THE nocturnal helmeted gecko has become the first vertebrate known to see colours in the dark.
Most creatures, including humans, have eyes that contain two types of light-sensitive cells. In daylight, animals rely mainly on colour-sensing cones that distinguish between light of different wavelengths. At night, when photons are scarce, they rely exclusively on more sensitive rod cells, which are colour-blind.
The only exception to this rule, and the only animal known to see colours at night, was thought to be the elephant hawkmoth (Deilephila elpenor). It has adaptations, which include different facets of its compound eye, to increase the…
