MANTIS MURDER SHRIMP (Slow Motion) - Smarter Every Day 121

Yeah. Hey it's me Destin, welcome back to Smarter Every Day.

So I've seen enough videos on the internet of a mantis shrimp punching to have a good idea of what's going on, but I don't understand it, like at the mechanical level.

So today on Smarter Every Day my sister has volunteered to model three seemingly unrelated objects to help us understand this a little bit better.

But first, let's go to James Cook University and watch one punch in slow motion.

OK where are we going?

• We're gonna We're gonna go to a place called Yorkeys Knob.

• Shut up!

• That's the name of it.

• To get some crabs.

• We're not!

• From Yorkeys Knob.

(Destin) [laughs] I was hoping I could use that.. but... I can't.

• It's true, the place is called Yorkeys Knob.

(Destin) You weren't lying. So Yorkeys Knob, now I have to find crabs.

• That one. That's a good one. Grab that one. Got him?

• Got him.

• There you go. Crabs in test tubes.

(Destin) I have to say, I've never seen that before.

• It works. It'll be cool. So what we'll do is we'll take one of the test tubes with the crab in it, we'll put the test tube down here which will keep the crab there. He'll come out and go.. bang.. hit the crab and smash the test tube.

(Destin) Really? So the mantis shrimp is.. it's a peacock mantis shrimp.

• Yep.

• Look at that joker. It's pretty awesome. Hey don't they see more colors than any other animal?

• Yeah. They've got incredible vision and their eyes are setup in parts of three. So the top bits look in a different part from the middle, which look at a different part from the bottom.

• Kind of like the fovea on our eyes is different from..

• Yeah.

• OK.

• Out we come. Move little crab.

[LOUD CLICK] - Bang!

• It triggered.

• Pull him out.

[bang] [breaking glass]

(Destin) Yeah, that's crazy. So let's back it up and watch again and you'll notice that there's a cavitation bubble generated at the exact point of impact.

OK first of all, a mantis shrimp isn't even a shrimp. It's actually a stomatopod. We call it a shrimp because it kinda looks like it, but we also call it a mantis because it's similar to a preying mantis with its forearms.

They have similar hunting strategies. Dr Seymour says that punch is so fast that it can't be accomplished by muscle movement alone, there has to be something else going on, which brings up Sheila Patek.

Believe it or not, Dr Patek has determined that the shape of this potato chip is the secret to the punch of the mantis shrimp. Seriously.

This shape is called a hyperbolic paraboloid, and if you've ever taken calculus you've seen it. It's basically a saddle shape and they're super strong.

This saddle is located on top of the smasher, and the stomatopod uses his muscles to compress it like a spring and he holds it back with a latch mechanism. He then releases this potential energy and it drives the club forward at a much higher velocity than would be possible with muscle alone.

So the next time you eat one of these remember there's another animal eating with the same shape you are, only he's doing it at the bottom of the ocean and he's got that shape integrated into the top of his arm.

If you've ever played with a vice clamp before, you've seen this type of mechanism. You can slowly clamp down on the tool, which uses a cam-over action to lock it in place, and if you have it set right and squeeze it hard, you store mechanical strain energy.

When you trip the latch the energy's released and the arm flies forward real fast, but think about this. Mantis shrimp use their little clubber to break open shells that are really hard right?

So why does the shell break and the club doesn't?

Let's watch another clip. This is Dr Seymour feeding a crab to the stomatopod except this time there's no test tube.

• It's flicking the.. It's flicking the rock.

Ohhhh!

• Did you get it?

• Dunno, might have.

• Ohhhh I feel for that crab. [laughs]

[bang]

(Destin) Watch again closer and see if you can see the saddle release the energy.

• Look at that.

• Good grief. Snapped it straight in half.

We're talking about serious forces here.

In engineering we take two materials and we combine them together into composites to make them stronger. For example plywood is made of many layers of wood with the fibers oriented in two different directions.

Mantis shrimps however take this to the next level with an organic polymer called chitin.

At the Wyss Institute for Biologically Inspired Engineering at Harvard, they determined that these fibers aren't rotated only in two principal directions like plywood, it's an entire helix, which gives the structure strength in many different directions.

These strands are then bonded together in a mineralized matrix which makes the whole thing an incredibly strong smasher.

But it gets crazier than that. The team put a section of the smasher in a synchrotron so they could analyze the material makeup. A synchrotron! That's like a particle accelerator.

This is crazy science. They bombarded it hundreds of times to understand the density and the local orientation of the crystals in the material, and guess what.

They found that the crystals near the surface were oriented perpendicular to the impact site and that orientation changed as we move away from the impact site.

Basically the material changes composition and strength at different locations on the inside.

The impact surface is incredibly hard, but the internal structure transitions smoothly to allow the distribution of a huge impulse load throughout the rest of that structure so it can punch stuff all day long without breaking.

So instead of a normal composite like plywood, which are identical layers stacked up and glued together, a mantis shrimp club is a variable composite, meaning you can vary the material makeup and the strength orientation wherever you need it.

This is an incredibly smart way to design a system.

In summary, I want you to love the mantis shrimp. I don't want you to love it just because of the mechanics of how it throws the punch. Not because of the chemistry of the variable composition of the crystalline structure.

The optics.. It can see circularly polarized light.

This is an incredible, incredible animal, and I want you to think about it every time you eat a chip like this.

Can you do that for me?

OK I hope you enjoyed learning how mantis shrimp club. It's all about the hyperbolic paraboloid, or as my Cal 3 teacher taught me, hyperbowic pawabawoid.

Anyway, I'm Destin, you're getting Smarter Every Day.

If you're interested in supporting the crazy trips I do, please consider supporting on Audible.

Audible.com/smarter. You can get any audiobook you want.

(I apologize if you're deaf... it makes no sense for you to support via Audible.)

I listened to 20,000 Leagues Under the Sea when I did this series because I wanted to learn more about marine life. Jules Verne nailed it.

20,000 Leagues Under the Sea, audible.com/smarter.

Thank you so much for your support. I'll leave a link in the video description.

I'm Destin, you're getting Smarter Every Day, have a good one.

It's Derek! He video bombed me. [laugh]

(Destin) Ho!

• [laughs] We could bring the lighting down on the chip please.

Perfect. [laughs] That was really dumb.

(Destin) Which is why I think I'm gonna use it.