claw. So I want to read

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<v Speaker 2>from Govin's introduction here quote. As any self respecting gourmet knows,

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<v Speaker 2>the paired claws of the American lobster have decidedly different morphologies.

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<v Speaker 2>One claw, called the crusher or major claw, is short, stout,

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<v Speaker 2>and heavy, with molar like teeth on its biting surface.

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<v Speaker 2>I think that's a good comparison, molar like teeth. It's

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<v Speaker 2>the pebbles are like your back teeth. It's hard to

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<v Speaker 2>imagine them snipping something off. Instead, it's like they would

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<v Speaker 2>sort of grab hold of it and be able to

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<v Speaker 2>smash it real good.

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<v Speaker 1>Yeah. When I'm looking at a picture of this, I

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<v Speaker 1>can't help but imagine the lobster putting on a puppet

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<v Speaker 1>show with just its pincher and its crusher and each

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<v Speaker 1>of them have you know, different characters like like hey

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<v Speaker 1>on the crutcher, Hey on the pincher, and they interact.

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<v Speaker 2>You know, definitely the cutter claw has the higher voice.

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<v Speaker 1>Yeah.

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<v Speaker 2>Yeah, Let's say if they're street fighter characters, crusher claw

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<v Speaker 2>is zangief and cutter claw is is what maybe maybe embison?

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<v Speaker 1>Yeah yeah maybe so longer does.

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<v Speaker 2>That cheap spinning move? Yeah? Okay, So anyway, so that's

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<v Speaker 2>what that is. That that's the molar teeth on the

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<v Speaker 2>biting surface. But then, to continue the quote, the other

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<v Speaker 2>called the cutter or minor claw is long and slender

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<v Speaker 2>with incisor like teeth or your incisors are your front teeth,

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<v Speaker 2>the ones that you use to bite off things, you know,

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<v Speaker 2>not to mash them up, but to separate them from

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<v Speaker 2>what they're originally stuck to and pull them into your mouth.

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<v Speaker 2>They're for cutting. So what Govind writes is quote what

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<v Speaker 2>the gourmet might may not know, and what lobstermen know

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<v Speaker 2>painfully well, is that the cutter claw can give a quick,

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<v Speaker 2>nasty pinch. Indeed, it's dactyl, meaning the part of the

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<v Speaker 2>claw that moves, the closing part can close against the

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<v Speaker 2>opposing polyx within twenty milliseconds, which is several times faster

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<v Speaker 2>than any human reflex. In contrast, the crusher claw closes

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<v Speaker 2>very slowly, but with enough force to crack open the

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<v Speaker 2>shells of oysters, muscles, and other bivalves. And it's true,

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<v Speaker 2>molluscs such as muscles are a big source of food

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<v Speaker 2>prey for the American lobster. So it crawls along the

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<v Speaker 2>ocean floor in its adult phase, and what does it eat. Well,

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<v Speaker 2>it might eat some worms of various types and stuff,

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<v Speaker 2>but it's really going to be looking for mollusks such

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<v Speaker 2>as muscles. It wants to crack those shells open and

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<v Speaker 2>get that meat inside. Also, while we're mentioning anatomy, this

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<v Speaker 2>is unrelated, but I just have to say American lobsters

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<v Speaker 2>pe out of their faces. You kind of can't bring

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<v Speaker 2>lobsters up without mentioning that they face pee, and they

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<v Speaker 2>face peece specifically at each other, whether it's a mate

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<v Speaker 2>or rival. So lobster sees another lobster, they're probably going

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<v Speaker 2>to be peeing out of their faces at them. Though,

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<v Speaker 2>is best I can tell. The face peeing is symmetrical.

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<v Speaker 1>Okay, well that's good to know, But coming.

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<v Speaker 2>Back to the claws. So the difference in the speed

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<v Speaker 2>of pinching between the two claws is evidence of an

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<v Speaker 2>underlying difference, and not just the shape of the claw,

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<v Speaker 2>but its muscular composition. These claws have different types of

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<v Speaker 2>muscle in them. About ninety percent of the space of

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<v Speaker 2>a lobster's claw is taken up by the closer muscle.

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<v Speaker 2>This is the muscle responsible for bringing the pincers together.

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<v Speaker 2>Only a relatively tiny muscle is devoted to opening the claw,

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<v Speaker 2>which is why a lobster might be able to pinch

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<v Speaker 2>with massive force, but a simple rubber band can render

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<v Speaker 2>its claw harmless by holding it closed. It has way

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<v Speaker 2>more strength for closing than it does for opening.

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<v Speaker 1>I think that's a great point.

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<v Speaker 2>Yeah, I didn't double check this, but I just remembered

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<v Speaker 2>hearing a fact that may or may not be true

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<v Speaker 2>about alligator and crocodilian jaws like that when I was

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<v Speaker 2>a kid. That you know, So they can close their

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<v Speaker 2>jaws with massive force, but you can actually quite easily

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<v Speaker 2>hold their jaws together and they can't open them back up.

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<v Speaker 1>Oh, so this would be the secret of the feet

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<v Speaker 1>of the crocodile or alligator wrestler. Yes, Okay, Now coming

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<v Speaker 1>back to the lobster, does that mean that the closer

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<v Speaker 1>muscle is the delicious part? This is like that prize

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<v Speaker 1>sliver of meat from the claw.

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<v Speaker 2>Well, I don't know about relative flavors. The closer would

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<v Speaker 2>be the big one, and the opener is obviously you know,

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<v Speaker 2>it's like ten percent. It's like one ninth the size

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<v Speaker 2>of the closer muscle. So I don't know exactly what

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<v Speaker 2>you're getting. When you have a cooked lobster and you

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<v Speaker 2>pull it out of there and eat it, you probably

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<v Speaker 2>some combination of the two.

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<v Speaker 1>Well, I guess in my experience, like the bigger the

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<v Speaker 1>meat you pull out of a crustacean, like the greater

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<v Speaker 1>the sense of victory. Yeah, And likewise, the more that

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<v Speaker 1>one is picking through the crustacean with and removing tiny

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<v Speaker 1>slivers to consume, the delicious they may be. But the

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<v Speaker 1>more I feel like I'm some sort of like a

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<v Speaker 1>creature stooped on a primordial shore scavenging pieces from a

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<v Speaker 1>dead animal.

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<v Speaker 2>Getting the pieces from the tiny legs and the tiny

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<v Speaker 2>parts makes you feel more like it's the road, you know,

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<v Speaker 2>like looking for seeds or something to eat.

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<v Speaker 1>But pulling out that big piece of claw meat. You

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<v Speaker 1>feel like a king.

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<v Speaker 2>That's right, that's luxury. Okay, So you got these different muscles.

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<v Speaker 2>You got the closer muscle, the opener muscle. What makes

0:12:37.160 --> 0:12:40.120
<v Speaker 2>the difference in the speed of pinching between the crusher

0:12:40.160 --> 0:12:43.400
<v Speaker 2>claw and the cutter claw is the type of muscle

0:12:43.520 --> 0:12:47.160
<v Speaker 2>fiber that the closing muscle is composed of. The cutter

0:12:47.280 --> 0:12:51.200
<v Speaker 2>claw is made of about ninety percent fast muscle fiber,

0:12:51.240 --> 0:12:53.680
<v Speaker 2>which is exactly what it sounds like. It's designed to

0:12:54.000 --> 0:12:58.320
<v Speaker 2>move quickly along with what Govind calls a quote small

0:12:58.520 --> 0:13:02.560
<v Speaker 2>ventral band of slow muscle, whereas the crusher claw is

0:13:02.679 --> 0:13:06.640
<v Speaker 2>almost entirely or not almost, I think is entirely one

0:13:06.720 --> 0:13:09.679
<v Speaker 2>hundred percent slow muscle fiber. So it closes more slowly,

0:13:09.840 --> 0:13:13.080
<v Speaker 2>but can close with incredible force. And as a result,

0:13:13.120 --> 0:13:16.840
<v Speaker 2>cutter snaps fast and sharp. Crusher closes slowly, but but

0:13:17.000 --> 0:13:21.480
<v Speaker 2>it's massive. So you could compare this to handedness in humans,

0:13:21.600 --> 0:13:24.760
<v Speaker 2>but Govind notes that while the majority of humans are

0:13:24.840 --> 0:13:29.400
<v Speaker 2>right handed, the distribution of claws on adult lobsters seems

0:13:29.559 --> 0:13:32.640
<v Speaker 2>equally probable both ways. It's not like the crusher claw

0:13:32.720 --> 0:13:35.840
<v Speaker 2>is always on the left side. It's it's a coin flip.

0:13:35.880 --> 0:13:39.600
<v Speaker 1>Which, which would mean that there's that natural selection is

0:13:39.640 --> 0:13:41.520
<v Speaker 1>not pushing it one way or the other.

