The long structures seen in manta rays and their relatives function as an early warning system, rather than a defensive weapon.
With hornlike facial fins and diamond-shape bodies that can stretch nearly 30 feet across, manta rays are among the strangest fish in the sea. Yet these behemoths’ most puzzling feature is a whip-like tail that can measure as long as the rest of the fish’s body.
Why mantas and related rays have such long tails has long been a mystery. The fish do not use their tails to propel through the water or to lash out at potential predators. And although stingray tails have a fearsome reputation for deadly stings, manta tails lack defensive spines entirely.
Instead, these elongated tails may act as fine-tuned antennae, specialized to detect approaching danger. In a paper published on Wednesday in the Proceedings of the Royal Society B: Biological Sciences, a pair of researchers analyzed tails belonging to cownose rays, a smaller relative of manta rays. They discovered that this elongated structure contained specialized organs that help sense underwater stimuli, hinting at how other oceanic rays may use their rear appendages.
“The complexity inside the tail was super surprising,” said Júlia Chaumel, a marine biologist at Harvard University and an author of the paper. “We had no idea that this huge structure had a sensorial function.”
While most stingray species reside near the seafloor, mantas and other rays in the myliobatid order spend most of their time in open water. These fish flap their enlarged, triangle-shaped pectoral fins to fly through the water and migrate over long distances.
According to Matt Ajemian, a researcher at Florida Atlantic University who studies sharks and rays, most stingrays have short, muscular tails that they use to flex venomous barbs. But myliobatid rays possess very different backsides.