raptorial appendage
of a “spearer” (part of a
molted skin) showing
the typical form of
this type of stabbing
weapon.
peacock mantis
demonstrating
the effect of a
blow of its
dactylus on a snail
shell—fragments can
be seen drifting
away (arrows).
the shrimp had the fastest strike in the animal
kingdom at that time—up to 23 meters/second
or an unheard-of 45 miles per hour underwater. The force of the blow was recorded at more
than 200 pounds of force—astonishing for an
animal weighing a few ounces.
Unexpectedly, Patek then found something
she calls “the double whammy” of a stomatopod smasher’s strike: a second powerful wave
of energy that hit the target a half millisecond
after the actual impact. What the researchers saw in extreme slow motion was a flash of
light as the raptorial appendage hit the target,
followed by a smoky cloud of vapor. It turns
out that the speed of the appendage moving
through the water creates a cavitation bubble
of vaporized water that collapses and slams
into the target with tremendous force.
Patek subsequently showed that the speed
and force of the mantis strike is made possible
by two anatomical adaptations to the raptorial
appendage, one a latch or “trigger” and the
second a springlike, saddleshaped structure (a
hyperbolic paraboloid) that allows the animal
to store tremendous energy in the smasher
appendage until it is released with lightning
speed. When released from its cocked position, the smasher’s clublike appendage can
accelerate at up to 10,000 times the force of
gravity. Larger smashing species are said to deliver blows comparable to the relative force of a
.22-calibre rifle bullet.
Patek has since found a faster attack mechanism in the jaws of trap-jaw terrestrial ants,
but the underwater record remains with the
stomatopods.
In the first group of mantis shrimps, known
as the “hackers” or “smashers,” the second pair
of maxillipeds (also called thoracopods) are
modified into club-like implements which they
can shoot forward at record speed to strike a
solid structure—perfect for dealing with hard-shelled crustaceans and mollusks. This implement not only allows them to overpower and
stun prey, but to penetrate their defenses.
The other group, the “stabbers” or “
spearers,” have the same pair of maxillipeds modified into lance-shaped implements. They shoot
forwards just like the “clubs” of the “
smashers” but they impale the prey and simultaneously hold it fast—ideal for the capture of fishes
and soft-bodied prey such as octopuses.
The Third dimension
One of the most fascinating things about
mantis shrimps is their eyes, believed to be the
