There is a lot we don't know about the deep ocean but everyday another piece of the puzzle comes together. One such puzzle is the mystery of the Chilean devil ray, once thought to live just under the surface of ocean to keep warm.
The graceful winged fish actually dives down to staggering depths, at incredible speeds. To say the water down there is cooler would be an understatement-it's downright cold, dropping to below 39.2 degrees Fahrenheit. For a fish that scientists firmly believed dwelled at the surface of warm waters, it can withstand a surprisingly cold environment.
While this finding is surprising for scientists, it is also a much sought-after answer to an old question. Thirty years ago researchers found that Chilean devil rays have retia mirabilia, a cranial net of blood vessels that use countercurrent blood flow to exchange heat. The finding caused many to scratch their heads; why would devil rays need this heating mechanism when all they do is laze just below the surface, basking in the sunlight?
They need it because they don't stay at the surface. Rather, they dive almost 1.24 miles down at speeds around 13.4 miles per hour, discovered a team of scientists at the Woods Hole Oceanographic Institution (WHOI) in Massachusetts.
The team tagged 15 devil rays with tags that transmitted to a satellite to understand how the rays move through the ocean. The rays were tagged for a total of nine months. The tags measured the temperature of the water, the depths to which the rays traveled, and the amount of light available at those depths.
"Data from the tags gives us a three-dimensional view of the movements of these animals, and a window into how they're living in their ocean habitat-where they go, when, and why," says Dr. Simon Thorrold, lead author of the study published in Nature Communications on Tuesday, July 1.
With the new data scientists were able to piece together the movements of the Chilean devil ray, diving behavior, and the newly solved mystery of the retia mirabilia heat adaptation. They found that the rays display two diving behaviors. Often they dive at high speeds and then return to the surface in a total of 60-90 minutes. Other times they dive and then stay approximately 3,280 feet below the surface for up to 11 hours.
What the rays are so busy doing at such dark and cold depths is still unknown, but scientists predict that the rays dive to find and feed on deep-water fish. Yet many of the organisms that lurk in the deep ocean remain mysteries.
These findings not only reveal key information about devil rays, but also offer scientists another mystery to study-that of a connection, barely observed, between the surface and the deep ocean. In the meantime, scientists like Thorrold hope to learn more as the rays face mounting pressure from fishing in the Indian and Pacific Oceans.
