Fish living in the deep ocean have evolved highly-sensitive eyes that can see a range of colour hues in the near-darkness.
鈥淚t鈥檚 a big surprise,鈥� says Zuzana Musilova at the University of Basel in Switzerland. 鈥淭hey have more sensitive eyes and can see way better than humans in lower light.鈥�
Musilova and her colleagues collected DNA from 26 species of fish that live more than 200 metres below sea-level. Analysing this DNA, the team found that six species carried additional genes for rod opsin 鈥� the light-sensitive protein that enables the retina鈥檚 rod cells to detect light.
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Vertebrate animals use rod opsin to detect light in dim environments, but most species 鈥� including humans 鈥� only have one rod opsin gene. However, adult silver spiny fins (Diretmus argenteus) 鈥� a flat fish that lives at depths down to 2,000 meters鈥� has 38 of them.
The team translated these genes into proteins in a dish and shone lights of different wavelengths onto them, to see how they鈥檇 respond. They found that that these opsins detect a wide range of colours, and are especially sensitive to green and blue light.
鈥淲e believe they can detect more shades of blue and green than us,鈥� Musilova says.
Musilova says having highly sensitive eyes may be useful for detecting the glowing bioluminescence emitted by many deep-sea creatures.
These bioluminescent lights are mostly blue and green in colour. Being able to tell colours apart could help fish distinguish whether a flash comes a predator or prey, Musilova says.
Science