0:13:41.880 --> 0:13:44.280
<v Speaker 2>Right, it's not, I mean it's push. It's clearly pushing

0:13:44.400 --> 0:13:47.120
<v Speaker 2>the lobsters to have two different types of claws for

0:13:47.160 --> 0:13:50.000
<v Speaker 2>the asymmetry to exist. But it doesn't seem to matter

0:13:50.080 --> 0:13:53.199
<v Speaker 2>which side is which, at least not in a way

0:13:53.240 --> 0:13:57.079
<v Speaker 2>that's universal across lobsters. It is it is decided by

0:13:57.200 --> 0:14:02.040
<v Speaker 2>each individual lobster in development. So a great question then is, Okay,

0:14:02.040 --> 0:14:05.319
<v Speaker 2>if the bilateral asymmetry is individual to each lobster and

0:14:05.360 --> 0:14:09.439
<v Speaker 2>it's a random coin flip at least from a statistical

0:14:09.520 --> 0:14:12.200
<v Speaker 2>point of view, what causes the change? How does the

0:14:12.480 --> 0:14:18.160
<v Speaker 2>individual lobster's body when it's growing pick which side becomes which. Well,

0:14:18.200 --> 0:14:21.680
<v Speaker 2>we can look at lobster larval development to see this.

0:14:21.760 --> 0:14:24.360
<v Speaker 2>So when they're tiny little things swimming around before they

0:14:24.480 --> 0:14:27.480
<v Speaker 2>become the big lobster, as we recognize, during the early

0:14:27.600 --> 0:14:31.000
<v Speaker 2>larval stages, the claws of the lobster are undifferentiated. They're

0:14:31.000 --> 0:14:35.280
<v Speaker 2>exactly the same. Both claws have what Govind calls quote

0:14:35.320 --> 0:14:39.840
<v Speaker 2>a central band of fast fibers sandwiched dorsally and ventrally

0:14:39.880 --> 0:14:44.440
<v Speaker 2>by slow fibers. Then during the later juvenile stages this

0:14:44.480 --> 0:14:47.640
<v Speaker 2>would be like the fourth and fifth molting stages, there

0:14:47.680 --> 0:14:50.840
<v Speaker 2>begins to be some variability in the amount of slow

0:14:50.880 --> 0:14:53.880
<v Speaker 2>and fast fibers in each claw. But then the changes

0:14:53.960 --> 0:14:58.720
<v Speaker 2>really start to become apparent during the sixth stage of molting. Quote,

0:14:58.960 --> 0:15:01.960
<v Speaker 2>when the putative crush sure claw becomes slightly shorter and

0:15:02.040 --> 0:15:05.440
<v Speaker 2>stouter with a central molar like tooth, while the putative

0:15:05.480 --> 0:15:09.080
<v Speaker 2>cutter claw remains long and slender with a central incisor

0:15:09.280 --> 0:15:12.680
<v Speaker 2>like tooth. A corresponding asymmetry in the composition of the

0:15:12.680 --> 0:15:15.880
<v Speaker 2>closer muscle also develops. The muscle of the cutter claw

0:15:15.960 --> 0:15:20.200
<v Speaker 2>gradually acquires fast fibers by transforming the slow fibers of

0:15:20.240 --> 0:15:23.400
<v Speaker 2>most of its cross sectional face. The exception is a

0:15:23.480 --> 0:15:27.320
<v Speaker 2>ventral band. The muscle of the crusher claw gradually transforms

0:15:27.360 --> 0:15:30.960
<v Speaker 2>all of its fast fibers to slow fibers. In succeeding

0:15:31.040 --> 0:15:35.200
<v Speaker 2>juvenile development, the paired claw's further diverge toward well defined

0:15:35.240 --> 0:15:38.840
<v Speaker 2>cutter and crusher claws. So the divergence happens sometime in

0:15:38.880 --> 0:15:41.760
<v Speaker 2>the childhood of a lobster, sometime around its fourth and

0:15:41.800 --> 0:15:45.080
<v Speaker 2>fifth molting stages and really starts to appear during the

0:15:45.120 --> 0:15:49.160
<v Speaker 2>sixth molting. But then Govin mentioned something I thought was

0:15:49.200 --> 0:15:51.680
<v Speaker 2>really intriguing, an experiment going all the way back to

0:15:51.840 --> 0:15:55.960
<v Speaker 2>nineteen o eight, way back to a researcher named Victor Immel,

0:15:56.520 --> 0:15:59.760
<v Speaker 2>who found that if you remove one of the lobster's

0:15:59.760 --> 0:16:02.280
<v Speaker 2>claw during the fourth or fifth stage, so you just

0:16:02.360 --> 0:16:05.760
<v Speaker 2>pull that claw off, the claw that is left behind,

0:16:05.920 --> 0:16:10.200
<v Speaker 2>still attached to the lobster, always becomes a crusher claw,

0:16:10.640 --> 0:16:13.760
<v Speaker 2>and meanwhile the animal regenerates a new claw where the

0:16:13.800 --> 0:16:16.600
<v Speaker 2>old one was torn off. A lot of crustaceans can

0:16:16.640 --> 0:16:19.040
<v Speaker 2>do that. It grows a new claw, and the new

0:16:19.080 --> 0:16:23.720
<v Speaker 2>claw always becomes the cutter claw. But this only happens

0:16:23.720 --> 0:16:25.840
<v Speaker 2>if you do it early. So if you pull off

0:16:25.880 --> 0:16:28.800
<v Speaker 2>a lobster's claw after the larval stage, when it's already

0:16:28.800 --> 0:16:32.440
<v Speaker 2>approaching adulthood, when the asymmetry is already beginning to show up,

0:16:32.960 --> 0:16:36.400
<v Speaker 2>the original arrangement stays intact. The claw you pulled off

0:16:36.440 --> 0:16:46.400
<v Speaker 2>will regenerate as whichever type it already was. So this

0:16:46.760 --> 0:16:50.160
<v Speaker 2>seems to show that claw laterality is determined sometime during

0:16:50.200 --> 0:16:53.320
<v Speaker 2>the molting stages of like four to five, and it

0:16:53.360 --> 0:16:57.200
<v Speaker 2>probably won't change after that, so what causes asymmetry to

0:16:57.200 --> 0:17:01.320
<v Speaker 2>become fixed to during this stage in a young law's life?

0:17:01.440 --> 0:17:05.399
<v Speaker 2>And here begins a long, twisting and to my mind

0:17:05.520 --> 0:17:10.600
<v Speaker 2>fascinating journey of experiments trying to pin down how this happens.

0:17:10.880 --> 0:17:13.360
<v Speaker 2>Most of these experiments Govind himself was in some way

0:17:13.400 --> 0:17:16.360
<v Speaker 2>directly involved in, and for the sake of brevity, I'm

0:17:16.359 --> 0:17:19.199
<v Speaker 2>going to gloss over some details in this section, but

0:17:19.280 --> 0:17:21.240
<v Speaker 2>you can look up the article for yourself if you

0:17:21.240 --> 0:17:24.040
<v Speaker 2>want the more zoomed in version with all the details

0:17:24.080 --> 0:17:28.280
<v Speaker 2>and citations. I'll try to give a more sky level view. So,

0:17:28.359 --> 0:17:30.720
<v Speaker 2>first of all, Govin and colleagues notice some things we

0:17:30.800 --> 0:17:34.320
<v Speaker 2>already know leading into these experiments. One is that the

0:17:34.359 --> 0:17:39.800
<v Speaker 2>triggers for developing different claws must be randomly distributed under

0:17:39.840 --> 0:17:43.720
<v Speaker 2>normal conditions to explain the random distribution of claws in

0:17:43.760 --> 0:17:48.040
<v Speaker 2>the wild, but not random once a claw is lost.

0:17:48.640 --> 0:17:52.560
<v Speaker 2>And this naturally suggested something about use the way the

0:17:52.600 --> 0:17:55.359
<v Speaker 2>claw is used. When one claw is pulled off and

0:17:55.440 --> 0:17:58.399
<v Speaker 2>has to grow back and new, it isn't getting used,

0:17:58.600 --> 0:18:02.160
<v Speaker 2>so the remaining cl law is getting used, and maybe

0:18:02.160 --> 0:18:05.760
<v Speaker 2>it's something about getting used more that makes a claw

0:18:05.880 --> 0:18:09.199
<v Speaker 2>into a crusher. This would align with the fact that

0:18:09.240 --> 0:18:13.240
<v Speaker 2>the juvenile stage in which the claws become asymmetrical also

0:18:13.280 --> 0:18:16.480
<v Speaker 2>coincides with a change in the lobster's lifestyle. So when

0:18:16.480 --> 0:18:19.240
<v Speaker 2>the claws start to become asymmetrical is around the time

0:18:19.280 --> 0:18:23.840
<v Speaker 2>when lobsters transition from swimming amongst the plankton to living

0:18:23.960 --> 0:18:27.200
<v Speaker 2>on the ocean floor and crawling around on the substrate

0:18:27.280 --> 0:18:31.639
<v Speaker 2>and burrowing in the substrate substrate meaning the stuff that

0:18:31.720 --> 0:18:35.159
<v Speaker 2>lines the ocean floor. Now, some research had been done

0:18:35.200 --> 0:18:37.800
<v Speaker 2>which found that if you take a bunch of lobsters

0:18:37.840 --> 0:18:42.080
<v Speaker 2>and you raise them in smooth plastic trays environments with

0:18:42.240 --> 0:18:45.560
<v Speaker 2>no stuff to mess with on the bottom of the water,

0:18:46.240 --> 0:18:50.119
<v Speaker 2>lobsters do not, in fact develop crusher claws at all.

0:18:50.480 --> 0:18:55.040
<v Speaker 2>In smooth environments. They just get symmetrically paired cutter claws,

0:18:55.080 --> 0:18:58.240
<v Speaker 2>two cutters exactly the same. But if you put a

0:18:58.280 --> 0:19:01.560
<v Speaker 2>lobster that's already reached the stage where its claws split

0:19:01.600 --> 0:19:05.760
<v Speaker 2>into different types into a smooth environment, it keeps its

0:19:05.840 --> 0:19:08.720
<v Speaker 2>crusher claw, So again it gets fixed sometime early on.

