like to learn how to play the lobster we have some here and that's not a joke we really do so come up afterwards and i'll show you how to play a lobster
so actually i started working on what's called the mantis shrimp a few years ago because they make sound this is a recording i made of a mantis shrimp that's found off the coast of california
and while that's an absolutelyfascinating sound it actually turns out to be a very difficult project and while i was struggling to figure out how and why mantis shrimp or stomatopods make sound i started to think about
their appendages and mantis shrimp are called mantis shrimp after the praying mantises which also have a fast feeding appendage
about the extreme stomatopod strike work that i've done in collaboration with wyatt korff and
so mantis shrimp come in two varieties there are spearers and smashers
and this is a spearing mantis shrimp or stomatopod and he lives in the sand and he catches things that go by
so a quick strike like that
you can see it's just a really spectacularextension of the limbs exploding upward to actually just catch a dead piece of shrimp that i had offered it
now the other type of mantis shrimp is the smasher stomatopod and these guys open up
so the smasher raptorial appendage can stab with a point at the end or it can smash with the heel and today i'll talk about the smashing type
of strike and so the first question that came to mind was well how fast does this limb move because it's moving pretty darn fast on that video
and i immediately came upon a problem every single high speed video system in the biology department at berkeley wasn't fast enough
to catch this movement we simply couldn't capture it on video and so this had me stymied for quite a long period of time and then a bbc crew came cruising through the biology department looking for a story
to do about new technologies in biology and so we struck up a deal i said well if you guys rent the high speed video system that could capture these movements you guys can film
that allows you to film at extremely high speeds in low light and low light is a critical issue with filming animals
because if it's too high you fry them so this is a
mantis shrimp there are the eyes up here and there's that raptorial appendage and there's the heel and that thing 's going to swing around and smash the snail and the snail 's wired to a stick so he 's a little bit easier to set up the shot
snail rights activists
this was filmed at five thousand frames per second and i'm playing it back at fifteen and so this is slowed down three hundred and thirty three times
and as you'll notice it's still pretty gosh darn fast slowed down three hundred and thirty three times it's an incredibly powerful movement the whole limb extends out the body flexes backwards
just a spectacularmovement and so what we did is we took a look at these videos and we measured how fast the limb was moving to get back to that original question
for those of you who prefer miles per hour that's over forty five miles per hour in water and this is really darn fast in fact it's so
we were able to add a new point
the extreme animal movementspectrum and mantis shrimp are officially the fastest measured feeding strike of any animal system so
so that was really cool and very unexpected so you might be wondering well how do they do it
and actually this work was done in the nineteen sixties by a famous biologist named malcolm burrows and what he showed in mantis shrimp is that they use what's called a catch mechanism or click mechanism and what this basically consists
is a large muscle that takes a good long time to contract and a latch that prevents anything from moving so the muscle contracts and nothing happens and once the muscle 's contracted completely everything 's stored up the latch flies upward and
you've got the movement and that's basically what's called a power amplification system it takes a long time for the muscle to contract and a very short time for the limb to fly out
and so i thought that this was sort of the end of the story this was how mantis shrimps make these very fast strikes but then i took a trip to
this is serious business
what i saw on every single mantis shrimp limb whether it's a spearer or a smasher is a beautiful saddle shaped structure right on the top surface of the limb
and you can see it right here it just looks like a saddle you'd put on a horse it's a very beautiful structure and it's surrounded by membranous areas and those membranous areas suggested to me that maybe this is some kind of dynamically flexible structure
have to have a spring there needs to be some kind of spring loaded mechanism in order to generate the amount of force that we observe and the speed that we observe and the output of the system
so we thought ok this must be a spring the saddle could very well be a spring and we went back to those high speed videos again
and we could actually visualize the saddle compressing and extending and i'll just do that one more time
bit hard to see it's outlined in yellow the saddle is outlined in yellow you can actually see it extending over the course of the strike and actually hyperextending so we've had very solid evidence showing that that saddle shaped structure
an anticlastic surface and this is very well known to engineers and architects because it's a very strong surface in
it has curves in two directions one curve upward and opposite transverse curve down the other so any kind of perturbation spreads the forces over the surface of
this type of shape so it's very well known to engineers not as well known to biologists it's also known to quite a few
the most famous architects is eduardo catalano who popularized this structure and what's shown here is a saddle shaped roof
that he built that's eighty seven and a half feet spanwise it's two and a half inches thick and supported at two points
