Remarkable fish see colour in deep, dark water

The University of Queensland –

Fish living up to 1500 metres below the surface have developed surprisingly diverse vision that could help them determine predator from prey in the dimly-lit depths of their fish-eats-fish world.

An international research team involving University of Queensland scientists believes the deep-sea discovery that fish could see colour in the dark shines new light on the evolution of vision in vertebrates, including humans.

UQ Queensland Brain Institute scientist Dr Fabio Cortesi said vertebrates used two types of photoreceptor cells — rods and cones — in order to see.

“Cones are used in bright-light conditions, while rods are generally used in dim-light.”

Both rods and cones contain light-sensitive proteins called opsins that absorb light at specific wavelengths.

“Colour vision in vertebrates is due to the fact that cones use around four different opsins,” Dr Cortesi said.

“This variety allows sensitivity to a broad range of colours.

“Ninety-nine per cent of all vertebrates have just one opsin protein in their rods, so most are colour-blind in dim-light conditions because they rely only on that single rod opsin.”

Deep sea fish that live at 200 to 1500 meters below the surface tend to be no exception. UQ deep-sea visual ecology specialist Dr Fanny de Busserolles said water at that depth filtered most light out.

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