0:19:09.200 --> 0:19:11.040
<v Speaker 1>All right, So it seems like it's the environment that

0:19:11.119 --> 0:19:12.320
<v Speaker 1>is key here, right.

0:19:12.440 --> 0:19:14.720
<v Speaker 2>It seems to be something about the texture of the

0:19:14.880 --> 0:19:19.120
<v Speaker 2>environment at the right stage that causes crusher claws to emerge.

0:19:19.480 --> 0:19:22.719
<v Speaker 2>So here's a new experiment. You raise lobsters in a

0:19:22.720 --> 0:19:26.879
<v Speaker 2>smooth plastic environment versus one scattered with pieces of broken

0:19:26.960 --> 0:19:30.800
<v Speaker 2>oyster shells? Does a lobster grow up differently with different

0:19:30.800 --> 0:19:35.040
<v Speaker 2>distributions of claws on smooth plastic versus oyster chips? And

0:19:35.080 --> 0:19:39.119
<v Speaker 2>the results were oyster shells give you normal asymmetrical lobsters

0:19:39.160 --> 0:19:42.919
<v Speaker 2>with a crusher and a cutter. The smooth, no substrate

0:19:43.040 --> 0:19:47.480
<v Speaker 2>gives you a pair of identical cutters. This was fascinating

0:19:47.480 --> 0:19:50.120
<v Speaker 2>to me. Okay, so it's like what it's crawling around

0:19:50.240 --> 0:19:54.840
<v Speaker 2>on determines how its claws develop. So they wanted to

0:19:54.880 --> 0:19:58.479
<v Speaker 2>refine this answer further. Why is this it? Is this

0:19:58.560 --> 0:20:01.720
<v Speaker 2>result something about oyster chips in particular, or could it

0:20:01.800 --> 0:20:05.280
<v Speaker 2>be any substrate. So they tried the experiment again, but

0:20:05.359 --> 0:20:08.920
<v Speaker 2>instead of oyster shells, they used different stuff. They used gravel,

0:20:09.200 --> 0:20:12.880
<v Speaker 2>they used mud with debris, and they even used tanks

0:20:12.920 --> 0:20:17.479
<v Speaker 2>with plastic shirt buttons and all of these produced normal

0:20:17.560 --> 0:20:22.560
<v Speaker 2>lobsters with one crusher, one cutter normally randomly distributed crusher claws,

0:20:23.080 --> 0:20:26.399
<v Speaker 2>and in a control they had a flat smooth substrate

0:20:26.720 --> 0:20:30.720
<v Speaker 2>that had been painted to look like oyster chips, but

0:20:30.840 --> 0:20:33.520
<v Speaker 2>it did not but did not have any actual stuff

0:20:33.560 --> 0:20:36.199
<v Speaker 2>to crawl or burrow around in, and this did not

0:20:36.359 --> 0:20:39.080
<v Speaker 2>facilitate differentiation. So on the one that was flat and

0:20:39.119 --> 0:20:44.600
<v Speaker 2>smooth but painted, it still produced identical symmetrical cutters. Another

0:20:44.680 --> 0:20:48.520
<v Speaker 2>experiment to refine this what about lobsters in smooth plastic trays,

0:20:48.600 --> 0:20:52.800
<v Speaker 2>but putting them together instead of by themselves. This plays

0:20:52.800 --> 0:20:54.840
<v Speaker 2>on the fact that lobsters are not very friendly to

0:20:54.960 --> 0:20:58.280
<v Speaker 2>each other. They are aggressive and tend to fight each other,

0:20:58.840 --> 0:21:01.720
<v Speaker 2>and typically when they were put in together, they would

0:21:01.880 --> 0:21:04.399
<v Speaker 2>duel a bit and one of the lobsters would often

0:21:04.400 --> 0:21:08.199
<v Speaker 2>get one or both claws removed in battle. Yeah, I know,

0:21:08.280 --> 0:21:11.439
<v Speaker 2>this is kind of going into bug fights territory, but

0:21:11.480 --> 0:21:13.840
<v Speaker 2>the lobster. So what they found was the lobster with

0:21:13.840 --> 0:21:16.800
<v Speaker 2>both claws left would split like in the wild with

0:21:16.840 --> 0:21:21.040
<v Speaker 2>an asymmetrical distribution with one crusher claw. So if there

0:21:21.119 --> 0:21:23.560
<v Speaker 2>is no substrate, if you don't have any mud or

0:21:23.600 --> 0:21:26.720
<v Speaker 2>oyster chips to root around and fighting will also do

0:21:27.119 --> 0:21:29.240
<v Speaker 2>to split your claws into different types.

0:21:29.720 --> 0:21:32.480
<v Speaker 1>Okay, that this makes sense. It's about having It would

0:21:32.480 --> 0:21:34.639
<v Speaker 1>seem to have something to do with the sorts of

0:21:35.080 --> 0:21:39.320
<v Speaker 1>things you're encountering with your claws, be it chunks of

0:21:39.359 --> 0:21:43.560
<v Speaker 1>oysters or the hard body of another lobster combatant.

0:21:43.840 --> 0:21:45.879
<v Speaker 2>Right, it seems to have something to do with doing

0:21:46.040 --> 0:21:50.400
<v Speaker 2>something with the claws that produces one crusher of the two.

0:21:51.080 --> 0:21:53.240
<v Speaker 2>Oh and as a control I thought this is also interesting.

0:21:53.280 --> 0:21:54.720
<v Speaker 2>They're like, well, we want to make sure it's not

0:21:54.800 --> 0:21:58.120
<v Speaker 2>just the appearance of another lobster that causes a crusher

0:21:58.160 --> 0:22:01.120
<v Speaker 2>to develop. So they tried one with a smooth container

0:22:01.160 --> 0:22:04.080
<v Speaker 2>but a mirror, so that if the lobster could see

0:22:04.119 --> 0:22:07.040
<v Speaker 2>its reflection, would this make a differentiate But nope, heerio,

0:22:07.040 --> 0:22:08.160
<v Speaker 2>you just got two cutters.

0:22:08.280 --> 0:22:10.119
<v Speaker 1>It's got to be the tactile experience.

0:22:10.200 --> 0:22:13.359
<v Speaker 2>Okay, yeah, so so far this is all lining up

0:22:13.359 --> 0:22:16.639
<v Speaker 2>with the hypothesis that it's something about the claw getting

0:22:16.840 --> 0:22:19.199
<v Speaker 2>used more that caused them to split and one to

0:22:19.200 --> 0:22:22.679
<v Speaker 2>become a crusher. So they tried a new experiment with

0:22:22.720 --> 0:22:25.040
<v Speaker 2>the hypothesis that if you put a lobster in a

0:22:25.080 --> 0:22:29.400
<v Speaker 2>normal environment with a substrate, but you prevent only one

0:22:29.440 --> 0:22:32.679
<v Speaker 2>of a lobster's claws from opening and closing, that's going

0:22:32.760 --> 0:22:34.879
<v Speaker 2>to get less use. That's going to turn into the

0:22:34.920 --> 0:22:38.479
<v Speaker 2>cutter claw and the other one will become a crusher. Okay,

0:22:38.800 --> 0:22:41.720
<v Speaker 2>So they tried this with various methods, such as holding

0:22:41.760 --> 0:22:43.960
<v Speaker 2>one claw shut with a rubber band or with a

0:22:44.040 --> 0:22:47.840
<v Speaker 2>dab of glue, and they found, to their surprise, this

0:22:48.000 --> 0:22:51.320
<v Speaker 2>did not produce the result they expected. They thought, if

0:22:51.320 --> 0:22:54.080
<v Speaker 2>a claw can't open and close, that the other one's

0:22:54.119 --> 0:22:56.760
<v Speaker 2>going to become the crusher. But no, Instead, with these lobsters,

0:22:57.000 --> 0:23:00.280
<v Speaker 2>you still got random lateralization. In some the right became

0:23:00.320 --> 0:23:02.960
<v Speaker 2>a crusher and some of the left became a crusher. Wow.

0:23:03.040 --> 0:23:05.800
<v Speaker 1>So it because that was going to be my guess

0:23:05.800 --> 0:23:09.359
<v Speaker 1>that it depends on how that particular claw is being used,

0:23:10.240 --> 0:23:15.040
<v Speaker 1>But we see this random distribution occurring even when that

0:23:15.160 --> 0:23:18.359
<v Speaker 1>one claw is, say, rubber banded shut right.

0:23:18.640 --> 0:23:21.399
<v Speaker 2>So here they were like, well, maybe it has something

0:23:21.400 --> 0:23:23.719
<v Speaker 2>to do with the claw being used, but not with

0:23:23.800 --> 0:23:26.360
<v Speaker 2>it being able to open and close, and maybe it's

0:23:26.400 --> 0:23:29.720
<v Speaker 2>something else. So from here they proceeded to a number

0:23:29.760 --> 0:23:33.400
<v Speaker 2>of different anatomical experiments and to try to quickly summarize

0:23:33.400 --> 0:23:35.960
<v Speaker 2>their findings. First of all, they found if you cut

0:23:35.960 --> 0:23:38.960
<v Speaker 2>a tendon, preventing only one of a lobster's claws from

0:23:39.000 --> 0:23:42.680
<v Speaker 2>opening or closing. This does stop it from becoming a crusher,

0:23:43.440 --> 0:23:47.280
<v Speaker 2>possibly by preventing fast muscle fibers from transforming into slow

0:23:47.359 --> 0:23:50.920
<v Speaker 2>muscle fibers. And they reason from this maybe it could

0:23:50.920 --> 0:23:55.240
<v Speaker 2>be a result of severing reflexive nerve pathways in the process.

