Final answer:
The type of tunic do the urochordate tunicates have a barrel-shaped body and a tough outer covering called the tunic.
Step-by-step explanation:
Tunicates, also known as urochordates, have a unique type of tunic referred to as the tunic. The tunic is a cellulose-like carbohydrate material that covers the outer body of tunicates. It gives them their barrel-shaped appearance. The tunic serves as a protective covering and helps provide support to the body.
Tunicates are considered to be chordates, but as adults, they lack certain features typical of chordates, such as a notochord, a dorsal hollow nerve cord. However, tunicates do possess pharyngeal slits and an endostyle, which are characteristic of chordates.
Therefore tunicates (urochordates) have a unique tunic that covers their outer body. As adults, they lack certain chordate features but have pharyngeal slits and an endostyle.