Urochordata

A Dictionary of Zoology

Urochordata (sea squirts, tunicates; phylum Chordata) A subphylum that has a reliable fossil record from the Permian, and possible remains in Silurian sediments. Urochordates have tadpole-like larvae with notochords in their tails and a dorsal, tubular nerve cord, features that link them with the Chordata. The adults have a gelatinous or leathery protective test (the tunic) made from a chemical very similar to the cellulose found in plants. The tunic has two openings, allowing water to flow through the gill slits in the pharynx. The water flow is maintained by ciliated cells, and food is trapped by mucus on the pharyngeal gill slits.

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© A Dictionary of Zoology 1999, originally published by Oxford University Press 1999.

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	tunic tunic See UROCHORDATA . Read more
	tunicates tunicates See UROCHORDATA . Read more

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