Mantis Shrimp Sees the Reef in UV Light with 'Biological Sunscreen'

Mantis shrimp are known for their colorful exoskeletons and unique abilities. Now, scientists have found that the complex eyes of this sea creature are equipped with optics that actually generate ultraviolet (UV) color vision.

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

The researchers found that the mantis shrimp's six UV photoreceptors pick up on different colors within the UV spectrum based on filters made from an ingredient that others animals depend on as built-in biological sunscreen. More specifically, the filters are composed of so-called mycosporine-like amino acids (MAAs), which are commonly found in the skin or exoskeleton of marine organisms, where they absorb damaging UV rays.

"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," said Bok.

Why would a mantis shrimp need such a sophisticated visual system? That's a good question. Mantis shrimp use their eyes to navigate and spot predators. In addition, they exist on the vibrant coral reef and have complex social interactions that may be mediated by visual cues.

In fact, their eyes may sense and respond to complex visual inputs without the need to think very hard about it. This could mean that the mantis shrimp may be able to process visual cues without the need for a big brain.

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

The findings are published in the journal Current Biology.