0:23:55.760 --> 0:23:58.080
<v Speaker 2>So they tried to see what happened if you sever

0:23:58.200 --> 0:24:01.600
<v Speaker 2>a nerve running from the claw to the sort of

0:24:01.600 --> 0:24:05.960
<v Speaker 2>central nervous system control for the claw. A lobster's nervous

0:24:05.960 --> 0:24:08.040
<v Speaker 2>system is not exactly like ours. They don't just have

0:24:08.119 --> 0:24:11.560
<v Speaker 2>one central brain leading out to everything. They've got ganglia,

0:24:11.680 --> 0:24:15.840
<v Speaker 2>you know, the centralized nodes sort of within the nervous system.

0:24:16.160 --> 0:24:18.480
<v Speaker 2>So you would want to be severing the reflexive fiber

0:24:18.600 --> 0:24:22.080
<v Speaker 2>running from the claw to the ganglia. Unfortunately, when they

0:24:22.080 --> 0:24:24.760
<v Speaker 2>did this by severing that nerve somewhere in there, it

0:24:24.960 --> 0:24:28.400
<v Speaker 2>almost always resulted from the lobsters after they came out

0:24:28.400 --> 0:24:32.959
<v Speaker 2>of anesthesia, they would perform what's known as autotomy on themselves,

0:24:32.960 --> 0:24:36.720
<v Speaker 2>So the lobster's nerve is cut, and then the lobster says, okay,

0:24:36.760 --> 0:24:39.600
<v Speaker 2>don't need this claw anymore, and they would sever their

0:24:39.640 --> 0:24:42.879
<v Speaker 2>own arm and grow a new one. This is a

0:24:42.960 --> 0:24:46.280
<v Speaker 2>standard reaction. Actually of crustaceans, when a limb is trapped

0:24:46.359 --> 0:24:48.800
<v Speaker 2>or damaged, they just cut it off and grow a

0:24:48.800 --> 0:24:51.240
<v Speaker 2>new one, which is a fantastic thing to be able

0:24:51.280 --> 0:24:55.639
<v Speaker 2>to do. And apparently severing the nerve within the claw

0:24:55.920 --> 0:24:59.879
<v Speaker 2>seemed to trigger something in the lobster that suggested it

0:25:00.119 --> 0:25:04.040
<v Speaker 2>needed to do that. That causes the behavior in the lobster.

0:25:04.080 --> 0:25:06.359
<v Speaker 2>It says, something's wrong with this lamb. I'm removing it

0:25:06.400 --> 0:25:07.639
<v Speaker 2>and I'll just get a new one.

0:25:07.880 --> 0:25:10.720
<v Speaker 1>Fun tie in for tomorrow's Weird House Cinema episode.

0:25:10.800 --> 0:25:14.119
<v Speaker 2>Oh brilliant. I didn't even make that connection. Yeah, So

0:25:14.359 --> 0:25:17.959
<v Speaker 2>instead the researchers tried to incapacitate the part of the

0:25:18.000 --> 0:25:22.040
<v Speaker 2>central nervous system leading to the clause, so incapacitating it

0:25:22.080 --> 0:25:25.480
<v Speaker 2>more centrally to the body. This did work as expected.

0:25:25.520 --> 0:25:29.560
<v Speaker 2>It did prevent the claw in question from becoming a crusher.

0:25:30.320 --> 0:25:32.760
<v Speaker 2>So it has it must have something to do with

0:25:33.080 --> 0:25:38.200
<v Speaker 2>nerve inputs from the claw that causes the asymmetry to develop.

0:25:38.800 --> 0:25:43.160
<v Speaker 2>And they tested this with some target exercise regimes. Actually,

0:25:43.480 --> 0:25:45.560
<v Speaker 2>and here I thought this was great. So I just

0:25:45.600 --> 0:25:48.919
<v Speaker 2>wanted to read from the article. So Govind writes quote

0:25:49.400 --> 0:25:53.200
<v Speaker 2>in an inspired moment we thought of enhancing activity by

0:25:53.320 --> 0:25:57.400
<v Speaker 2>exercising one of the paired claws in a substrate free environment.

0:25:57.960 --> 0:26:01.480
<v Speaker 2>The lobster was held and its claw law gently stroked

0:26:01.520 --> 0:26:04.440
<v Speaker 2>with a small paint brush so that the bristles were

0:26:04.520 --> 0:26:08.879
<v Speaker 2>gripped several times during a sixty second session. This regimen

0:26:09.040 --> 0:26:12.200
<v Speaker 2>was repeated three times daily at five hour intervals through

0:26:12.240 --> 0:26:16.879
<v Speaker 2>the entire fourth and fifth stages, the molting stages, that is,

0:26:16.960 --> 0:26:19.840
<v Speaker 2>for about a month. A control group of lobsters was

0:26:19.880 --> 0:26:24.840
<v Speaker 2>reared under identical conditions, including being handled but not exercised.

0:26:25.480 --> 0:26:29.040
<v Speaker 2>While the lobsters in the control group developed paired cutter claws,

0:26:29.440 --> 0:26:35.840
<v Speaker 2>the experimental lobsters developed a crusher on the exercised left side.

0:26:36.000 --> 0:26:38.560
<v Speaker 2>The fact that the only perceived difference between the two

0:26:38.600 --> 0:26:42.520
<v Speaker 2>groups of lobsters was the amount of exercise strengthened our

0:26:42.520 --> 0:26:45.840
<v Speaker 2>belief that some minimal level of reflex activity in the

0:26:45.880 --> 0:26:51.000
<v Speaker 2>claw is probably needed to differentiate a crusher claw. However,

0:26:51.280 --> 0:26:53.560
<v Speaker 2>then they said, okay, what happens if we do the

0:26:53.640 --> 0:26:56.679
<v Speaker 2>exact same thing, but we exercise both claws with the

0:26:56.680 --> 0:27:01.119
<v Speaker 2>paint brush, will this give us two crusher claws, which is,

0:27:01.200 --> 0:27:04.240
<v Speaker 2>by the way, something that we basically never find in nature.

0:27:04.359 --> 0:27:07.280
<v Speaker 2>I think they cite one example of a lobster that

0:27:07.400 --> 0:27:11.080
<v Speaker 2>had two external morphologies looking like crusher claws, but the

0:27:11.240 --> 0:27:14.480
<v Speaker 2>muscles inside did not match. So that pretty much never

0:27:14.520 --> 0:27:17.840
<v Speaker 2>happens in nature, and they found no. In fact, their

0:27:17.880 --> 0:27:21.200
<v Speaker 2>experiment could not produce two crusher claws either. In fact,

0:27:21.720 --> 0:27:24.480
<v Speaker 2>it was not only not able to produce two crusher claws,

0:27:24.480 --> 0:27:27.800
<v Speaker 2>it gave them just the opposite. Whereas tickling only one

0:27:27.840 --> 0:27:30.480
<v Speaker 2>claw with a paint brush and making the claw close

0:27:30.520 --> 0:27:33.800
<v Speaker 2>around the paint brush by reflex that made that the

0:27:33.840 --> 0:27:37.639
<v Speaker 2>crusher boss claw. Tickling both claws but the paint brush

0:27:37.680 --> 0:27:41.600
<v Speaker 2>equally turned the lobster into a symmetrical beast with two

0:27:41.720 --> 0:27:45.520
<v Speaker 2>identical cutter claws only. Huh.

0:27:45.560 --> 0:27:49.240
<v Speaker 1>So, if there are any chefs out there who believe

0:27:49.280 --> 0:27:53.040
<v Speaker 1>that the crusher claw is superior, and they're looking for

0:27:53.119 --> 0:27:58.320
<v Speaker 1>ways to create the pure crusher lobster, it thus far

0:27:58.480 --> 0:28:00.960
<v Speaker 1>seemsossible to pull off.

0:28:01.119 --> 0:28:04.280
<v Speaker 2>It does not seem possible, though, though I will say

0:28:04.280 --> 0:28:06.920
<v Speaker 2>this is an older article, I've not looked into subsequent

0:28:06.920 --> 0:28:09.840
<v Speaker 2>attempts to create two crusher claw lobsters, but I doubt it.

0:28:09.880 --> 0:28:12.000
<v Speaker 2>I don't think you can do that. That's just not

0:28:12.119 --> 0:28:16.240
<v Speaker 2>part of the lobster's destiny, not part of its genetic destiny.

