Urochordata

Definition

Urochordata, also known as tunicates, are a subphylum of chordates characterized by their sac-like body structure. They exhibit a notochord during their larval stage which is lost in adulthood when they become sessile.

5 Must Know Facts For Your Next Test

1. Urochordates possess a notochord only during their larval stage.
2. Adult urochordates are sessile and have a sac-like body enclosed in a tunic made of cellulose-like substance.
3. They undergo a dramatic metamorphosis from free-swimming larvae to sedentary adults.
4. Urochordates filter feed by drawing water through an incurrent siphon and expelling it through an excurrent siphon.
5. Their closest relatives within the phylum Chordata are the Cephalochordata and Vertebrata.

Review Questions

Related terms

Cephalochordata:

A subphylum of chordates known for retaining their notochords throughout life, exemplified by lancelets.

Notochord: A flexible rod made out of a material similar to cartilage that provides support in all embryonic and some adult chordate animals.

Metamorphosis:

The biological process where an animal physically develops after birth or hatching, involving a conspicuous change in body structure.