Jul 17, 2019 | Updated: 11:17 AM EDT

Deep Sea Nightmare Fish See in Color Despite Living in the Dark

May 10, 2019 08:07 AM EDT

The Tub-eye Fish, Stylephorus chordatus (IMAGE)
(Photo : Dr. Wen-Sung Chung, University of Queensland, Australia) This species was found to use five different rod opsins within its eyes. The long cylindrical shape of its eyes increases light capture and also enables the fish to move the eyes from a horizontal to a vertical position.

Deep-sea creatures living at a depth of 1,000 feet or 5,000 feet below live in absolute darkness, and in this case, evolution would usually dictate that such creatures do not necessarily need their sense of sight but instead are equipped with a heightened sense of touch or electrical impulses.

An international collaboration of researchers has discovered several species of fish that likely can see in color, even in regions of the ocean that light cannot reach. The results of their work, as published in Journal Science, shows a completely different picture of life in regions of the ocean that has no sunlight, it also shows how different vision can be for creatures living in the deep.

In detail, their findings show an array of eye adaptations that these deep sea creatures have. When the researchers began to analyze the genomes of more than a hundred species, they found 13 which had genes that would, in fact, allow them to perceive in full color. One such particular species is the silver spinyfin. It has a wide variety of genes that points to it being able to pick up many different wavelengths of light.

"This is the first paper that examines a diverse set of fishes and finds how versatile and variable their visual systems can be," said Karen Carleton, co-author of the paper.

Vertebrates use special proteins called opsins, which can absorb light to see. In this case, the scientists are looking for a very particular type of opsin that is used to see in low light. Now they assumed that all of the fish would have one single rod opsin (which means they cannot determine/see color), and it was mostly true but surprisingly 13 species showed otherwise, in fact, the silver spinyfin had 38. These opsins were put to the test via simulations and assessed if they could see wavelengths of lights and a to what degree.

One possible reason that the team came up with as to why color vision developed among these creatures includes food identification.

"If you want to survive down there you need to quickly decide if you are seeing a potential predator or potential prey," Fabio Cortesi, a co-author on the paper.

Whatever the reason may be, one thing is definitely for sure, further work is needed to understand why and how these adaptations develop and how they work in their natural environment which would not be a very easy task.

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