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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Four visual pigments in mantis shrimp can switch between active and inactive states using different colors of light. Two are activated by red light and switched off by blue light; two others are activated by blue light and switched off by orange light. A second photon restores the active retinal configuration, allowing the pigment to cycle without the external regeneration step used by ordinary human visual pigments.
What the 2026 study found
A team led by Camille Brouillon, Alina Pushkarev and Marjorie Liénard analyzed 17 visual opsins from the mantis shrimp’s median band. The inventory included 12 standard green opsins, three opsins classified as infrared, and two blue-orange bistable opsins. Functional measurements identified four bistable visual pigments among this system.
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| Finding | What was reported |
|---|---|
| Visual opsins analyzed | 17 |
| Standard green opsins | 12 |
| Opsins classified as infrared | 3 |
| Blue-orange bistable opsins | 2 |
| Bistable pigments identified | 4 |
| Maximum sensitivity with colored eye filters | 687 nanometers |
The key result is molecular: these pigments do not simply absorb light and wait for a separate cellular recycling process. They can be driven back into their active state by another photon. Marjorie Liénard, a molecular biologist at the University of Liège, described it as the first animal example of such pigments using the same chromophore found in human vision.
How a bistable visual pigment works
Ordinary visual pigments need regeneration
Opsins are light-sensitive proteins. They bind retinal, a vitamin-A-derived chromophore, to form a visual pigment. In the ordinary human visual cycle, absorbing a photon changes retinal’s shape and starts the signal that ultimately becomes vision. The chromophore then separates from the protein and must be chemically regenerated before that pigment can respond normally again.
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A second photon resets the pigment
In a bistable pigment, the light-altered retinal does not have to leave before the pigment can become active again. A second photon restores retinal to the active configuration while it remains associated with the opsin. Camille Brouillon, a biophysicist at Humboldt University Berlin, said this direct reactivation suggests that the visual system can remain continuously operational.
“Bistable” therefore describes a reversible molecular switch with two stable states, not a claim that the animal sees only two colors. The states are the light-sensitive active form and the altered, inactive or less-active form; the incoming wavelength determines which direction the switch moves.
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The four color-controlled switching directions
The pigments fall into two opposing pairs:
| Pigment group | Activating light | Deactivating light | What that means |
|---|---|---|---|
| Pair one | Red | Blue | Red photons turn the pigment on; blue photons turn it off. |
| Pair two | Blue | Orange | Blue photons turn the pigment on; orange photons turn it off. |
Peter Hegemann, professor of biophysics at Humboldt University in Berlin, summarized the arrangement as two pigments activated by red and deactivated by blue, with the other two working in the opposite direction through blue and orange light.
Do mantis shrimp really see red and infrared light?
The findings provide strong evidence that mantis shrimp possess pigments responsive to long-wavelength light, but they do not by themselves prove how the animal experiences those wavelengths as colors or uses them in behavior.
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Colored filters in the eye extend the reported sensitivity of the system to 687 nanometers, a wavelength in the deep-red part of the spectrum. The study also identifies three opsins as infrared opsins, but that label should not be turned into a claim that mantis shrimp have demonstrated human-like infrared vision. Molecular sensitivity, neural processing and behavioral detection are separate questions.
Earlier work provides broader context. A 2014 Science study reported that some stomatopod photoreceptors sample approximately 300–720 nanometers across 12 receptor types. Behavioral tests in that work found surprisingly poor fine discrimination between nearby wavelengths. The authors proposed that mantis shrimp may combine temporal signals with scanning eye movements and color recognition rather than relying on the conventional opponent-color comparisons used to explain much human color vision.
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Why the eye contains so many visual pigments
The large opsin inventory may let different receptor systems operate under different light conditions, but the ecological explanation remains a hypothesis rather than a demonstrated behavior.
- Red-sensitive bistable pigments could continue responding when ultraviolet, blue and green pigments are saturated in bright conditions.
- Green and blue bistable pigments might be useful during dawn, dusk or other low-light transitions.
- Colored optical filters can tune the spectrum reaching a receptor, extending or separating sensitivities without requiring a completely different opsin for every band.
A 2014 Current Biology study showed this principle in ultraviolet receptors: two visual pigments combined with four mycosporine-like amino-acid filters produced six distinct UV receptor types. The filters act as spectral tuning elements, helping explain how a single eye can create many response channels from a smaller set of proteins.
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Mantis-shrimp pigments compared with human cone pigments
| Comparison | Human cone pigments | Mantis-shrimp bistable pigments |
|---|---|---|
| Switching direction | Not arranged as red/blue or blue/orange reversible pairs | Two activated by red and deactivated by blue; two activated by blue and deactivated by orange |
| Regeneration | Retinal is eventually replaced through the visual cycle | A second photon can restore retinal directly in the pigment |
| Spectral reach reported here | Human cone vision does not extend to the study’s 687-nanometer mantis-shrimp system in the same way | Colored filters extend reported sensitivity to 687 nanometers |
| Evidence status | Human visual physiology is behaviorally established | Molecular switching is demonstrated; ecological function is not yet demonstrated |
What the discovery does—and does not—show
The work establishes a biochemical mechanism and a distinctive arrangement of spectral controls. It does not yet show that the pigments help a mantis shrimp locate prey, avoid predators or defend territory. Those claims require behavioral experiments that connect a particular pigment’s state to an animal’s decisions or performance.
It also does not reveal that mantis shrimp combine all 17 opsins into a single high-resolution color image. The earlier behavioral results, including poor fine wavelength discrimination, caution against treating receptor count as a direct measure of color experience.
Could the pigments be used in optogenetics?
In principle, a protein that can be turned on and off with selected wavelengths could be useful for controlling cells with light. The red/blue and blue/orange pairs offer an especially interesting form of bidirectional control, while direct retinal reactivation could reduce dependence on an external regeneration system.
However, no optogenetic application based on these pigments has been developed. The possibility is a future research direction, not an available technology or product. Researchers would still need to determine how the proteins behave in target cells, whether the required retinal chemistry is compatible with those cells, how much light is needed, and whether the switching is fast, stable and safe enough for experiments.
Why this matters
The study adds a new molecular strategy to the already unusual visual system of mantis shrimp: light can both signal through a pigment and reset that pigment for another response. The result broadens the known design space for animal vision, while leaving the most important biological question open—how, if at all, these reversible switches improve what the animal does in its natural environment.
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