UV vision helps anemonefish find their friends

Nov. 11 (UPI) -- It's easy to get lost in a coral reef. To locate friends and family, anemonefish evolved the ability to see ultraviolet light.

To better understand how anemonefish navigate the bright, busy world of Great Barrier Reef, scientists at the University of Queensland decided to take a closer look at the visual systems of Amphiprion akindynos, a cousin of the anemonefish species made famous by "Finding Nemo."

"We looked at everything starting with the genes they use to see and what proteins they express, and in combination with anatomical data, predicted what these anemonefish can see," Fabio Cortesi, a researcher at UQ's Queensland Brain Institute, said in a news release. "Proteins involved in detecting light have minute, well-known differences that influence which wavelengths of light they absorb."

Scientists discovered a special structure in the fish's eye responsible for detecting the UV signatures of friends and relatives. They published their analysis of the anemonefish's vision Monday in the journal Scientific Reports.

"In the part of the anemonefish's eye that looks forward, the photoreceptors detect a combination of violet light and ultraviolet light," said QBI researcher Fanny de Busserolles. "They seem to be very good at distinguishing color, and very good at seeing UV -- it looks like they use it a lot."

Because anemonefish live in shallow water, mostly operating near the surface, ultraviolet light is readily available. Anemonefish are named for the sea anemones with which they live in symbiosis. Anemones use ultraviolet light to grow. Additionally, the anemonefish's primary food source, zooplankton, absorbs UV light.

But finding friends and family is perhaps just as important as finding shelter and bits of food. The stripes on anemone fish reflect UV light, which helps the anemonefish and their special photoreceptors identify their peers.

"By contrast, a lot of the bigger fish -- including ones that eat anemonefish -- cannot see UV, so if you want to communicate on the reef over short distances, then UV is a very good way to do this," Cortesi said. "UV is essentially a secret channel that only these little fish can use to talk to each other. They can be as flashy as they want and they won't be seen -- and it might be how Nemo's cousin finds its friends."