Mantis shrimps are well-known for their record-breaking punch, killing their enemies with a strike as hard and as fast as a bullet from a gun. Aside from this, these little animals also hold the world record for having the most complex visual system.
A Closer Look at Mantis Shrimp Eyes
We see objects around us because our eyes contain three photoreceptors - red, green, and blue. Dogs have only two photoreceptors, while birds have four. Invertebrates have additional UV photoreceptors, enhancing their visual ability to distinguish between two similar colors. On the other hand, octopuses do not possess color vision but can detect polarized light.
All these abilities are matchless when compared to mantis shrimp vision. These marine crustaceans have up to 16 photoreceptors and can see UV, visible, and polarized light. They are the only member of the animal kingdom known to recognize polarized light, created when the wave component of light moves in a circular motion. Aside from these, mantis shrimps can also use one eye to perceive depth and move the other eye independently.
Inside the compound eyes of mantis shrimps are tens of thousands of ommatidia or elements containing photoreceptor cells, support cells, and pigment cells. The middle of their eye has six rows of varied ommatidia, known as mid-band.
Each row has a specific function to detect particular wavelengths or polarized light. The first four rows perceive UV light as well as the wavelength that is visible to human eyes. Since each row contains a different receptor in the UV, the mantis shrimps possess perfect UV vision. Meanwhile, the ommatidia of the last two rows are made of precisely located tiny hairs, which might be responsible for their polarization vision.
The overall structure of the mantis shrimp eyes also has extraordinary features. For each eye, three parts can look at the same point in space, making 70% of the eye focus on a narrow strip. Such a mechanism also enables them to perceive depth with just one eye. In creating an image, mantis shrimps constantly move their eyes and scan their environment. Their ability to move each eye independently gives them a large field of view.
Role of a Complex Visual System
Many animals are known for using visual signals, and the complex visual system of mantis shrimps has intrigued scientists. By observing their behavior and morphology, scientists conclude that the visual mechanisms of these crustaceans are also used for communication.
Just like the other male members of the animal kingdom, male mantis shrimps perform courtship dances to attract the attention of the females and display aggression toward other males. In these behaviors, colored patches are shown off with varying reflectance properties across individual mantis shrimp. This observation suggests that the tendency to flash such patches informs the receiver about the behavior of the signal giver.
Marine neuroscientist Justin Marshall studied the visions in various marine species, such as mantis shrimps. His investigations regarding the color vision system of these animals have led to the development of innovative technologies such as satellites and camera sensors.
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