To swallow food, some sharks shrug their shoulders

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Sharks don't have tongues to move food through their mouths, so instead some use their... shoulders?


So say scientists who used a sophisticated X-ray movie technology to see, for the first time, that bamboo sharks swing their shoulders internally when they eat. By pulling their "shoulder girdle" back, the sharks create the suction needed to draw food through the back of the mouth and further into the digestive tract, said Ariel Camp, a postdoctoral researcher at Brown University and lead author of the research published in Proceedings B, a Royal Society journal.

"They have this long pharynx, and they have to keep food moving down it," Camp said. "We think this is part of a 'hydrodynamic tongue.' Sharks and fishes that don't have a tongue control the motion of fluid within their mouths to manipulate food."

That means bamboo sharks (Chiloscyllium plagiosum) use their shoulders, composed of a U-shaped girdle of cartilage and various attached muscles, for feeding as well as to control the front-most fins for locomotion, wrote Camp and colleagues from Brown, the University of Alaska at Anchorage and the University of Illinois.