Seventeen pigments, one extraordinary eye: the mantis shrimp hides light switches that could one day steer living cells

Humans see the world with three kinds of colour pigment. The mantis shrimp carries around thirty — and a team from the University of Liège in Belgium and Humboldt University in Berlin has now examined, one by one, the 17 pigments in the band of its eye devoted to colour vision. Led by Camille Brouillon, Alina Pushkarev and Marjorie Liénard, they found three pigments sensitive to far-red light, reaching 687 nanometres — deep red, at the edge of infrared — and four 'bistable' pigments that flip reversibly between two states with light alone: two switched on by red light and off by blue, two the reverse. It is the first time such switches have been described in an animal using the same light-catching molecule humans use. The study is in Science Advances. Why it matters beyond wonder: red light travels deep into living tissue without damaging it, so a natural switch flipped by red light is exactly the kind of tool scientists want for optogenetics — controlling individual cells with light in future therapies.