Mantis shrimp are marine crustaceans that have incredibly complex eyes and are able to see a wide range of colors that are invisible to humans. Their eyes have up to 16 photoreceptor types, compared to only 3 in human eyes, allowing them to see many more colors. But exactly what colors can these amazing creatures see?
Mantis shrimp eyes contain photoreceptors that are sensitive to ultraviolet, visible, and polarized light. This allows them to see well into the ultraviolet range and also detect light polarization patterns. Their brains process this visual information in a very sophisticated way to enable complex color vision.
Anatomy of Mantis Shrimp Eyes
Mantis shrimp eyes are made up of thousands of ommatidia, each containing a corneal lens, crystalline cone, and rhabdom. The rhabdoms contain the photoreceptor cells that detect different wavelengths of light.
There are two main types of photoreceptors in mantis shrimp eyes:
| Photoreceptor Type | Function |
|---|---|
| Rhabdoms | Contain visual pigments that respond to different wavelengths of light |
| Microvilli | Contain polarized light filters |
The specific visual pigments in the rhabdoms determine the color sensitivity of that photoreceptor. Mantis shrimp rhabdoms contain up to 16 types of visual pigments, compared to just 3 types in human eyes. This is what gives them their unique color vision capabilities.
The microvilli structures act as polarized light filters. By comparing input from photoreceptors with microvilli orientated in different directions, mantis shrimp can detect the polarization of light. This helps them with tasks like signaling to each other with polarized body patterns.
Mantis Shrimp Color Vision
The 16 photoreceptor types in mantis shrimp eyes allow them to see an incredibly diverse range of colors. Their visible spectrum extends from deep ultraviolet through to far red wavelengths.
Some of the key colors and wavelengths mantis shrimp can see include:
– Ultraviolet (300-400 nm wavelengths)
– Violet (400-450 nm)
– Blue (450-495 nm)
– Green (495-570 nm)
– Yellow (570-590 nm)
– Orange (590-620 nm)
– Red (620-750 nm)
Within these broad color bands, their many photoreceptor types allow mantis shrimp to see subtler shades and distinguish colors that would look identical to human eyes.
Researchers have used microspectrophotometry and electrophysiology techniques to study the spectral sensitivity of mantis shrimp photoreceptors. This involves measuring their electrical responses to different wavelengths of light.
From these studies, we know that some mantis shrimp species have 12 color receptors covering ultraviolet to red light, while others have expanded their color vision even further. For example, the peacock mantis shrimp has 16 types of photoreceptors, enabling them to see a huge diversity of colors.
Behavioral Evidence of Color Vision
As well as studying the physiology of mantis shrimp eyes and photoreceptors, researchers have also looked for evidence of their color vision abilities in natural behavior:
– **Mate selection** – Mantis shrimp show preferences for mates with particular body patterns and colors. This suggests an ability to distinguish subtle color differences between individuals.
– **Camouflage** – Some species camouflage themselves with body patterns, effectively blending into their surroundings. They can seemingly detect the diverse colors and patterns of corals and rocks around them.
– **Food detection** – Mantis shrimp spot and hunt down colorful prey items like fish and crustaceans, indicating color vision and discrimination abilities.
– **Signaling** – When communicating with each other, mantis shrimp use polarized light patterns. The ability to generate and perceive these signals requires complex color vision and polarization detection skills.
All of these natural behaviors provide evidence that mantis shrimp make practical use of their unique color perception abilities in their everyday lives. Their color vision is not just a quirk of their eyes, but an important adaptation for tasks like finding a mate, catching prey, and interacting with each other.
Color Vision Theories
Given their amazing color perception abilities, scientists have pondered how mantis shrimp color vision works. How does their visual system process the information from up to 16 photoreceptor types and enable them to discriminate such a diverse range of colors?
There are a few leading theories for mantis shrimp color vision:
– **Multidimensional color vision** – Each photoreceptor type provides one dimension of color information. By combining input from multiple receptor types, mantis shrimp may perceive colors as points in a multidimensional color space.
– **Tetrachromatic theory** – Their color vision may work similarly to other animals, just with additional receptor types. For example, having 4 receptor types coded for hue like human trichromatic vision, but with 12 more for finer discrimination.
– **Color categorization** – Mantis shrimp may classify colors into distinct categories or gradients mapped to certain behaviors or needs, rather than seeing colors as a multidimensional continuum.
– **Unknown mechanisms** – There may be processing of color information in the mantis shrimp brain that is unlike anything seen before in another animal. Their perception of color could therefore be unimaginable to us.
The exact mechanisms mantis shrimp use to process all the visual information from their photoreceptors and experience color remains an area of active research and debate. Unlocking these secrets could provide insights into how color vision works in general, and perhaps even inspire new imaging technologies.
Polarization Vision
In addition to complex color vision, mantis shrimp can also detect polarized light. Their photoreceptors contain structures called microvilli that act as filters to light polarization.
By comparing signals between microvilli oriented in different directions, the mantis shrimp visual system can detect and analyze polarization patterns. This provides extra information about their surroundings and aids many of their behaviors.
Some key functions of polarization vision in mantis shrimp include:
| Function | Description |
|---|---|
| Detecting transparent prey | Some prey like glass prawns are transparent but polarize light passing through their bodies, allowing mantis shrimp to spot them. |
| Enhanced contrast vision | Polarization filters can increase visual contrast and let them pick out shapes and objects. |
| Navigation | Detecting polarized light patterns in the sky assists with orientation and navigation. |
| Covert communication | Specialized body parts generate polarized signals used in secret communication between mantis shrimp. |
By giving them a kind of extra sensory input, polarization vision provides mantis shrimp with useful additional information about their environment. It likely works together with their color vision to enable their super-powered view of the underwater world.
Conclusion
Mantis shrimp have extraordinarily complex visual systems that grant them color vision far exceeding human abilities. With up to 16 types of photoreceptors, they can see an incredible variety of colors from deep ultraviolet to far red, and also detect polarized light. This allows them to use color for vital behaviors like finding mates, communicating with each other, spotting camouflaged prey, and navigating their habitats.
While the exact mechanisms of mantis shrimp color vision are still being researched, its clear their eyes have evolved specialized adaptations for dividing up the spectrum and discriminating subtle chromatic differences. Unlocking the secrets of their unbelievable color perception could reveal valuable insights into how visual systems and color vision work across biology. The super-sighted mantis shrimp surely still has a lot to teach us about seeing color in the animal kingdom.