0:28:16.840 --> 0:28:18.439
<v Speaker 2>So a lot of this seems to add up to

0:28:18.480 --> 0:28:23.439
<v Speaker 2>show that it's not just stimulation or use of a

0:28:23.560 --> 0:28:27.040
<v Speaker 2>claw that causes it to become a crusher. But that's

0:28:27.080 --> 0:28:29.240
<v Speaker 2>something that seems to be important, is that it is

0:28:29.560 --> 0:28:35.600
<v Speaker 2>differential use, which is somehow weighed or compared internally by

0:28:35.600 --> 0:28:39.760
<v Speaker 2>the lobster's nervous system or ganglia, and the side that

0:28:39.840 --> 0:28:43.000
<v Speaker 2>gets more use becomes a crusher. So it's not you

0:28:43.040 --> 0:28:46.400
<v Speaker 2>can't exercise both sides and make them two crushers. If

0:28:46.400 --> 0:28:49.920
<v Speaker 2>you do them equally, you get no crushers. You've got

0:28:49.920 --> 0:28:54.200
<v Speaker 2>to get one side getting more stimulation or reflex exercise

0:28:54.320 --> 0:28:58.400
<v Speaker 2>than the other one, which suggests that there is I

0:28:58.400 --> 0:29:01.920
<v Speaker 2>don't know that there is some kind of internal comparison

0:29:02.040 --> 0:29:06.600
<v Speaker 2>module going on in the nervous system. And so Govin concludes,

0:29:06.680 --> 0:29:10.000
<v Speaker 2>quote in nature, as in the laboratory, initial use or

0:29:10.040 --> 0:29:13.400
<v Speaker 2>contact of one claw with a substrate sets in motion

0:29:13.600 --> 0:29:18.000
<v Speaker 2>an increasingly greater activity on that side. The greater neural

0:29:18.080 --> 0:29:21.240
<v Speaker 2>input of that side determines in the central nervous system

0:29:21.440 --> 0:29:24.400
<v Speaker 2>its fate as a crusher, and at the same time

0:29:24.640 --> 0:29:28.840
<v Speaker 2>inhibits the opposite side from ever becoming a crusher, and

0:29:29.000 --> 0:29:31.800
<v Speaker 2>Govin ends up using an analogy of a teeter totter.

0:29:32.320 --> 0:29:35.600
<v Speaker 2>I thought this was funny, actual illustrations of crab claws

0:29:35.680 --> 0:29:39.640
<v Speaker 2>on a playground teeter totter. So he shows, okay, you

0:29:39.640 --> 0:29:41.800
<v Speaker 2>can have a balance where one side is a crusher

0:29:41.840 --> 0:29:44.160
<v Speaker 2>and one's a cutter, and so cutter is up in

0:29:44.160 --> 0:29:47.360
<v Speaker 2>the air, crusher is down. You can have balanced with

0:29:47.800 --> 0:29:50.520
<v Speaker 2>both sides straight. You know, they're both hanging up in

0:29:50.560 --> 0:29:52.840
<v Speaker 2>the air and they're both cutter claws. But if you

0:29:52.960 --> 0:29:56.320
<v Speaker 2>tried to have two crusher claws, something doesn't work there.

0:29:56.360 --> 0:29:58.600
<v Speaker 2>It's like the pole in the middle of the teeter

0:29:58.680 --> 0:30:02.120
<v Speaker 2>totter will break, it won't support it. So whatever the

0:30:02.200 --> 0:30:05.960
<v Speaker 2>exact calculus of experience in the nervous system leading to

0:30:05.960 --> 0:30:08.520
<v Speaker 2>claw development, these experiments seem to make it clear that

0:30:08.680 --> 0:30:12.719
<v Speaker 2>claw asymmetry is a prime example of what Govind calls

0:30:12.800 --> 0:30:18.040
<v Speaker 2>quote experience modulating inherent programs, and this seems to be

0:30:18.080 --> 0:30:21.920
<v Speaker 2>the underlying principle behind much of how any organisms body

0:30:22.160 --> 0:30:25.240
<v Speaker 2>is formed and how it behaves, which kind of cuts

0:30:25.280 --> 0:30:28.840
<v Speaker 2>through a lot of naive all or nothing nature nurture

0:30:28.880 --> 0:30:32.880
<v Speaker 2>reasoning like much of what an animal is is necessarily

0:30:32.920 --> 0:30:37.960
<v Speaker 2>a product of both it's genetically innate materials and programs

0:30:37.960 --> 0:30:40.720
<v Speaker 2>that are the starting sort of the building blocks, and

0:30:40.760 --> 0:30:44.160
<v Speaker 2>then life itself, the experience of living in an environment

0:30:44.240 --> 0:30:48.400
<v Speaker 2>and the experiences that the organism has those determine how

0:30:48.440 --> 0:30:52.400
<v Speaker 2>those innate materials and programs are expressed, leading to vastly

0:30:52.440 --> 0:30:57.360
<v Speaker 2>different outcomes, even completely opposite outcomes, flipping the sides on

0:30:57.400 --> 0:31:01.040
<v Speaker 2>which the crusher claw exists. So in the case of

0:31:01.040 --> 0:31:03.040
<v Speaker 2>a lobster, the metaphor is kind of profound.

0:31:03.080 --> 0:31:03.240
<v Speaker 4>You know.

0:31:03.320 --> 0:31:06.120
<v Speaker 2>It starts with potential for a crusher on the right,

0:31:06.520 --> 0:31:09.200
<v Speaker 2>a crusher on the left, or no crusher at all,

0:31:09.360 --> 0:31:14.400
<v Speaker 2>but probably not two crushers, and then eventually the fixed

0:31:14.440 --> 0:31:18.360
<v Speaker 2>form of its adult body depends on some early experience,

0:31:18.800 --> 0:31:22.160
<v Speaker 2>whether and how it digs around in oyster shell chips

0:31:22.280 --> 0:31:26.640
<v Speaker 2>or even shirt buttons, some early experience, some experience of

0:31:26.760 --> 0:31:29.920
<v Speaker 2>moving one claw more than the other, or getting having

0:31:29.920 --> 0:31:33.560
<v Speaker 2>some kind of sensory input causing reflexes. Maybe something that

0:31:33.720 --> 0:31:38.960
<v Speaker 2>is information fed into the central ganglia through the nerves

0:31:38.960 --> 0:31:42.040
<v Speaker 2>and the claws determines Okay, this claw is getting more

0:31:42.160 --> 0:31:44.400
<v Speaker 2>use than the other one. That's the one that's going

0:31:44.440 --> 0:31:46.360
<v Speaker 2>to be the crusher for the rest of my life.

0:31:46.840 --> 0:31:49.680
<v Speaker 1>Fascinating. Now. I had to look this up real quick

0:31:49.720 --> 0:31:52.040
<v Speaker 1>to see if there was any information about the taste

0:31:52.160 --> 0:31:56.120
<v Speaker 1>debate between these two claws. I did find an article.

0:31:56.160 --> 0:31:58.520
<v Speaker 1>This is a two thousand and eight Associated Press article

0:31:58.840 --> 0:32:02.480
<v Speaker 1>titled the Great Lobster Debate, Claws Versus Tails. As the

0:32:02.520 --> 0:32:06.880
<v Speaker 1>title implies, this is mostly about taste differences between the

0:32:06.880 --> 0:32:10.040
<v Speaker 1>claws of a lobster and the tails of a lobster,

0:32:11.440 --> 0:32:16.000
<v Speaker 1>and it points out that that of the two claws,

0:32:16.200 --> 0:32:19.920
<v Speaker 1>the crusher claw generally is tougher than the pincer claw.

0:32:20.480 --> 0:32:23.200
<v Speaker 1>It doesn't get into the taste differences between the two,

0:32:23.360 --> 0:32:25.640
<v Speaker 1>but it does point out that the tail, on the

0:32:25.640 --> 0:32:29.640
<v Speaker 1>other hand, is meteor and more flavorful, in part due

0:32:29.640 --> 0:32:31.840
<v Speaker 1>to the fact that or in large part due to

0:32:31.880 --> 0:32:34.040
<v Speaker 1>the fact that the tail is used more the tail

0:32:34.080 --> 0:32:37.160
<v Speaker 1>muscle is used more than the claw muscles. And this

0:32:37.880 --> 0:32:41.840
<v Speaker 1>is cited to Brian Beal, a lobster expert and professor

0:32:41.880 --> 0:32:43.040
<v Speaker 1>at the University of Maine.

0:32:43.120 --> 0:32:46.840
<v Speaker 2>How many how many lobsters did he have to eat

0:32:46.880 --> 0:32:47.800
<v Speaker 2>for that experiment?

0:32:49.080 --> 0:32:53.120
<v Speaker 1>But it does make me think that maybe, certainly, if

0:32:53.120 --> 0:32:55.640
<v Speaker 1>you're talking about claw vers's claw. It's probably going to

0:32:55.640 --> 0:32:58.800
<v Speaker 1>be a matter of personal preference, but it could be

0:32:58.840 --> 0:33:03.040
<v Speaker 1>wrong on that. Perhaps lobster are aficionados out there have

0:33:03.120 --> 0:33:06.000
<v Speaker 1>some input on this. Maybe there's one claw they find

0:33:06.000 --> 0:33:08.680
<v Speaker 1>themselves going to before the other. Maybe there are even

0:33:09.560 --> 0:33:11.960
<v Speaker 1>certain dishes where oh, well, you only want to use

0:33:12.040 --> 0:33:14.200
<v Speaker 1>this claw for this dish, and then you want to

0:33:14.280 --> 0:33:18.000
<v Speaker 1>save your pincher or save your crusher for some other dish.

0:33:18.000 --> 0:33:18.440
<v Speaker 1>I don't know.

0:33:18.880 --> 0:33:21.120
<v Speaker 2>Well, wait, which one did you say was the one

0:33:21.160 --> 0:33:23.520
<v Speaker 2>that was usually tougher? Was it the crusher?

