Look into my eyes (Image: Roy L. Caldwell)

Mantis shrimp see the world in a way like no other. Their bug-like eyes are equipped with a unique vision system, which discriminates between colours using a method never seen before.

Like many animals, humans have three kinds of photoreceptors in their eyes, each sensitive to a different colour. When we see a colour, our brains determine what it is by comparing how much the three photoreceptors respond.

Unlike human eyes, most mantis shrimp have 12 photoreceptors, and some have 21. Now Justin Marshall of the University of Queensland in Brisbane, Australia, and colleagues have found that the process they use to discriminate colours is also different.


A mantis shrimp’s photoreceptors are arranged in a series of channels that range from red to ultraviolet. It was thought this allowed them to discriminate quite similar colours.

Yellow or orange?

But Marshall and his team were surprised to find that the mantis shrimp are quite bad at telling colours apart. They presented the shrimp with coloured objects, only one of which was associated with a food reward – giving the mantis shrimp an incentive to pick the right one. But the mantis shrimp often failed to discriminate between colours that humans see as distinct, such as dark yellow and light orange.

Marshall says the explanation lies in their eyes. Instead of the brain computing a colour based on the numerical ratio of different colour amounts detected by the photoreceptors, the photoreceptors respond in a particular pattern, which is then sent to the brain. The system seems to allow mantis shrimp to quickly identify basic colours without the need for much brain processing.

As the mantis shrimp scans an object, the image will move between different photoreceptors, each of which will respond differently. It is this sequence of responses, rather than comparisons between the photoreceptors, that the mantis shrimp use to identify colours, Marshall says.

Video: Mantis shrimp eyes in action

The system seems to allow mantis shrimp to quickly identify basic colours without the need for much brain processing. This may be a useful trick given their fast-paced lifestyle, which involves clubbing prey with appendages that can accelerate at up to 23 metres per second – faster than a 0.22-calibre bullet.

Rainbow ray

It’s not yet clear how a mantis shrimp’s brain recognises a colour. “We will look at how a code of neural signals is sent to the brain, to see if it is in fact faster than with other animals and whether it has other advantages,” says Marshall. He also plans to look at how the animals use colour to communicate.

Marshall thinks the discovery could change the way we store optical data on discs. On CDs and DVDs, the red range of the spectrum is used to store information, whereas Blu-ray discs only use the blue end of the spectrum. “Mantis shrimp could inspire a ‘rainbow ray’ disc, where information can be packed into the entire spectrum,” says Marshall. “It would allow a lot more data to be stored in the same amount of space.”

He says mantis shrimp eyes could also improve the design of satellites. There are already similarities, says Marshall. The photoreceptors are arranged in a linear array, “which is exactly how we set up satellites and line-scan cameras.” This strip-like arrangement allows the shrimp to build up a picture of their environment by making a sweeping motion with their eyes. “I tried to convince NASA that they designed satellites wrong and should be using the [mantis shrimp] design for their sensors.”

Journal reference: Science, DOI: 10.1126/science.1245824