Photos: The Surprising World of Sea Squirts

Sea squirts look like sponges or plants, but they're marine invertebrates, and some -- especially those that are bioluminous -- can be a stunning underwater find.

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Sea squirts are filter feeders, often found near coastal areas. Their transparent outer body gives them the appearance of a sponge or plant, but they're actually marine animals. As NOAA celebrates "30 Days of the Ocean" in June, we take a look at some of these bioluminous, stunning underwater finds.

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Free-swimming in the larval stage, adult sea squirts take root by attaching to coral, rock, shells or another hard surface.

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There are about 2,300 species of sea squirts, and though they are solitary creatures they form colonies that can be several meters wide.

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They are are also, to some folks, pretty tasty. Above, sea squirts go on display at a market in Korea.

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Sea squirts have two "siphons" at the top of their body -- one to suck in water and one to, well, squirt it out. Above, a light bulb sea quirt (

Keulenseescheide Ascidia

) handles its business.

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The sea salp is not a sea squirt, but it is a species of tunicate, and no slouch in the bioluminescence department.

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Here you can see the flow opening of a red sea squirt (

Halocynthia papillosaut)


Sea squirts can grow up to 7 inches (18 centimeters) in diameter and are also able to heal damaged parts by regenerating cells.

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The sea squirt's healing abilities have prompted researchers to study them, with the hopes that they might help cure diseases such as Alzheimer's and heart disease in people.

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