0:33:23.720 --> 0:33:26.040
<v Speaker 1>This article says the crusher claw, the larger of the

0:33:26.080 --> 0:33:28.720
<v Speaker 1>two used to crush things generally, is tougher than the

0:33:28.720 --> 0:33:29.640
<v Speaker 1>pincer claw.

0:33:29.880 --> 0:33:32.480
<v Speaker 2>To make sense apart, Yeah, so that the crusher claw

0:33:32.520 --> 0:33:35.400
<v Speaker 2>is the slow muscle fiber and the pincher is the

0:33:35.440 --> 0:33:39.239
<v Speaker 2>fast muscle fiber. And oh, I hesitate to say this

0:33:39.280 --> 0:33:41.479
<v Speaker 2>because they may but they may not be comparable at all.

0:33:41.520 --> 0:33:44.560
<v Speaker 2>I'm not sure how the analogy goes across different you know,

0:33:44.680 --> 0:33:46.960
<v Speaker 2>fi love of animal life, but I mean, if you

0:33:47.000 --> 0:33:50.240
<v Speaker 2>think about a chicken, like the breast meat is generally

0:33:50.280 --> 0:33:52.920
<v Speaker 2>the fast muscle fiber and the dark meat is generally

0:33:52.960 --> 0:33:55.760
<v Speaker 2>the slow muscle fiber, and that translates to different types

0:33:55.800 --> 0:33:59.760
<v Speaker 2>of taste and texture within the meat. Like generally chefs

0:33:59.760 --> 0:34:02.640
<v Speaker 2>would cook dark meat to a higher temperature because it

0:34:02.680 --> 0:34:04.880
<v Speaker 2>has more sort of that needs to render out of

0:34:04.920 --> 0:34:06.440
<v Speaker 2>it to render it tender.

0:34:06.800 --> 0:34:11.279
<v Speaker 1>Yeah, this article indicates that generally speaking, your lobster tail,

0:34:11.480 --> 0:34:15.480
<v Speaker 1>that's what's going to get deep fried or whatever, while

0:34:15.520 --> 0:34:18.200
<v Speaker 1>the claw meat is going to be more tender, and

0:34:18.239 --> 0:34:20.759
<v Speaker 1>that's what's going to go into your lobster rolls and

0:34:20.800 --> 0:34:22.320
<v Speaker 1>your lobster club sandwiches.

0:34:23.840 --> 0:34:25.480
<v Speaker 2>I'm sure there are people who want to fight about

0:34:25.480 --> 0:34:27.359
<v Speaker 2>whether you're supposed to deep fry a lobster or not.

0:34:27.719 --> 0:34:31.279
<v Speaker 2>We're not here to settle that debate. But anyway, I

0:34:31.280 --> 0:34:34.000
<v Speaker 2>found this little research journey fascinating trying to pin down

0:34:34.080 --> 0:34:36.920
<v Speaker 2>how and why this happens in a lobster, and it

0:34:36.920 --> 0:34:39.760
<v Speaker 2>also just seems like somehow rich for metaphor.

0:34:40.200 --> 0:34:43.759
<v Speaker 1>Yeah, yeah, this is fascinating. I don't know that I'd

0:34:43.760 --> 0:34:46.839
<v Speaker 1>really given much thought to this, in part because there

0:34:46.880 --> 0:34:51.880
<v Speaker 1>are certainly clawed crustaceans out there that are more pronounced

0:34:51.960 --> 0:34:54.480
<v Speaker 1>in their asymmetry, and I think we're going to get

0:34:54.520 --> 0:34:56.920
<v Speaker 1>into those more in the third episode in this series.

0:34:57.160 --> 0:35:00.440
<v Speaker 2>Yes, there are some crustaceans, specifically some crowd that take

0:35:00.480 --> 0:35:04.440
<v Speaker 2>claw asymmetry to a ridiculous extreme. That we'll save those

0:35:04.440 --> 0:35:05.080
<v Speaker 2>for next time.

0:35:11.719 --> 0:35:15.480
<v Speaker 1>All right, So sticking to the aquatic world here, I

0:35:15.520 --> 0:35:18.319
<v Speaker 1>thought i'd go in another direction that I imagine a lot

0:35:18.320 --> 0:35:20.960
<v Speaker 1>of people were thinking about as we were talking about asymmetry,

0:35:21.000 --> 0:35:22.960
<v Speaker 1>and particularly in the last episode, you know we were

0:35:22.960 --> 0:35:27.319
<v Speaker 1>talking about the blowhole of the toothed whale migrating up

0:35:27.320 --> 0:35:30.840
<v Speaker 1>to the top of the head. Well, we have to

0:35:30.880 --> 0:35:34.200
<v Speaker 1>talk about the flatfish. There are some eight hundred species

0:35:34.239 --> 0:35:37.600
<v Speaker 1>of flatfish in global waters, and probably one of the

0:35:37.640 --> 0:35:42.040
<v Speaker 1>most famous groups here is the flounder. And if you

0:35:42.080 --> 0:35:44.520
<v Speaker 1>haven't seen a flounder, do look up a picture. The

0:35:44.600 --> 0:35:47.560
<v Speaker 1>pictures are. A picture of a flounder is always amusing

0:35:47.800 --> 0:35:52.640
<v Speaker 1>or unsettling. Basically, what has occurred here is that the

0:35:52.680 --> 0:35:56.920
<v Speaker 1>flatfish's eye left or right, depending on the variety of fish,

0:35:57.239 --> 0:36:00.919
<v Speaker 1>has migrated to one side of its body to facilitate

0:36:01.160 --> 0:36:05.840
<v Speaker 1>a sideways life in which it camouflages itself against the

0:36:05.880 --> 0:36:09.880
<v Speaker 1>ocean floor, like basically living on the floor, kind of

0:36:09.960 --> 0:36:12.800
<v Speaker 1>like array or something would live on the floor. But

0:36:14.040 --> 0:36:19.960
<v Speaker 1>it acquires its flatness by being sideways. Both eyes are

0:36:20.000 --> 0:36:21.759
<v Speaker 1>on the side facing up.

0:36:22.680 --> 0:36:27.120
<v Speaker 2>This looks hilarious, and I think it's different, unless I'm

0:36:27.120 --> 0:36:29.080
<v Speaker 2>forgetting one. I think this is different than any of

0:36:29.120 --> 0:36:32.799
<v Speaker 2>the other asymmetry examples we've talked about before, because I

0:36:32.920 --> 0:36:35.000
<v Speaker 2>think all of the other ones have been cases where

0:36:35.040 --> 0:36:38.920
<v Speaker 2>there is something that's originally symmetrical on both sides of

0:36:38.960 --> 0:36:42.040
<v Speaker 2>the body, and then they develop in different ways, like

0:36:42.160 --> 0:36:45.040
<v Speaker 2>one you know, maybe one hole opens and the other

0:36:45.080 --> 0:36:47.520
<v Speaker 2>one closes, or one claw grows bigger and with a

0:36:47.560 --> 0:36:50.120
<v Speaker 2>different shapes than the other, different muscle fibers or something

0:36:50.160 --> 0:36:52.759
<v Speaker 2>like that. They just develop in different ways or two

0:36:52.760 --> 0:36:55.640
<v Speaker 2>different extents. This is a case of a symmetry where

0:36:55.800 --> 0:36:59.239
<v Speaker 2>something that was originally symmetrical has one of the two

0:36:59.280 --> 0:37:04.480
<v Speaker 2>elements migrate to the opposite side, so they're actually switching

0:37:04.680 --> 0:37:07.080
<v Speaker 2>sides instead of just like one growing bigger than the

0:37:07.080 --> 0:37:07.840
<v Speaker 2>other or something.

0:37:08.440 --> 0:37:08.720
<v Speaker 3>Yeah.

0:37:08.840 --> 0:37:11.960
<v Speaker 1>Yeah, it's it's super weird looking. And one of the

0:37:12.000 --> 0:37:15.080
<v Speaker 1>telling things about these fish is that you can also

0:37:15.239 --> 0:37:19.319
<v Speaker 1>look at larval flounders, for example, and see eyes on

0:37:19.440 --> 0:37:23.359
<v Speaker 1>both sides of the larva's head. So it's only as

0:37:23.400 --> 0:37:26.440
<v Speaker 1>they develop and mature that the eyes move to the

0:37:26.480 --> 0:37:29.880
<v Speaker 1>other side. Also, like with some of the whale examples

0:37:29.920 --> 0:37:32.000
<v Speaker 1>we were looking at, you can look back in the

0:37:32.000 --> 0:37:36.600
<v Speaker 1>fossil record and make out a halfway point in the evolution. Particularly,

0:37:36.640 --> 0:37:39.640
<v Speaker 1>you can look at the fifty million year old fossil

0:37:40.000 --> 0:37:44.279
<v Speaker 1>of Anthistium, which has an eye that has migrated to

0:37:44.400 --> 0:37:46.640
<v Speaker 1>the top of the head, but no farther.

0:37:46.920 --> 0:37:49.680
<v Speaker 2>Oh that's interesting. So it would have like it's evolved

0:37:49.760 --> 0:37:52.040
<v Speaker 2>enough that it has one eye pointing up and another

0:37:52.040 --> 0:37:55.640
<v Speaker 2>one sort of pointing perpendicular to that right right, Okay.

