Eyes of the Mantis Shrimp.

The mantis shrimp is quite a interesting animal with quite the interesting set of eyes. The deep water predator has what is called a "compound eye" which is "made out of  thousands of small units that each detects light independently". Most humans have three types of cells called photoreceptors for detecting red, blue, and green light. However, within a mantis shrimps eyes there are "12 to 16 different  photoreceptors". This allows the mantis shrimp to see more colors but not in a way many would think. The mantis shrimp can detect ultraviolet light with their eyes in conjunction with the normal light spectrum visible to humans. Mantis shrimp react to this ultraviolet light in different ways; for example "they find some short wavelengths of UV so repulsive that they’ll avoid food that’s paired with those wavelengths".  Theories to why the mantis shrimp have ultraviolet vision are that it could do with "aggressive signaling" or it " might help it to process images very quickly without much contribution from its brain". This lack of more complex brain communication could be helpful for such a fast attacking predator. To add to the eyes complexity "The receptors that detect red to violet colours are connected to different nerves than the ones that detect UV, and both streams lead to different parts of the brain". This means that the mantis shrimp developed its over complicated way of sight two times.

Honestly the theory about how ultraviolet light could speed up and minimize brain function is both the most probable and also most interesting. I wonder if the ultraviolet light replaces or only adds to a reflex system like the spinal chord in humans. If it does it could be a twice as effective of a reflex system. Although if the ultraviolet reactions are involuntary than it would be pretty annoying to be a mantis shrimp who wants food under the wrong lighting. All I can say is it would be a really light - meal (pun always intended).

Yong, Ed. "Nature's Most Amazing Eyes Just Got A Bit Weirder." Phenomena. National Geographic |Phenomena, 04 July 2014. Web. 21 June 2017.