B i of l uo r escent Mant i s Sh r imp
Mantis shrimp, which live in burrows in shallow waters of the tropical
oceans, are amazing creatures. They can shoot out their claws with the
acceleration of a .22-caliber bullet and have the most advanced eyes known
to exist in the animal kingdom. In several species of mantis shrimp, the
males have strongly fluorescent yellow patches on their carapace (the upper
part of the animal’s exoskeleton, or outer shell).
Mantis shrimp can grow to be up to 1 foot (0.3 m) long, and marine
biologists divide them into two groups, depending on how they attack their
prey. Spearers pierce the fish they hunt with their claws. Smashers bludgeon
crabs, snails, and mollusks. Male shrimp lack teeth and cannot immediately
eat the food they catch, so they pass it on to the female. She masticates
(chews) the food and passes it back to the male as an edible paste.
Male mantis shrimp are very territorial. But given their deadly claws,
it is risky for mantis shrimp to fight each other. For this reason, they first
judge the size of the fluorescent patches on a competitor’s chest to decide
whether it is worth challenging him. Large shrimp have large patches, and
small shrimp have small patches. Only when males have similarly sized
patches will they fight for a burrow, which often contains a potential mate.
Otherwise, the mantis shrimp with the smaller fluorescent patch will
always surrender. By painting larger fluorescent patches on smaller males,
scientists in experimental settings have been able to change the ranking of
the smaller males. They have found that a small mantis shrimp with a large
fluorescent patch can rule the roost.
The mantis shrimp is also known for its remarkable eyes. They are
positioned on flexible stalks on the animal’s head to allow the shrimp to
see in many directions.
Mantis shrimp have at least twelve different types of photoreceptors
(a lens and sensory cells) in their eyes. Scientists suspect that the
sophisticated eyes of the predatory mantis shrimp evolved to efficiently
hunt fast-moving fish. The shrimp’s eyes rapidly detect and distinguish
among different-colored prey. The shrimp are not concerned with
recognizing small differences in color. It is more important that they
use their limited brain capacity to identify an edible fish, calculate the
trajectory of that fish in a split second, and capture the prey before the fish
sees the shrimp and swims away.
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