0:37:55.560 --> 0:37:58.040
<v Speaker 1>It has not reached its final form. I guess you

0:37:58.040 --> 0:38:02.440
<v Speaker 1>would say. Was reading an article from two thousand and

0:38:02.440 --> 0:38:06.720
<v Speaker 1>eight in the journal Nature by A. Matt Friedman titled

0:38:06.880 --> 0:38:11.080
<v Speaker 1>the evolutionary origin of flatfish asymmetry, and he points out

0:38:11.160 --> 0:38:17.120
<v Speaker 1>that Eocene fossil evidence here with Amphistium and another species,

0:38:17.360 --> 0:38:21.560
<v Speaker 1>heteronic ties, both demonstrate the intermediate form.

0:38:22.000 --> 0:38:24.880
<v Speaker 2>I mean, I guess isaat right angles is better than

0:38:24.920 --> 0:38:26.440
<v Speaker 2>one eye just looking down in the dirt.

0:38:26.800 --> 0:38:30.719
<v Speaker 1>Yeah, yeah, but it's it's again. This one makes me

0:38:30.719 --> 0:38:32.840
<v Speaker 1>think back to the cock eyed squid. It makes me

0:38:32.880 --> 0:38:36.160
<v Speaker 1>think of just some of the strange challenges of aquatic

0:38:37.160 --> 0:38:41.960
<v Speaker 1>life in general that lead to these adjustments in a

0:38:42.040 --> 0:38:45.960
<v Speaker 1>creature's form. It's so fascinating.

0:38:46.320 --> 0:38:46.520
<v Speaker 2>Yeah.

0:38:46.600 --> 0:38:49.400
<v Speaker 1>Yeah, And of course, well one might ask, well, you know,

0:38:49.400 --> 0:38:51.640
<v Speaker 1>why don't we see more examples of things like this

0:38:52.440 --> 0:38:54.239
<v Speaker 1>in the surface world. And I think the answer to

0:38:54.280 --> 0:38:57.200
<v Speaker 1>that is we do. You know, we talked maybe not

0:38:57.280 --> 0:39:01.279
<v Speaker 1>in so much in terms of asymmetrical solutions, but in

0:39:01.360 --> 0:39:04.360
<v Speaker 1>terms of like eyes moving with the evolution of a

0:39:04.400 --> 0:39:07.799
<v Speaker 1>particular species. I mean, we talked about, we've talked about

0:39:07.800 --> 0:39:10.400
<v Speaker 1>on the show, the difference between the position of eyes

0:39:10.640 --> 0:39:14.440
<v Speaker 1>on a herbivore versus the eyes on a predator. You know,

0:39:14.520 --> 0:39:16.319
<v Speaker 1>do you need your eyes in a position where you

0:39:16.360 --> 0:39:19.480
<v Speaker 1>can basically see all around you as much as possible

0:39:19.520 --> 0:39:21.319
<v Speaker 1>at a given time, or do you need those things

0:39:21.400 --> 0:39:24.040
<v Speaker 1>hyper focused on the thing that's in front of you?

0:39:24.040 --> 0:39:27.920
<v Speaker 1>You know, these are positions that are reached via evolution.

0:39:28.440 --> 0:39:31.319
<v Speaker 2>Yeah, and actually, to take that even further though, this

0:39:31.360 --> 0:39:33.040
<v Speaker 2>has less to do with the placement of the eyes,

0:39:33.040 --> 0:39:36.040
<v Speaker 2>but more about the shapes of the actual eyeballs themselves.

0:39:36.120 --> 0:39:38.680
<v Speaker 2>You know, we talked not too long ago about research

0:39:38.719 --> 0:39:43.760
<v Speaker 2>even finding differences in common eye shapes based on whether

0:39:43.840 --> 0:39:46.880
<v Speaker 2>a predator is like is an active predator or an

0:39:46.880 --> 0:39:50.200
<v Speaker 2>ambush predator you know that tends to specialize for different

0:39:50.280 --> 0:39:52.439
<v Speaker 2>types of vision, Like do you need to have really

0:39:52.440 --> 0:39:58.040
<v Speaker 2>good vision for estimating the distance needed for one pouncing jump,

0:39:58.160 --> 0:40:00.279
<v Speaker 2>or do you need the kind of vision needed for

0:40:00.760 --> 0:40:02.520
<v Speaker 2>chasing over a period of time.

0:40:03.000 --> 0:40:06.000
<v Speaker 1>Yeah, yeah, exactly. So that's a fun example that I

0:40:06.080 --> 0:40:08.279
<v Speaker 1>just had to bring up. But I have another one here,

0:40:08.320 --> 0:40:11.160
<v Speaker 1>and this is another famous example of asymmetry, and this

0:40:11.280 --> 0:40:16.600
<v Speaker 1>time we are dealing with surface species and surface creatures.

0:40:17.040 --> 0:40:19.960
<v Speaker 1>And it's also an interesting example because it's an example

0:40:20.040 --> 0:40:24.680
<v Speaker 1>of a symmetry leading to more asymmetry. What happens when

0:40:24.920 --> 0:40:31.440
<v Speaker 1>an asymmetrical creature is your preferred prey, Perhaps you become

0:40:31.480 --> 0:40:34.239
<v Speaker 1>more asymmetrical in order to take advantage of it.

0:40:34.600 --> 0:40:38.240
<v Speaker 2>Oh that's interesting. So you'd imagine, like I'm just making

0:40:38.239 --> 0:40:40.760
<v Speaker 2>this up, but if you're fighting some kind of giant

0:40:40.800 --> 0:40:43.440
<v Speaker 2>lobster and one of its claws is bigger and more

0:40:43.520 --> 0:40:46.880
<v Speaker 2>dangerous than the other, if over evolutionary time, your species

0:40:46.960 --> 0:40:50.080
<v Speaker 2>develops i don't know, tougher skin or defenses on the

0:40:50.160 --> 0:40:53.800
<v Speaker 2>side that matches the more dangerous lobster.

0:40:53.480 --> 0:40:57.440
<v Speaker 1>Claw, Yeah, assuming there's some consistency in which side of

0:40:56.960 --> 0:40:59.719
<v Speaker 1>the giant lobster of the money claws on.

0:41:00.120 --> 0:41:01.800
<v Speaker 2>That's true. I guess if it was the American lobster

0:41:01.800 --> 0:41:03.959
<v Speaker 2>would be random. So you're just out of luck there.

0:41:04.160 --> 0:41:07.839
<v Speaker 1>Yeah, but in this case we're dealing talking about the food. First,

0:41:07.880 --> 0:41:12.440
<v Speaker 1>we're dealing with snails, and snails are obviously asymmetrical, possessing

0:41:12.480 --> 0:41:18.200
<v Speaker 1>either clockwise or counterclockwise spiraling shells, and as as a

0:41:18.320 --> 0:41:23.920
<v Speaker 1>side note, slugs are also asymmetrical. Slugs, of course, are

0:41:24.160 --> 0:41:28.120
<v Speaker 1>evolutionarily speaking, they are snails that no longer need to

0:41:28.120 --> 0:41:31.080
<v Speaker 1>carry their homes with them, have put that sort of

0:41:31.080 --> 0:41:35.040
<v Speaker 1>lifestyle behind them, but they really retain the asymmetry.

0:41:35.160 --> 0:41:37.880
<v Speaker 2>Wow, I did not know this. So if I understand right,

0:41:37.880 --> 0:41:42.120
<v Speaker 2>you're saying that the slugs evolved from ancestral snails, they

0:41:42.160 --> 0:41:45.320
<v Speaker 2>evolved from creatures that did have shells, and they evolved

0:41:45.320 --> 0:41:48.239
<v Speaker 2>to lose them to internalize them.

0:41:48.360 --> 0:41:51.560
<v Speaker 1>Yeah. We cover this on an old episode of Stuff

0:41:51.560 --> 0:41:53.320
<v Speaker 1>to Blow your Mind many years back, and so some

0:41:53.440 --> 0:41:55.960
<v Speaker 1>of the details are a bit foggy, but yeah, this

0:41:56.040 --> 0:42:00.160
<v Speaker 1>is the basic story of slugs and snails. And by

0:42:00.160 --> 0:42:01.879
<v Speaker 1>the way, if you look at a slug, you can

0:42:01.920 --> 0:42:06.200
<v Speaker 1>still you can visually mark the asymmetry if you look

0:42:06.239 --> 0:42:09.280
<v Speaker 1>for a particular it looks like a little circular feature,

0:42:09.360 --> 0:42:12.799
<v Speaker 1>a little hole or orifice on their body that is

0:42:12.840 --> 0:42:15.640
<v Speaker 1>the Numa stone. And yeah, it's on one side as

0:42:15.640 --> 0:42:16.439
<v Speaker 1>opposed to the other.

0:42:16.760 --> 0:42:19.239
<v Speaker 2>That's really cool because that's another case where it's like,

0:42:20.480 --> 0:42:24.880
<v Speaker 2>I don't know, just imagining evolution operating in a direction

0:42:25.000 --> 0:42:27.799
<v Speaker 2>opposite to what you would have just naively assumed. It's

0:42:27.800 --> 0:42:31.000
<v Speaker 2>like knowing that whales evolved from mammals that used to

0:42:31.000 --> 0:42:34.680
<v Speaker 2>be land walkers, you know, the four quadrupedal land mammals

0:42:35.320 --> 0:42:37.319
<v Speaker 2>spent more and more time and water and eventually became

0:42:37.360 --> 0:42:40.440
<v Speaker 2>fully aquatic. So here these would be not that slugs

0:42:40.480 --> 0:42:43.719
<v Speaker 2>evolved to gain shells, but that snails evolved in some

0:42:43.800 --> 0:42:45.400
<v Speaker 2>cases to lose their shells.

