Mantis Shrimp Eyes Hide Reversible Red Light Switches

Mantis Shrimp Eyes have long looked like over-engineering. A single animal carries roughly thirty light-detecting pigments, while human vision gets by with a far smaller set of receptors. Now scientists have shown that several of those extra pigments do something no animal pigment has been shown to do before: they work like reversible light switches, flipping between two stable states as photons arrive, according to a study published in the journal Science Advances.

The team, drawn from the University of Liège in Belgium and Humboldt University in Berlin, set out to measure seventeen visual opsins from the median band, the specialized central strip of the mantis shrimp eye that handles color vision. Invertebrate opsins are notoriously difficult to produce in the lab, so the researchers combined a new in vitro expression platform developed by molecular biologist Marjorie Liénard with electrophysiology techniques refined in Peter Hegemann’s Berlin laboratory, working alongside collaborators in Germany, the United Kingdom and the United States.

The results redraw the map of the animal’s eye. Most of the proteins turned out to be standard green opsins, similar to the human green pigment. Several were infrared opsins, and the remaining proteins responded to blue and orange light. Crucially, four of the proteins proved bistable: one pair switches on with red light and off with blue, while the other pair runs the pattern in reverse. Paired with the eye’s built-in color filters, these pigments stretch the animal’s sensitivity to about 687 nanometers, and they use the same vitamin A-derived chromophore found in human eyes — the first time such pigments have been described in an animal, the university’s announcement notes.

A different way to see red

The contrast with human vision is mechanical. When a human pigment absorbs a photon, its retinal molecule changes shape and eventually detaches from the opsin, which is why staring at a bright light leaves spots drifting across your vision until the pigment rebuilds itself. In the shrimp’s bistable pigments, the incoming photon resets the molecule directly, so the signaling pathway can keep firing without a separate regeneration step.

The researchers describe the strategy as shifting gears with the light. Under harsh midday sun, when the blue, green and ultraviolet sensors are overwhelmed, the red-sensitive pigments keep collecting information. Toward dawn and dusk, the animal can lean on its green pigments and the bistable blue ones instead. Liénard said the motivation was curiosity about the largest collection of rhodopsins ever found in an invertebrate eye, a puzzle that had lingered for decades because so many proteins coexist inside one complex organ, as Optica reports.

Why medicine researchers are watching

Optogenetics — the technique of steering cell activity with beams of light — is where the discovery could eventually matter most. Unlike the channelrhodopsins borrowed from pond algae, the shrimp’s opsins belong to the G-protein-coupled receptor family, which triggers signaling cascades inside cells. G-protein signaling is implicated in cardiovascular, neurological and inflammatory conditions, and it is the target of a large share of approved medicines. Proteins that can be flipped on with red light and off with blue light could one day serve as precise molecular switches for those pathways, and red light carries a practical edge: it reaches deeper into tissue and damages cells less than blue or ultraviolet.

That future is still some distance off, and the researchers are frank about the caveats. No therapy has been built, and behavioral experiments are still needed to confirm how the animal actually uses each pigment while hunting, signaling or defending territory — difficult work with such aggressive predators. The group is now trying to make the opsins’ signaling more selective and to search for similar proteins in closely related species.

For now, Mantis Shrimp Eyes offer a new class of biological hardware and a reminder that strange eyes repay attention. The same Berlin laboratory that helped decode the shrimp’s vision is co-led by Hegemann, who shared the 2026 Nobel Prize in Medicine. The ocean keeps supplying such hardware, too: a recent deep-sea survey turned up new species off Argentina, and deep-sea worms with suckers earned a new genus. As Liénard said, “Nature still harbours many innovations, which can only be uncovered through an approach combining molecular biology, biochemistry, physiology and sensory ecology.”