Using Biological Sunscreen, Mantis Shrimps View Reefs in UV Light

A new research discovered that the compound eyes of the mantis shrimp are fitted with optics that produces ultraviolet color vision.

The mantis shrimp is known to have a complex visual system, the most complex known to science. These marine crustaceans view color in a fundamentally different manner as compared to other animals. Researchers found that the optics on the shrimps' eyes generate UV color vision.

"The mantis shrimp visual system contains six types of photoreceptors functioning completely outside the visual range of humans," said Michael Bok of the University of Maryland Baltimore County. "Surprisingly, they produce their six UV photoreceptors using only two types of visual pigments by pairing one visual pigment with one of four UV filters. The UV filters block certain wavelengths of light from reaching the photoreceptors, chromatically shifting their sensitivity."

The shrimps' six UV photoreceptors select various colors within the UV spectrum, based on the filters that are made from a key ingredient - mycosprine-like amino acids - which is present in the skin or exoskeleton of the organism, where they suck in the damaging UV rays. The researchers discovered that these ingredients play the same role in the mantis shrimps' complex eyes, but for different purpose.

"The effect is akin to putting red-tinted glasses over your eyes that block other wavelengths of light, except this is being done at the photoreceptor cellular level in shrimp," Bok explained.

Researchers are trying to solve the mystery behind this complex visual. These marine crustaceans use the complex eyes to navigate and identify predators and prey on the reef. Apart from this, they are also known to have complex social interactions that are intervened by different visual signals present on the body.

The complex eyes have 16 or more photoreceptors which, researchers say, provide the mantis shrimp with a complex color and polarization visual system without a big brain to process information, meaning eyes might sense and respond to the complex visual input without the need to rethink.

"The way their eyes are built and how visual information is processed in their brains is so fundamentally different [from] humans that it is very difficult to conceptualize what the world actually looks like to them," Bok said.

The finding was documented in Current Biology.