0:42:45.760 --> 0:42:47.919
<v Speaker 1>Yeah. I mean, like we've covered time and time again,

0:42:48.040 --> 0:42:51.160
<v Speaker 1>nature is flexible when it comes to evolution. The card

0:42:51.239 --> 0:42:55.520
<v Speaker 1>is always subject to change. The card will change, and

0:42:56.120 --> 0:43:01.000
<v Speaker 1>it's the species that evolved in sells into a corner

0:43:01.080 --> 0:43:05.880
<v Speaker 1>sometimes that find it the hardest to survive long term.

0:43:06.200 --> 0:43:11.439
<v Speaker 2>Okay, So in modern snails and slugs, you've got this asymmetry,

0:43:11.440 --> 0:43:14.040
<v Speaker 2>You've got some part of their biology having a kind

0:43:14.080 --> 0:43:18.320
<v Speaker 2>of clockwise or counterclockwise component, and this would of course,

0:43:18.400 --> 0:43:22.520
<v Speaker 2>be of relevance to any kind of creature that interacts regularly,

0:43:22.640 --> 0:43:25.000
<v Speaker 2>especially with the snail that's got a hard external part,

0:43:25.040 --> 0:43:27.720
<v Speaker 2>that's got this clockwise or counterclockwise.

0:43:27.000 --> 0:43:29.799
<v Speaker 1>Shell right, and that brings us to a species of

0:43:29.840 --> 0:43:34.800
<v Speaker 1>snake known as Awasaki's snail eater also known as Awasaki's

0:43:34.880 --> 0:43:39.000
<v Speaker 1>slug snake, and these are found in the Yayama Islands

0:43:39.040 --> 0:43:43.560
<v Speaker 1>of Japan, and they specialize in eating snails, and they

0:43:43.600 --> 0:43:49.320
<v Speaker 1>have specialized jaw structures that enable them to prey on clockwise,

0:43:49.360 --> 0:43:53.640
<v Speaker 1>spiraling or dexterraal snails. However, as a result, they have

0:43:53.719 --> 0:44:00.319
<v Speaker 1>a harder time preying on counterclockwise or sinestral snails. Soasically,

0:44:00.320 --> 0:44:03.480
<v Speaker 1>the way this works out is the snake's mandibles have

0:44:03.600 --> 0:44:09.200
<v Speaker 1>evolved for extracting snail bodies from their shells, and this

0:44:09.320 --> 0:44:13.359
<v Speaker 1>evolved independently, apparently in at least three subfamilies, according to

0:44:13.760 --> 0:44:18.279
<v Speaker 1>Hoso and Hori, writing in The Herpetological Review in two

0:44:18.320 --> 0:44:22.480
<v Speaker 1>thousand and six, the snake inserts its mandibles into the

0:44:22.520 --> 0:44:26.799
<v Speaker 1>snail's aperture and moves each mandible forward and back to

0:44:26.880 --> 0:44:30.879
<v Speaker 1>extract the body. And these two individuals Hoso and Horri,

0:44:31.200 --> 0:44:34.560
<v Speaker 1>they've written several papers on the snake. If you look

0:44:34.600 --> 0:44:40.160
<v Speaker 1>up Ilasaki Snail Leader, you'll all often or always find

0:44:40.200 --> 0:44:43.720
<v Speaker 1>these researchers involved, including a two thousand and seven paper

0:44:43.800 --> 0:44:49.800
<v Speaker 1>titled right handed Snakes Convergent evolution of asymmetry for functional specialization.

0:44:50.280 --> 0:44:51.960
<v Speaker 2>This is one where you should look up a picture

0:44:52.000 --> 0:44:54.439
<v Speaker 2>if you can. The one I'm looking at now, Rob

0:44:54.480 --> 0:44:57.600
<v Speaker 2>that you supplied has the snake biting onto the snail shell,

0:44:58.120 --> 0:45:00.880
<v Speaker 2>and it's got its upper jaw position on the outside

0:45:00.880 --> 0:45:03.000
<v Speaker 2>of the shell and its lower jaw. I guess that's

0:45:03.000 --> 0:45:06.919
<v Speaker 2>the mandible reaching in underneath the tube of the shell.

0:45:07.000 --> 0:45:09.440
<v Speaker 2>So the lower jaw is what's getting inside.

0:45:09.880 --> 0:45:12.560
<v Speaker 1>Yeah, yeah, And just looking at the pigure it can

0:45:12.560 --> 0:45:14.759
<v Speaker 1>be kind of hard to work out exactly what's going on.

0:45:14.880 --> 0:45:17.200
<v Speaker 1>So I want to read a quote here from this

0:45:17.320 --> 0:45:20.960
<v Speaker 1>two thousand and seven paper. They right. We found that

0:45:20.960 --> 0:45:25.880
<v Speaker 1>snakes in the subfamily Peritinae, except for non snail eating specialists,

0:45:26.200 --> 0:45:29.320
<v Speaker 1>have more teeth on the right mandible than the left.

0:45:29.719 --> 0:45:35.560
<v Speaker 1>In feeding experiments, a snail eating specialist pere Iwasaki, completed

0:45:35.640 --> 0:45:41.320
<v Speaker 1>extracting a dextraal soft body faster with fewer mandible retractions

0:45:41.520 --> 0:45:45.520
<v Speaker 1>than a sinestral body. The snakes failed in holding and

0:45:45.600 --> 0:45:51.200
<v Speaker 1>dropped sinnestral snails more often owing to behavioral asymmetry when striking.

0:45:51.560 --> 0:45:54.359
<v Speaker 2>Wow, so it's been preying on these snails so long

0:45:54.440 --> 0:45:58.320
<v Speaker 2>that it's specialized for having one side of its mouth

0:45:58.680 --> 0:46:01.280
<v Speaker 2>ready to get at a certain side of the tube

0:46:01.400 --> 0:46:05.160
<v Speaker 2>of the snail's shell. And if it attacks a snail

0:46:05.320 --> 0:46:08.560
<v Speaker 2>of the opposite handedness in its spiral, it's going to

0:46:08.560 --> 0:46:10.000
<v Speaker 2>be at a real disadvantage.

0:46:10.200 --> 0:46:15.120
<v Speaker 1>Exactly. Yeah. So again a fascinating example of asymmetry leading

0:46:15.160 --> 0:46:17.600
<v Speaker 1>to more asymmetry in the food chain.

0:46:17.840 --> 0:46:20.359
<v Speaker 2>I'm so scared that at some point here I've said

0:46:20.400 --> 0:46:22.920
<v Speaker 2>snail when I'm at snake and vice versa. I apology,

0:46:23.560 --> 0:46:25.560
<v Speaker 2>I apology, I apology if I did that.

0:46:26.880 --> 0:46:30.040
<v Speaker 1>So anyway, Yeah, definitely look up images of the snakes,

0:46:30.239 --> 0:46:33.120
<v Speaker 1>especially if you find an image of it actually feeding

0:46:33.360 --> 0:46:36.239
<v Speaker 1>on a snailshell. All right, Well, we're going to go

0:46:36.239 --> 0:46:38.400
<v Speaker 1>ahead and cap this one off right here, but we

0:46:38.440 --> 0:46:40.600
<v Speaker 1>will be back. I think it's going to be the

0:46:40.640 --> 0:46:44.600
<v Speaker 1>episode after next in which we return with part three

0:46:44.800 --> 0:46:47.960
<v Speaker 1>in this series, but there will be more creatures of note.

0:46:47.960 --> 0:46:52.040
<v Speaker 1>There will be more fascinating evolution and adaptation, and the

0:46:52.080 --> 0:46:55.759
<v Speaker 1>crabs will finally arrive on the scene, don't they always Yes,

0:46:55.920 --> 0:46:58.600
<v Speaker 1>there's no stopping them in the meantime, if you would

0:46:58.600 --> 0:47:00.200
<v Speaker 1>like to check out other episodes of Stuff to Blow

0:47:00.239 --> 0:47:04.359
<v Speaker 1>Your Mind, our core episodes publish on Tuesdays and Thursdays.

0:47:05.320 --> 0:47:08.879
<v Speaker 1>You can also enjoy, if you like, our listener Mail

0:47:08.920 --> 0:47:11.640
<v Speaker 1>episodes on Mondays, our short form Artifact or Monster Fact

0:47:11.680 --> 0:47:14.839
<v Speaker 1>episodes on Wednesdays and on Fridays. We set aside most

0:47:14.840 --> 0:47:17.480
<v Speaker 1>serious concerns and just talk about a weird film.

0:47:17.960 --> 0:47:20.919
<v Speaker 2>Huge thanks as always to our excellent audio producer Seth

0:47:21.040 --> 0:47:23.480
<v Speaker 2>Nicholas Johnson. If you would like to get in touch

0:47:23.520 --> 0:47:25.719
<v Speaker 2>with us with feedback on this episode or any other,

0:47:25.800 --> 0:47:27.920
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0:47:27.960 --> 0:47:30.800
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0:47:30.840 --> 0:47:39.279
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0:47:39.840 --> 0:47:42.759
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<v Speaker 1>The lat