Tunicate
Tunicate
Tunicate (pronunciation: /ˈtjuːnɪkeɪt/), also known as Urochordata (pronunciation: /ˌjʊəroʊkɔːrˈdeɪtə/), is a subphylum of invertebrate animals, a member of the phylum Chordata. The name "tunicate" derives from the unique outer covering or "tunic" that these organisms possess.
Etymology
The term "tunicate" is derived from Latin tunica, meaning "coat" or "cloak", referring to the thick, non-living outer layer, or tunic, that covers the animal's body. The term "Urochordata" is derived from the Greek words oura meaning "tail" and khordē meaning "cord", referring to the tail-like structure present in the larval stage of these animals.
Anatomy
Tunicates are characterized by a sac-like body enclosed in a tunic, which is composed of a cellulose-like substance called tunicin. They possess two siphons, the buccal (or incurrent) siphon and the atrial (or excurrent) siphon, which are used for the intake and expulsion of water, respectively. Inside the tunicate's body is a pharynx lined with cilia, which filters food particles from the water.
Life Cycle
The life cycle of a tunicate involves a larval stage and an adult stage. The larvae are free-swimming and possess a notochord, a dorsal nerve cord, and a post-anal tail, all of which are characteristic features of the phylum Chordata. However, these features are lost when the larva metamorphoses into the sessile adult form.
Classification
Tunicates are classified into three classes: Ascidiacea (sea squirts), Thaliacea (salps), and Appendicularia (larvaceans). Each class is distinguished by specific morphological characteristics and life history traits.
Related Terms
- Chordata: The phylum to which tunicates belong.
- Tunicin: The cellulose-like substance that composes the tunic of tunicates.
- Ascidian: Another term for sea squirts, a class of tunicates.
- Salp: A class of tunicates known for their barrel-shaped bodies.
- Larvacean: A class of tunicates that retain their larval features throughout their life.
External links
- Medical encyclopedia article on Tunicate
- Wikipedia's article - Tunicate
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