and one of the reasons why he designed roofs this way is because it's he found it fascinating that you could build such a strong structure that's made of so few materials and can be supported by so few points and all of these are
the same principles that apply to the saddle shaped spring in stomatopods in biological systems it's important not to have a whole lot of extra material requirements for building it
so very interesting parallels between the biological and the engineering worlds and interestingly this turns out the stomatopod saddle turns out to be the first described biological hyperbolic paraboloid spring that's a bit long but it is sort of interesting
so the next and final question was well how much force does a mantis shrimp produce if they're able to break open snails
and so i wired up what's called a load cell a load cell measures forces and this is actually a piezoelectronic load cell that has a little crystal in it and when this crystal is squeezed the electrical properties change and it which in proportion to the forces that go in
so these animals are wonderfullyaggressive and are really hungry all the time and so all i had to do was actually put a little shrimp paste on the front of the load cell and they'd smash away at it and so this is
of the animal just smashing the heck out of this
were able to get some force measurements out and again we were in for a surprise i purchased a one hundred pound load cell thinking no animal could produce more than one hundred pounds at this size of an animal
time is on the x axis and the force is on the y axis and you can see two peaks and that was what really got me puzzled
the first peak obviously is the limb hitting the load cell but there's a really large second peak half a millisecond later
and i didn't know what that was so now you'd expect a second peak for other reasons but not half a millisecond later again going back to those high speed videos there's a pretty good hint of what might be going on
here 's that same orientation that we saw earlier there's that raptorial appendage there's the heel and it's going to swing around and hit the load cell and what i'd like you to do in this shot is keep your eye on this on the surface of the load cell
as the limb comes
flying through and i hope what you are able to see is actually a flash of light
and so if we just take that one frame what you can actually see there at the end of that yellow arrow is a vapor bubble and what that is is cavitation
and cavitation is an extremelypotent fluid dynamic phenomenon which occurs when you have areas of water moving at extremely different speeds
when this happens it can cause areas of very low pressure which results in the water literally vaporizing
and when that vapor bubble collapses it emits sound light and heat and it's a very destructive process and so here it is in the
so this is a potent
in fluid systems
and just to sort of take it one step further i'm going to show you the mantis shrimp approaching the snail this is taken at twenty thousand frames per second
and i have to give full credit to the bbc cameraman tim green for setting this shot up because i could never have done this in a million years one of the benefits of working with professional cameramen
so really just an amazing image slowed down extremely to extremely slow speeds
and again we can see it in slightly different form there with the bubble forming and collapsing between those two surfaces in fact you might have even seen some cavitation going up the edge of the
so to solve this quandary of the two force peaks what i think was going on is that first impact is actually the limb hitting the load cell and the second impact is actually the collapse of the cavitation bubble and these animals may very well be making use of not only the force
so really fascinating double whammy so to speak from these animals
so one question i often get after this talk so i figured i'd answer it now is well what happens to the animal because obviously if it's breaking snails the poor limb must be disintegrating and indeed it does
is that you have to molt and every three months or so these animals molt and they build a new limb and it's no problem very very convenientsolution to that particular problem
like to end on sort of a wacky note
maybe this is all wacky to folks like you
so the saddles that saddle shaped spring has actually been well known to biologists for a long time not as a spring but as a visual signal
of visual signals on what's really in all species their spring and i think one explanation for this could be going back to the molting phenomenon
so these animals go into a molting period where they're unable to strike their bodies become very soft and they're literallyunable to strike or they'll self destruct this is
for real
and what they do is up until that time period when they can't strike they become really obnoxious and awful and they strike everything in sight it doesn't matter who or what and the second they get into that time point when they can't strike any more
just signal they wave their legs around and it's one of the classic examples in animal behavior of bluffing it's a well established fact of these animals that they actually bluff they can't actually strike but they pretend to
very curious about whether those colored dots in the center of the saddles are conveying some kind of information about their ability to strike or their strike force and something about the time period in the molting cycle
so sort of an interesting strange fact to find a visual structure right in the middle of their spring
so to conclude i mostly want to acknowledge my two collaborators wyatt korff and roy caldwell who worked closely with me on this
and also the millerinstitute for basic research in science which gave me three years of funding to just do science all the time and for that i'm very grateful thank you very much
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