The mantis shrimp, a small but formidable marine crustacean, possesses a visual system that has long fascinated scientists. Its eyes are often described as among the most complex in the animal kingdom, allowing it to perceive its underwater world in ways vastly different from humans.
The Mantis Shrimp’s Extraordinary Eyes
The mantis shrimp’s visual prowess begins with its unique eye structure. Unlike human eyes, which are single-lens organs, mantis shrimp have compound eyes, similar to insects, composed of thousands of individual visual units called ommatidia. These eyes are mounted on stalks, enabling them to move independently and providing a wide, panoramic field of view. Each eye can even perceive depth on its own, a concept known as trinocular vision, which provides a distinct advantage for a predatory animal.
A central feature of the mantis shrimp eye is its specialized midband, a horizontal strip containing six rows of ommatidia. While humans possess three types of photoreceptors for color vision (tuned to red, green, and blue light), mantis shrimp can have up to 16 different types of photoreceptors, with many dedicated to color perception. This anatomical complexity allows them to process a vast amount of visual information.
Can Mantis Shrimp See Infrared Light?
Despite their extraordinary visual range, mantis shrimp do not see infrared (IR) light. The scientific consensus indicates their visual range extends from deep ultraviolet (approximately 300 nanometers) to far-red light (around 720 nanometers). True infrared wavelengths, which typically begin beyond 780 nanometers, are outside the sensitivity of their photoreceptors.
While some popular accounts suggest mantis shrimp can perceive infrared, scientific studies show their visual spectrum ends at the far-red end of the visible light spectrum. The aquatic environment itself plays a role, as water readily absorbs infrared radiation, making it less useful for underwater vision. Therefore, developing infrared vision would offer little ecological advantage in their natural marine habitats.
The Spectrum They Do See
While infrared vision is not part of their repertoire, the types of light mantis shrimp can perceive are truly remarkable. They possess a sophisticated ability to see ultraviolet (UV) light, which is invisible to humans. This UV perception is crucial for various behaviors, such as detecting prey that reflect or absorb UV light, and for communication, as some species have UV-reflective patches on their bodies. Their specialized photoreceptors enable this capability.
Beyond color and UV, mantis shrimp are exceptional in their ability to detect polarized light. Light waves normally vibrate in all directions, but polarized light vibrates in a specific plane. Mantis shrimp can perceive both linear and circular polarized light, a rare trait in the animal kingdom. Linear polarization helps them spot transparent or camouflaged prey, like jellyfish, that are otherwise difficult to discern against the complex underwater background.
Their capacity to see circularly polarized light is even more unusual, with mantis shrimp being one of the few animals known to possess this ability. Some species use patterns of circularly polarized light on their bodies for private communication channels, such as mating displays or territorial warnings, which predators unable to perceive this light cannot easily intercept. This specialized vision allows them to extract information about their environment that remains hidden to most other creatures.
Why Such Complex Vision?
The specialized vision of mantis shrimp is tuned to their ecological niche and predatory lifestyle. Their ability to perceive a wide spectrum of light, including UV and polarized light, provides advantages in their marine habitats. Detecting polarized light, for instance, allows them to identify camouflaged organisms and transparent prey that might be invisible to animals with less sophisticated vision.
This advanced visual system also plays a role in their complex social interactions. Mantis shrimp utilize distinct visual signals, including patterns of polarized light on their bodies, for species recognition, mating displays, and territorial defense. Their rapid visual processing system, supported by a specialized brain region, enables them to make quick decisions for capturing fast-moving prey and avoiding potential threats.