Deep-sea crabs have colour vision despite living up to 1000m below the surface, scientists find. Measuring the spectral sensitivities of crabs' retinas, sensitivity peaks were in the blue region of the visible spectrum-
Investigating deep waters off Bahamas, US-based researchers recorded the glow of tiny bioluminescent species using a submersible vehicle.
Descending to sites between 600 and 1000m down, the scientists observed flashes of bioluminescence where plankton collided with boulders and corals.
The team also studied how crustaceans react to this light, and found previously unknown sensitivities to blue and ultra violet wavelengths.
To test how larger species perceive their environment despite the lack of sunlight, the researchers used a specialist suction arm on the submarine to carefully collect crustaceans living at the sites. Of the eight species studied by the team, all were sensitive to blue light and two also reacted to ultra violet (UV) wavelengths.
Telling what food is OK
According to the marine expert, the species with the ability to detect two channels of colour could be using this to tell the difference between the green-glowing, often toxic, corals they live on and the blue-hued plankton they eat.