Light does not travel very far in the ocean – the average depth of the world’s oceans is approximately 12,000 feet and itÂ is 36,200 feet below sea level at its greatest depth. Sunlight can reach some 3,280 feet below sea level but generally does not extend more than 650 feet.Â Nevertheless, deep-sea fish do have the ability to see, although fishes in the deep ocean were traditionally considered to have simplerÂ vision systems. Now, new research shows that several species of deep-sea fish have highly unique vision systems that allow them to see flashes of light that many organisms naturally produce (“bioluminescence“).
In this study, scientists examined the genes of 101 deep-sea fish that spanned 26 different species and found that they carried more genes for rod opsin than the researchers expected.Â OpsinsÂ are light-sensitive proteins in the retina of the eye that help convert light into an electrochemical signal that the brain can interpret. And, rod opsins are specifically used in environments with stable temperatures and low light. However, where humans only have a single rod opsin gene, the researchers found that a fishÂ that livesÂ at depths greater thanÂ 6,000 feet, theÂ silver spinyfin, has 38 rod opsin genes. Overall, half of the speciesÂ in this studyÂ had more than one opsin gene.
â€śWe believe they can detect more shades of blue and green than us,â€ť MusilovĂˇ says.
These additional genes increase the fishes’ sensitivity to different colored lights, which may be able to help them differentiate whether a bioluminescent flash comes from a predator or prey.
According toÂ co-author Dr. Fabio Cortesi, a postdoctoral researcher at Australia’s Queensland Brain Institute, â€śUnderstanding how these visual systems work, how sensitive they are and how they allow these critters to survive in their extreme environment provides a treasure of knowledge that might be useful for future applications, such as in visual sensor design, camera designs or remote sensing.â€ť