peacock mantis shrimp | 2016-05-25

so, we’ve looked at human eyes, simple eyes, compound eyes, and a variety of specialized and amazing eyes from some fantastic creatures. now let’s focus down on one tremendous creature: the peacock mantis shrimp.

it’s called a shrimp because it kind of looks like one but it is really a stomatopod. it’s called a peacock because of it’s flashy colouration (which changes depending on fertility cycles, tidal cycles, and fluorescence). and it’s called a mantis because it has two raptorial appendages that it look quite a bit like those on a praying mantis. there are many varieties of mantis shrimp but the peacock one is my favourite.

on any mantis shrimp’s head protrude two, stubby, arm-like stems on which rest the most complex eyes in the entirety of creation. each of these eyes are split into three sections: the rhabdom, the mid-band, and the dorsal and ventral hemispheres. the dorsal and ventral hemispheres detect form and motion, the mid-band has 6 lines filled with 16 different types of photoreceptors (compared to the 3 humans have) which detect a dizzying array of colours and filter light in different spectra, and the rhabdom detects different vibrations of light (different spectra and polarization). since their eyes are split into three section, each eye has independent trinocular vision and therefore has depth perception even if it loses one eye stalk entirely.

put all of this together and you have a visual landscape so complex that we can hardly even imagine what mantis shrimp can see.

mantis shrimp are able to swing these eyes around in every direction and each is controlled separately, so they can see everywhere they want at all times. further, since they can see UV and polarized light, they use their eyes for all manner of detection purposes. for example, female mantis shrimp are only fertile during certain tidal phases and, thus, only when the moon is reflecting particular light polarization. so, the males don’t bother mating unless they can see that particular type of light. further, their incredible level of depth perception grants them a high level of accuracy when hunting.

let’s talk a moment about the hunting these guys do. at the front of their 2-8 inch bodies, beneath their mouths and eyes stalks are those two raptorial arms. some mantis shrimp have little barbed spears on the tips of these but the peacock mantis shrimp (as well as a bunch of other mantis shrimp varieties) have rounded clubs on the ends of theirs; this difference splits the mantis shrimp community into ‘spearers’ and ‘smashers’ (frealz… that’s what the sciencetitians say).

when the smashers arms are folded back, they are functioning a little bit like a set of vice grips. on the top of their arms they have a hyperbolic paraboloid (which is what your basic Pringle chip looks like). when that very strong little shape (strong when it’s not made out of delicious potatoes) is squished, it generates a massive amount of potential energy that gets stored across the joints of the arm. so, just like when you release a vice grip and the handle pops out really quickly, when the mantis shrimp releases the ‘latch’ on its arm, the potential energy from the hyperbolic paraboloid sends the club on the end of the arm flying out at such high speeds that they can smash through glass, crabs, bones, and oysters. the speed is so high and the force is so strong that, if a human could do the same thing with his arm, he could throw a baseball into orbit and could punch straight through steel. further, moving something that fast in water creates a cavitation (a void/bubble) that is super-heated to several thousand Kelvin and creates a shock-blast that is also strong enough to break oyster/crab shells. so, even if the mantis shrimp misses, the shock blast will likely kill the creature anyway.

the clubs themselves never break, despite their smashy smashiness, because they are made up of a bouligand structure which turns out to be entirely unique to them and is currently being studied in order to create new, light-weight, explosion-repulsing body armour, new tank armour, and lighter, stronger cars.

so, we have a creature who can see more than we can possibly imagine and uses that vision to choose when to mate, to hide from predators, and to very accurately smash the crap out of its prey.

amazing.

so far on peacock mantis shrimp and so far on eyes month — i hope you liked it.

check out this video for more on the peacock mantis shrimp:
mantis murder shrimp