When you live half a mile under the ocean, beyond the reach of sunlight, eyes become a less useful resource.
Now researchers believe that crabs living this far beneath the waves of the Bahamas have adapted to use UV light as their method of sifting between potential food or toxins on the coral-studded seabed.
The team, led by Duke University in North Carolina and Nova Southeastern University in Florida, said they believe that the range of crab species detect shorter wavelengths.
Duke biologist Sonke Johnsen said: ‘Call it color-coding your food.’
Johnsen explained that the animals might be using their ultraviolet and blue-light sensitivity to ‘sort out the likely toxic corals they’re sitting on, which glow blue-green and green, from the plankton they eat, which glow blue.’
The discovery explains what some deep-sea animals use their eyes for and how their sensitivity to light shapes their interactions with their environment.
Tamara Frank, a biologist at Nova Southeastern University, said: ‘Sometimes these discoveries can also lead to novel and useful innovations years later’, such as the the X-ray telescope, which was based on lobster eyes.
Frank, who led the study, has previously shown that certain deep-sea creatures can see ultraviolet wavelengths, despite living at lightless depths.
Experiments to test deep-sea creatures’ sensitivity to light have only been done on animals that live in the water column at these depths. The new study is one of the first to test how bottom-dwelling animals respond to light.
The scientists studied three ocean-bottom sites near the Bahamas.
