Definition

Noun: A urochordate is a primitive marine animal characterized by a sac-like, unsegmented body. As a chordate, it possesses a notochord (a flexible skeletal rod) at some stage in its life cycle. In urochordates, this structure, specifically called a urochord, is most prominent during the larval stage.

Usage and Examples

• The sea squirt is a common example of a urochordate.
• During their larval phase, urochordates exhibit a defining chordate body plan, which is often lost or greatly modified in the adult form.
• The study of urochordates provides important insights into early chordate evolution.

Advanced Usage

• Taxonomic Context: In scientific classification, Urochordata is a subphylum within the phylum Chordata, making the term urochordate synonymous with tunicate.
• Developmental Biology: The transformation of a free-swimming urochordate larva into a sessile (attached) adult involves a dramatic metamorphosis, a key area of research.

Variants and Related Words

• Tunicate (n): Another name for a urochordate, referring to the tough, cellulose-containing "tunic" that surrounds the adult's body.
• Urochordata (n): The scientific subphylum name for this group of animals.
• Ascidian (n): A common type of sessile urochordate, such as a sea squirt.

Synonyms

• Tunicate

Related Terms and Concepts

• Chordate: The broader phylum to which urochordates belong, sharing the defining feature of a notochord.
• Notochord: The flexible rod that provides skeletal support, present in the tails of urochordate larvae.
• Sessile: A term describing the attached, non-moving lifestyle of most adult urochordates.

Noun

1. primitive marine animal having a saclike unsegmented body and a urochord that is conspicuous in the larva