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Scenes from The University of Rhode Island

URI researcher awarded $395,000 NSF grant to study sharks and their feeding mechanisms

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KINGSTON, R.I. -- March 23, 2004 -- Although sharks and vacuum cleaners don’t look like they have much in common, they actually do. While some sharks wrap their mouths around their prey and bite down, other sharks suction their meal as it swims by. Suctioning sharks don't have to be as close to their prey as their biting counterparts to be successful because they draw their prey into their mouth.

Suction feeding has evolved multiple times in different lineages during the evolution of sharks and is the primary mechanism of capturing prey in all skates and most rays, which are considered close relatives of the shark. What happened on the evolutionary road that created divergent paths of how sharks capture their prey, we may never know.

However, University of Rhode Island researcher Cheryl Wilga of North Kingstown, assistant professor of biological sciences, will attempt to shed some light on how sharks bite or suction by studying their jaws and their feeding mechanisms, thanks to a recently awarded, three-year $395,000 National Science Foundation grant.

Wilga has always been fascinated in how things work, particularly sharks. She is, in biological lingo, a functional morphologist, one who studies an anatomical system and tries to figure out the mechanism of how it works.

"Sharks are the most primitive vertebrate with jaws," Wilga explains. "Studying them is a good place to start to give us some basic knowledge and help us understand how biting and suction feeding mechanisms have evolved in higher vertebrates."

Sharks, by the way, don’t have the market on suctioning. While suctioning doesn’t work well in air —imagine eating dinner with a straw—it does work well in aquatic habitats. Remember Jonah? The whale suctioned him. Some turtles and most bony fishes are suctioners as well.

Wilga will focus her research on bamboo sharks, cat sharks and skates. While both the bamboo sharks and skates suction their food, they have different mechanisms to generate suction. Wilga will also study chain cat sharks, which are known for capturing their prey by opening their mouths and biting, a very different mechanism than suction. Remember Jaws?

The URI professor will attempt to answer such questions as: How do sharks suction? What about their anatomy makes them good bite or suction feeders? How much do they have to expand their mouths and throats to successfully capture various kinds of prey? How much pressure do they exert on their prey?

Her integrative approach combines several techniques to allow a fuller understanding of the relationship between anatomy, muscular effort, suction generation, feeding mechanism and water flow. She will attempt to quantify the water flow around and into the mouths of the three species by using a new technique to biology –engineers have used the technique for years--called digital particle image velocimetry or DPIV, which will measure the pattern of water flow.

Since bamboo sharks can polish off a meal in 60 milliseconds and one thousand milliseconds equals one second, you can’t see much with the naked eye. Wilga will employ high-speed video, which produces 500 images every second, which she will then download into her computer to slow down the action to see what the shark is doing and how it is doing it.