San Diego researchers have discovered that some sharks use their fluorescent glow to communicate with other sharks deep under water, and their research has provided some really cool images to show how it works.
Scientists from Scripps Institution of Oceanography at UC San Diego, working with experts at the American Museum of Natural History, used a custom-built "shark eye" camera to do the research.
"This study provides the first evidence that sharks can see the fluorescence of their own species," said Dimitri Deheyn, a researcher at Scripps and co-author of the study. "It's not just beautiful but has an ecological purpose."
How does it all work?
Well, people and other land animals live in a full-color environment, but fish live in a world that's mostly blue, because water quickly absorbs most of the visible light spectrum the deeper you go. The research team figured out that many fish absorb that remaining blue light, and then re-emit it in neon colors of greens, reds and oranges.
Then researchers were able to take their findings a step further. They designed a camera that could capture that fluorescent light and they were able to capture a hidden universe.
They focused on two catsharks: chain catsharks and swellsharks.
The scientists went on a number of expeditions at Scripps Canyon in San Diego County. They observed swellsharks in their native habitat, about 100-feet underwater. The team stimulated biofluorescence during night dives with high-intensity blue lights in watertight cases.
The research team recorded the activity (which you can't see with the human eye) using the custom-built underwater camera. The camera had different sets of filters.
"The set of filters we used for the shark-eye had similar effects as if using yellow filters to see fluorescence, as commonly done by divers," Deheyn told NBC7. "The shark eye filter set is just more finely tuned to match the data collected from the eye."
The scientists mathematically modeled the images from the camera, and found that the contrast of the patterns on the biofluorescent sharks increases with depth. That suggests the animals cannot only see the light, but are also probably using it to communicate with one another.
"This is one of the first papers on biofluorescence to show this connection, and a big step toward a functional explanation for fluorescence in fishes," said John Sparks, a curator in the American Museum of Natural History's Department of Ichthyology and a co-author on the paper.
The study was recently published in the journal Scientific Reports.