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Tunicates
Tunicates
Tunicates are present-day marine organisms named for their tough outer tunic or skin. They belong to the phylum Chordata and the subphylum Uruchordata ("basal- chordates").
The phylum of chordates is named for the notochord, a flexible rod that fits inside a hollow nerve cord. It runs from the head to the tail, lengthening and stiffening the body so that it can be flexed from side to side by the muscle blocks for swimming. The three groups of the chordate phylum, including tunicates, lancelets, and vertebrates, belong to three subphyla. Of these, the subphylum Urochordata includes present-day tunicates.
Tunicates
are marine filter feeders whose adult forms are typically sessile
(attached to the substrate), although some species float around freely.
Adult tunicates feed on organic debris and microorganisms drawn in by a
siphon, which passes through the pharynx. Tunicate larvae, by
contrast, resembling tiny tadpoles, have a head and tail, and a
well-developed notochord with a hollow nerve cord, helping them swim
around freely. On maturation they attach themselves to a substrate,
anchored by three adhesive papillae on the head. Adult tunicates
reabsorb their larval tail and notochord, and live as stationary
filter-feeders.
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