A chordate is a deuterostomic bilaterial animal belonging to the phylum Chordata. All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa. These five synapomorphies are a notochord, a hollow dorsal nerve cord, an endostyle or thyroid, pharyngeal slits, and a post-anal tail.
A tunicate is an exclusively marine invertebrate animal, a member of the subphylum Tunicata. This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords. The subphylum was at one time called Urochordata, and the term urochordates is still sometimes used for these animals. They are the only chordates that have lost their myomeric segmentation, with the possible exception of the seriation of the gill slits. However, doliolids still display segmentation of the muscle bands.
Larvaceans or appendicularians, class Appendicularia, are solitary, free-swimming tunicates found throughout the world's oceans. While larvaceans are filter feeders like most other tunicates, they keep their tadpole-like shape as adults, with the notochord running through the tail. They can be found in the pelagic zone, specifically in the photic zone, or sometimes deeper. They are transparent planktonic animals, usually ranging from 2 mm (0.079 in) to 8 mm (0.31 in) in body length including the tail, although giant larvaceans can reach up to 10 cm (3.9 in) in length.
Ascidiacea, commonly known as the ascidians or sea squirts, is a paraphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" made of a polysaccharide.
The Doliolida are an order of small marine chordates of the subphylum Tunicata. They are in the class Thaliacea, which also includes the salps and pyrosomes. The doliolid body is small, typically 1–2 mm long, and barrel-shaped; it features two wide siphons, one at the front and the other at the back end, and eight or nine circular muscle strands reminiscent of barrel bands.
Herdmania is a genus of ascidian tunicates in the family Pyuridae.
A salp or salpa is a barrel-shaped, planktonic tunicate in the family Salpidae. It moves by contracting, thereby pumping water through its gelatinous body; it is one of the most efficient examples of jet propulsion in the animal kingdom. The salp strains the pumped water through its internal feeding filters, feeding on phytoplankton.
Pyrosomes are free-floating colonial tunicates in family Pyrosomatidae. There are three genera, Pyrosoma, Pyrosomella and Pyrostremma, and eight species. They usually live in the upper layers of the open ocean in warm seas, although some may be found at greater depths.
Botryllus is a genus of colonial ascidian tunicates in the family Styelidae.
Botrylloides leachii is a colonial tunicate of the family Styelidae. Its unique methods of propagation and regeneration make it an ideal model organism for use in biological study of development, immunology, stem cells, and regeneration.
Pyrosoma atlanticum is a pelagic species of marine colonial tunicate in the class Thaliacea found in temperate waters worldwide. The name of the genus comes from the Greek words pyros meaning 'fire' and soma meaning 'body', referring to the bright bioluminescence sometimes emitted. The specific epithet atlanticum refers to the Atlantic Ocean, from where the first specimen of the species was collected for scientific description; it was described in 1804 by François Péron, a French naturalist.
Dolioletta gegenbauri is a species of tunicate in the family Doliolidae. It is small, exists in various forms and is sometimes found in great abundance in the Atlantic and Pacific waters where it lives.
Ecteinascidia turbinata, commonly known as the mangrove tunicate, is a species of tunicate in the family Perophoridae. It was described to science in 1880 by William Abbott Herdman. The cancer drug trabectedin can be isolated from this species.
Thetys vagina, or the twin-sailed salp, is the largest known solitary species of salp and the only valid species of the genus Thetys. First described by W.G Tilesius in 1802, the species is transparent and gelatinous, making it difficult to be seen in water, which is helpful in avoiding predators. The fossil range is very recent. Other animals often mistaken for T. vagina are Salpa fusiformis, Aurelia aurita, and Pegea confoederata. There is no known status of conservation in this species. T. vagina DNA was sequenced as part of a larger project in 2014 where spiny lobster larvae were found attached to T. vagina and consuming it.
Diazona violacea is a species of tunicate, an ascidian in the family Diazonidae. It is the type species of the genus Diazona.
Morchellium argus, the red-flake ascidian, is a species of colonial sea squirt, a tunicate in the family Polyclinidae. It is native to shallow water in the northeastern Atlantic Ocean, especially round the coasts of Britain.
Polyclinum planum is a compound ascidian commonly known as the elephant ear tunicate. It is an ascidian tunicate in the family Polyclinidae. Ascidians are also known as sea squirts.
Polyandrocarpa is a genus of ascidian tunicates within the family Styelidae.
Clavelina ossipandae, the skeleton panda sea squirt or skeleton panda ascidian, is a species of colonial ascidian, a group of sessile, marine filter-feeding invertebrates. Originally discovered near Kume Island in Japan by local divers, pictures of the animal attracted attention in the media for its appearance prior to its formal taxonomic description in 2024.
