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Fish are animals that live in the water. They are also vertebrates – animals that have a backbone and a spine. They have gills that permit them to take oxygen from the water. But have you ever wondered how vertebrates eat food? Now researchers at Brown University have x-ray video that shows the action in great detail.

Many fish are power eaters. Bass, for example, can eat goldfish in one big swallow. Thomas Roberts is a biology professor at Brown University. He and his co-workers used new tools to record the fish's movements as it ate.

"And those tools were a combination of high speed x-ray videos combined with CT measurements of the bones of the skull in the bass and pressure probe measurements of the pressure in the water during suction feeding."

Thomas Roberts says the muscles in the head are not powerful enough to create that suction. He says they must work together with the body muscles used for swimming. Scientists had suspected this cooperation in the past, but, until now, they had no proof.

"Fish actually have to use this incredible linkages of skull bones to pull power from the body muscles to generate the really rapid motion in the head and generate suction to pull in prey."

The finding is important to understand how not only bass, but some 30,000 species of water vertebrates evolved. Thomas Roberts explains.

"So this tells us that this clever co-opting of swimming muscles to produce a feeding motion maybe was really important for the evolutionary success of bony fishes."

The study was published in the Proceedings of the National Academy of Sciences.

I'm Marsha James.

VOA correspondent Rosanne Skirble reported this story from Washington. Marsha James adapted it for Learning English. Caty Weaver was the editor.

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