What is "tunicate"

Tunicate \Tu"ni*cate\, Tunicated \Tu"ni*ca`ted\, a. [L. tunicatus, p. p. of tunicare to clothe with a tunic, fr. tunica a tunic.]

1. (Bot.) Covered with a tunic; covered or coated with layers; as, a tunicated bulb.

2. (Zo["o]l.)

   1. Having a tunic, or mantle; of or pertaining to the Tunicata.

   2. Having each joint buried in the preceding funnel-shaped one, as in certain antenn[ae] of insects.

Tunicate \Tu"ni*cate\, n. (Zo["o]l.) One of the Tunicata.

1760, from Latin tunicatus "clothed with a tunic only (i.e. without a toga), in shirt-sleeves," past participle of tunicare "to clothe in a tunic," from tunica (see tunic). As a noun, from 1848.

a. 1 Of or pertaining to these animals. 2 (context anatomy botany English) Enclosed in a tunic or mantle; covered or coated with layers. 3 (context zoology English) Having each joint buried in the preceding funnel-shaped one, as in certain antennae of insects. n. Any of very many chordate marine animals, of the subphylum ''Tunicata'' or ''Urochordata'', including the sea squirts.

n. primitive marine animal having a saclike unsegmented body and a urochord (a notochord) conspicuous in the larva [syn: urochordate, urochord]

A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata, which is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords. The subphylum was at one time called Urochordata, and the term urochordates is still sometimes used for these animals. Some tunicates live as solitary individuals, but others replicate by budding and become colonies, each unit being known as a zooid. They are marine filter feeders with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. During their respiration and feeding, they take in water through the incurrent (or inhalant) siphon and expel the filtered water through the excurrent (or exhalant) siphon. Most adult tunicates are sessile and are permanently attached to rocks or other hard surfaces on the ocean floor; others, such as salps, doliolids and pyrosomes, swim in the pelagic zone of the sea as adults. Various species are commonly known as sea squirts, sea pork, sea livers, or sea tulips.

The earliest unequivocal species of tunicate appears in the fossil record in the early Cambrian period. Despite their simple appearance and very different adult form, their close relationship to the vertebrates is evidenced by the fact that during their mobile larval stage, they possess a notochord or stiffening rod and resemble a tadpole. Their name derives from their unique outer covering or "tunic" which is formed from proteins and carbohydrates and acts as an exoskeleton. In some species, it is thin, translucent, and gelatinous, while in others it is thick, tough, and stiff.