Key Takeaways on Rainbow Shrimp Vision

• Rainbow shrimp vision is the most complex of any animal on Earth. Also known as the mantis shrimp, the creature has between 12 and 16 photoreceptors, allowing them to see light in wavelengths ranging from deep ultraviolet to polarized light.
• Although mantis shrimp have more photoreceptor cells in comparison to humans, they actually distinguish fewer colors.
• Rainbow shrimp vision may be used for communication or mating, or navigating their environment and help them see through cloudy waters.

Named for its praying mantis-like forelimbs and shrimp-shaped body, the “mantis” shrimp is a carnivorous marine crustacean painted in rainbow hues and a vibrant tail akin to that of a peacock.

With tubular, domelike eyes, this voracious predator is also credited with the most complex vision of any animal on Earth – but scientists aren’t exactly sure why.

What Is Rainbow Shrimp Vision?

Photoreceptors, rods and cones, are specialized cells on the retina that detect light. Humans typically have three photoreceptor cells, which enable them to see approximately a million colors. Mantis shrimp, by comparison, have between 12 and 16 photoreceptors, allowing them to see light in wavelengths ranging from deep ultraviolet to far red, as well as polarized light, which enables the stomatopods to detect prey more effectively.

“Although mantis shrimp have more photoreceptor cells, scientists have discovered that mantis shrimp can distinguish fewer colors than humans. This reduced color resolution but probably speeds up processing, helping mantis shrimp react with lightning-fast attacks,” explains Jennifer Dreyer, curator of the Virginia Institute of Marine Science invertebrate collection.

For nearly three decades, Dreyer has studied marine invertebrates, which are oceanic animals that lack spines. Researchers like Dreyer believe that the mantis shrimp’s large number of photoreceptors allows visual information to be processed directly within the eyes. This reduces the need for a larger, more energy-demanding brain to handle complex color perception.

The Powerful Mantis Shrimp

Known for its ability to break glass with its powerful club-like appendage, mantis shrimp can strike at speeds up to 60 miles per hour. In 2021, Harvard and Duke University researchers mimicked this powerful punch with a spring-loaded latch mechanism. Still, they couldn’t quite match the invertebrate’s power – the tool reached speeds of about 16 feet per second in the water, while the mantis shrimp clocks in at about 65.

Coastal species can be found in waters as shallow as one foot, while deep-sea species have been recorded down to 5,000 feet. Between these depths, the amount of visible light varies deeply.

Because water absorbs light, sunlight can only reach depths of about 650 feet, also known as the Sunlight Zone. There is no light in the Aphotic Zone below 3,000 feet. Like other deep-sea organisms living in the dark, mantis shrimp in the Aphotic Zone have reduced eyes and limited vision capabilities.

Read More: 6 Unusual Traits of Animal Evolution

Why Is the Mantis Shrimp Vision so Powerful?

While Dreyer says more research is needed to understand why mantis shrimp have such intense vision fully, she notes that researchers at present “have a few ideas.”

“Certain parts of the organism’s body reflect circularly polarized light, so it may be used for communicating or for mating. It may also be useful for navigating their environment or for helping the animals see through cloudy water,” she says. “In fact, they are the only animals known to detect circularly polarized light, which is when the wave component of light rotates in a circular motion.”

How Mantis Shrimp Use Their Vision

One reason may be communication. Male mantis shrimp perform courtship dances for females and display aggressive behaviors toward rival males. In both cases, they showcase colored patches that vary in brightness and hue. This suggests flashing colorful patches may convey communication signals detectable by other mantis shrimp, but not by other organisms.

The mantis shrimp can also detect ultraviolet light, potentially aiding them in locating prey or identifying a potential mate.

“This ability helps them locate food resources because particular objects and organisms reflect or emit UV light differently, revealing distinct visual cues. It also aids in identifying potential mates, as some species of mantis shrimp use UV or polarized light patterns on their bodies for communication and courtship,” says Dreyer.

The mantis shrimp is also known to burrow, creating a haven in the seafloor where it can hide, hunt, or raise their offspring. One species, its scientific name Gonodactylaceus falcatus, produces strong circular body patterns, indicating a role in communication during territorial behavior. The ability to discriminate between these patterns and polarization of light can help to avoid already occupied burrows when seeking refuge.

What Makes Their Eyes Unique?

Making all of these skills possible is the unique makeup of shrimp’s eyes.

“Mantis shrimp have compound eyes on separate stalks that can move independently, letting them scan a wide area of their environment more efficiently. Each eye has trinocular vision, meaning it can independently judge depth and distance by using three distinct visual regions to focus on a single object. This is valuable for a predator,” explains Dreyer.

The top and bottom parts of the shrimp’s eyes are mainly used to detect general shapes and motion, while the middle section has six rows of photoreceptors.

Although the eyes are intricate and not yet fully understood, Dreyer says that the underlying system operates on a surprisingly simple principle, all of which still requires further research.

Read More: The 5 Senses Animals Have That Humans Don’t

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