Science

Multi-link catfish skull may hold key to better underwater robots

Multi-link catfish skull may h...
The channel catfish is able to capture and manipulate prey via 17 linkages within its skull
The channel catfish is able to capture and manipulate prey via 17 linkages within its skull
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The channel catfish is able to capture and manipulate prey via 17 linkages within its skull
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The channel catfish is able to capture and manipulate prey via 17 linkages within its skull
Bones of the channel catfish skull (top) and corresponding 17-link mechanism (bottom)
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Bones of the channel catfish skull (top) and corresponding 17-link mechanism (bottom)

Even though they don't have flexible tongues, catfish are still able to rotate captured prey within their mouths. A new understanding of how they're able to do so could ultimately lead to more dextrous underwater robots, or other technological advances.

Led by postdoctoral fellow Aaron M. Olsen, a team at Rhode Island's Brown University started by filming captive channel catfish as they caught and swallowed prey. The scientists used a motion capture technique known as X-ray Reconstruction of Moving Morphology, which allowed them to actually see inside the animals' skulls while they ate.

Whereas humans have just a single moveable jaw bone, it was observed that the catfish have over a dozen. These rigid bones are joined to one another by flexible joints, or links. The channel catfish's skull thus functions as a 17-link mechanism, which can move water (and prey) within the mouth via actions such as opening the front of the mouth, expanding the throat vertically, expanding the middle of the mouth horizontally, and flaring the gill covers either up or out.

Bones of the channel catfish skull (top) and corresponding 17-link mechanism (bottom)
Bones of the channel catfish skull (top) and corresponding 17-link mechanism (bottom)

Depending on which of these actions is used, water can be drawn from the front of the mouth to the back, pulling prey in; it can be pushed from the back of the mouth to the front, moving prey forward; and it can be formed into a "compressive wave," likely used for more precise positioning of prey.

For the most part, the fish stick to using seven main movements. Olsen notes that while humans utilize a similar number of arm movements to reach and grasp objects, underwater robotic fish-mouth-like devices could conceivably do things that mechanical arms could not.

"Underwater autonomous vehicles might have a robotic arm, like our own arm, that works well for manipulating heavier items but would fail to grasp or might crush a floating item," he says. "And they might have a suction device that can suck in or blow out floating items but cannot move and rotate them with high precision. Designing something closer in structure to a fish mouth might have an advantage."

A paper on the research was recently published in the journal Integrative Organismal Biology.

Source: Society for Integrative and Comparative Biology via Newswise

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