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Pyrosoma atlanticum is a species of deep-water colonial tunicate found in oceans around the world. The colony forms a hollow cylinder that can grow up to 60 cm (24 in) long. The constituent zooids, which may be pink, yellowish, or bluish, form a rigid tube; each zooid has a pair of luminescent organs which can be turned on and off, causing a rhythmic flashing. No neural pathway runs between the zooids, but each responds to the light produced by other individuals, and even to light from nearby colonies. This P. atlanticum colony was photographed in a tide pool in Pacific Grove, California.Photograph credit: Rhododendrites