This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: When designing a large underwater robot that could swim silently to avoid startling sea creatures, roboticist Rob Shepherd considered the unusual swimming system of oarfish, the meters-long fish whose ribbon-like dorsal fin moves in waves to propel its body. To learn more, he consulted his colleague Willy Bemis, a retired Cornell ichthyologist.
"He called me and said, 'I'm interested in oarfish,' and I said, 'Me too,'" said Bemis, professor emeritus of ecology and evolutionary biology in the College of Agriculture and Life Sciences. That was the start of a collaboration to study the oarfish's unique dorsal fin rays. Oarfish, giant fish that are rarely spotted by humans, have hundreds of these bone-like skeletal structures, which extend from the back of the oarfish.
The fin rays move in coordinated motion, creating waves along the membrane that connects them, which in turn propels the fish. A new study, published Sept. 30 in the journal Ichthyology and Herpetology, is the first to describe the anatomy and series of muscles that allow each of the oarfish's fin rays to rotate independently in a full circle, like a joystick. Bemis is the paper's senior author, while Shepherd, the John F.
Carr Professor of Mechanical Engineering in the Cornell Duffield College of Engineering, is a co-author. Gabriel Afonso, a former visiting researcher in Bemis' lab and currently a doctoral student at the Virginia Institute of Marine Science, is the paper's first author. The fish—and their fin rays—are not well studied, in part because when they die, they break into segments, making intact specimens rare.
With only two recognized species found in oceans all over the world at depths up to 1,000 feet (305 meters) below the surface, oarfish are huge, with ribbon-like bodies. The largest specimens are estimated to reach up to 8 meters (about 26 feet—making the giant oarfish the longest bony fish alive). Like many marine behemoths, they eat tiny crustaceans.
They hold a vertical posture when they do so, made possible in part by the dorsal fin. "Most fishes with long bodies swim like eels," Bemis said. "They move in a series of undulations, pressing the water back and forth.
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