These Biomemories are posts that once graced my high school's biology club blog, which has fallen into disrepair since I graduated. I hope that the relative length doesn't deter anyone from reading these, because they really are really cool animals. :D
Overview:
What,
you may ask, is a mantis shrimp? It's neither a mantis nor a shrimp,
but might be what you would get if you could make J.K. Rowling-esque
hybrids and pumped in a lot of magic. View at your own peril.
Mantis
shrimp are essentially a true beacon of evolutionary progress. You will
soon see that if a scientist wanted to prove the absolute amazingness
of evolution, this would be the creature to pick. And they're not just
one species, or even a genus: they make up an entire order, if a small
one: Stomatopoda.
They're marine crustaceans, reaching about a foot
in length, usually living and looking for food on the ocean floor,
chilling out in rock formations or tunnels they build in the sea bed.
They diverged from other crustaceans over 400 million years ago during
the Cambrian period, so they are only distantly related to the likes of
shrimp and lobsters. They mostly live in tropical waters, and can be
diurnal, nocturnal, or crepuscular and have an extremely diverse diet,
both of which characteristics depend on the species.
Why Mantis Shrimp?
If
I were to tell you that the mantis shrimp is not just a crustacean, but
a very intelligent crustacean that is long lived (monogamous for up to
20 years) and exhibits complex behavior like ritualized fighting (common
in larger phyla like mammals and reptiles), excellent learning ability
and memory (they can remember the individuals they meet, by sight,
smell, and sound), and several modes of communication (like
fluorescence, smell, sound, and visual cues), you would probably agree
that this is one awesome order.
But wait! There's more!
The same organisms, the same order, that has all of these complex and highly developed characteristics, also
has amazing vision. Mantis shrimp have hyperspectral color vision,
allowing them to see and distinguish anywhere from infrared to visible
to ultraviolet light at once. They are each separated into three bands
(trinocular vision), allowing each eye to see objects from three
different perspectives, giving both of them highly-developed depth
perception. Their eyes, mounted on stalks and capable of moving
independently, can sense up to twelve distinct color channels extending
to UV, can execute both serial and parallel image processing, have up to
10,000 ommatidia (the individual parts of compound eyes) and 16
different photoreceptor types (where as humans have 4), and can
distinguish polarised light (the orientation of the oscillations of the
waves of light).
Before
it was discovered that mantis shrimp could see circular polarized
light, there were only three known modes of sight - black and white,
color, and linearly polarized vision. So mantis shrimp alone occupy a
quarter of the known ways of perceiving light. Mantis shrimp eyes have
special filters that convert circular polarized light into linear
polarized light. To humans, linear polarized light appears as glare; but
for mantis shrimp, the polarized light is used in mating displays. Gonodactylus smithii is
one of two known species that can see circular polarized light,
finishing up all the possibilities (four linear and two polar) for
polarized light and thus is the only known organism to have optimal
polarization vision. There are a couple of theories as to why they
developed these legit eyes, which include improved communications using
the fluorescence we talked about earlier and internal processing of
images within the eye so that the small brain can have some help from
the rest of the nervous system.
If you don't want to read that
awesome paragraph packed with so many cool facts, just know that
stomatopod eyes are largely considered to be the most complex eyes in the animal kingdom.
But wait! There's more!
These same organisms, this same order, that has such complex behavior, intelligence, life-span, and vision also
has some of the coolest weapons on the planet (just remember that these
guys are violent). So mantis shrimp, as you may have guessed or seen in
the pictures, have these claw-type appendages. There are two kinds of
mantis shrimp: spearers and smashers. Spearers have spiny, pointy arms
to skewer, snag, and generally catch and slice prey, while smashers have
clubs that they use to...smash stuff.
The raw data for their punches:
Peak speeds: 23 m/s (75 ft/s) (fastest kick in the world)
Peak accelerations: 10400 g (like a .22 caliber bullet)
Immediate strike force: 1500 N
That's one of the top fastest movements in the animal kingdom, and the fastest feeding strike.
The
punch is so fast and so powerful that it creates a collapsing cavity
between the claw and the victim. When it collapses, it produces
sonoluminescense(a little light and very high temperatures) and an
explosive shock wave. Essentially, with one punch, the prey is hit
twice: once by the original (1500N) punch, and once by the resulting
shock wave, which can often paralyze or even kill small prey.
How do they do it?
Using
a saddle shaped structure (a hyperbolic paraboloid) in their arm
cavities, they can store immense amounts of elastic energy and then
shoot out their arm with tremendous acceleration, speed, and force.
Considerable developments of what we know about stomatopods and the
strike in particular have come from Sheila Patek, Wyatt Korff, and Roy
Caldwell, from Berkeley. According to Science Daily:
"Patek
is currently conducting experiments which show that the blow yields a
tremendous amount of force - well over a hundred times the mantis
shrimp's body weight.
In a short note appearing in Nature, Patek and her colleagues, graduate student Wyatt
Korff and professor of integrative biology Roy Caldwell, report the
record-setting strike and the unusual saddle-shaped spring in the hinge
of the shrimp's striking appendage that makes it all possible.
This
spring is technically a hyperbolic paraboloid, a structure similar to a
Pringles potato chip. Very strong, especially when compressed,
hyperbolic paraboloids have been used by architects to create structures
that don't easily buckle. The nautilus employs this structural element
to build a sturdier shell. In mantis shrimp, however, the saddle-shaped
structure can also function as a spring, the UC Berkeley researchers
found. It stores energy until a quick release propels the shrimp's club
in a shell-crushing blow.
"We know of no other biological example where this saddle-shaped structure is used as a spring," Patek said."
Here's a video of Patek presenting the stomatopod's kick to the TED conference in 2004.
A few key time points:
1:20 - types of mantis shrimp
2:30 - striking speeds
4:55 - kicking mechanism
8:55 - striking force
10:20 - cavitation
13:45 - prevention of claw deterioration
So,
now you know stomatopods. One order's got it all: intelligence, complex
behavior, a long life-span, Superman-like vision, and a spring-loaded
hyper-punch. Evolution for the win.
Image Sources and Cool Links:
The Eyes:
Wired Blog - The Magnificent, Ultra-Violent, Far-Seeing Shrimp from Mars (by Brandon Keim, Image: Justin Marshall)
Wired Blog - Shrimp Eyes May Hold Key to Better Communications (by Brandon Keim, Image: Roy Campbell)
Science Daily - Mantis Shrimp Vision Reveals New Way That Animals Can See
The Claws:
Trek Earth - Mantis Shrimp (Image: Rabani HMA, 2006)
Fluorescence:
UC Berkeley News - Mantis Shrimp Fluoresce to Enhance Signaling in the Dim Ocean Depths
General:
UC Berkeley - Roy's List of Stomatopods for the Aquarium
The Lurker's Guide to Stomatopods - Stomatopod Biology
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