Chordates

Chordata Characteristics

General Traits

  1. Chordata are classified as deuterostome coelomates.

  2. Their closest relatives are echinoderms, which are the only other known deuterostomes.

Key Features

  1. Chordata possess four defining features:

    • Nerve Cord: A hollow structure that forms the central nervous system.

    • Notochord: A flexible rod-like structure that provides support.

    • Pharyngeal Slits: Openings in the pharynx that can serve various functions, including filter feeding in some species.

    • Postanal Tail: An extension of the body past the anal opening, present at some stage of development.

  2. All four traits are present at some point during the development of Chordata species.

Subphylum Divisions

  • Chordata can be classified into three primary groups (formerly known as subphyla):

    • Urochordata: Non-vertebrates, commonly known as tunicates.

    • Cephalochordata: Also non-vertebrate, comprising lancelets.

    • Vertebrata: Includes all vertebrate animals, characterized by having a backbone.

Urochordata Details

General Information

  1. Tunicates belong to this subgroup and are primarily marine organisms.

  2. The larval stage of tunicates is characterized by a tadpole-like form that includes both a notochord and a nerve cord.

  3. Adult tunicates undergo significant changes:

    • Typically lose the tail and notochord during transformation.

    • Adult forms are sessile and act as filter feeders, drawing water through an incurrent siphon for feeding.