The Ciona intestinalis, and all tube tunicates, are thought to occupy a special evolutionary position because they contain a notochord and branchial basket, structures found mainly in chordates (Larousse 1967).
The Ciona intestinalis are not an endangered species; therefore, there are no conservation details on them.
US Federal List: no special status
CITES: no special status
Ciona intestinalis are problematic for marine aquaria keepers because they settle within the metal plumbing pipes and filters; this does not occur when these structures are made of plastic (Nichols and Cooke 1971). The concentration of them on piers, pilings, buoys, and ship hulls can also be a nuisance to humans (Coleman 1991, Larousse 1967).
The Ciona intestinalis has no known benefit for humans.
Ciona intestinalis feed mainly on fine detrital particles and phytoplankton (Coleman 1991). During the cirulation of water through the large gill basket, food particles are taken from the water and the endostyle secretes mucus to trap the food. It is then passed to the dorsal midline of the pharynx where it is rolled into a mucus rope and passed to the stomach. From here it passes to the intestine, and the faecal pellets formed go from the anus to the atrial opening where they are expelled from the body (Larousse 1967).
Ciona intestinalis is well distributed throughout the world, including many European oceans (Ricketts, et al 1985).
Ciona intestinalis are usually found in silty conditions in 0-500 meters (1640 feet) of water. Most are found near rocky shores and estuaries, where the tide of the ocean meets a river current. They are often found growing in great numbers on manmade structures such as piers, pilings, and even in marine aquaria (Coleman 1991). They, and many other species in the class Ascidiacea, are also "common fouling organisms" on buoys, pier-piles, and hulls (Larousse 1967).
All the animals in the family Cionidae are called tunicates because they have a "tunic" of cellulose-like substance that covers the body. In this tunic are scattered cells, nerves, and blood vessels (Larousse 1967). The animals in the genus Ciona are known for their soft tunics and flexible bodies because the upper part of their bodies can be drawn into the lower part, "like the finger of a glove" (Nichols and Cooke 1971). A branching vascular system is interlaced within the entire tunic, which makes up about 60% of the animal's weight (Grzimek 1972).
The Ciona intestinalis grows to be about 120 mm (5 in) high and is simple and elongated. It is a sessile, usually attached to a substrate such as seeweed, solitary, and non-colonial organism. It is greenish, translucent, and tubular with terminal inhalent and sub-terminal exhalent siphons (openings). The inhalent siphon is surrounded by eight distinct lobes and the exhalent siphon by six; the lobes are interposed with red or orange pigment spots. The retractor muscles, gut, gonads, and large filter-feeding and respiratory pharynx can sometimes be seen through the body wall (Coleman 1991).
The pharynx has a ring of tentacles at the beginning that prevents large objects from entering it. It then gets larger, and the walls contain many gill slits lined with cilia. The sweeping movement of these cilia sets up the current circulation of water from the pharynx to the alimentary canal and back out to the exterior. An organ known as the endostyle lies on the floor of the branchial chamber; it is believed to be the precursor to the thyroid gland. The endostyle secretes mucus that traps food particles, and then the cilia lining the endostyle pass the mucus to the dorsal midline of the pharynx "where it is rolled into a mucus rope" (Larousse 1967). The rope is then passed to the oesophagus, stomach, and intestine, and faecal pellets are discharged through the atrial opening. These animals contain few blood vessels, no capillaries, and the circulatory system is made up of haemocoelic cavities. The neural gland contains the gonatropic substances and is thought to match the pituitary gland in vertebrates (Larousse 1967).
The larva of the Ciona intestinalis is dispersive, lasting only 36 hours. It contains a notochord within its muscular tail that is lost at metamorphosis, a dorsal nerve cord, a brain and sense-organs. In its life-history, the tunicate shows retrogressive evolution because the larva contains more features similar to the vertebrates than the adult does (Larousse 1967).
The life span of most ascidians is about one year (Grzimek 1972). The Ciona intestinalis is hermaphroditic and releases sperm and eggs through the exhalent siphon. Fertilization occurs at sea, and a tadpole-like larva is formed about 25 hours later. The larva lasts about 36 hours, depending on the temperature of the area, after which it settles and metamorphoses into an adult (Coleman 1991).
Ciona intestinalis (sometimes known by the common name of vase tunicate) is an ascidian (sea squirt), a tunicate with very soft tunic. Its Latin name literally means "pillar of intestines", referring to the fact that its body is a soft, translucent column-like structure, resembling a mass of intestines sprouting from a rock.[1] It is a globally distributed cosmopolitan species. Since Linnaeus described the species, Ciona intestinalis has been used as a model invertebrate chordate in developmental biology and genomics.[2] Studies conducted between 2005 and 2010 have shown that there are at least two, possibly four, sister species.[3][4][5] More recently it has been shown that one of these species has already been described as Ciona robusta.[6] By anthropogenic means, the species has invaded various parts of the world and is known as an invasive species.[7][8]
Although Linnaeus first categorised this species as a kind of mollusk, Alexander Kovalevsky found a tadpole-like larval stage during development that shows similarity to vertebrates. Recent molecular phylogenetic studies as well as phylogenomic studies support that sea squirts are the closest invertebrate relatives of vertebrates.[9] Its full genome has been sequenced using a specimen from Half Moon Bay in California, US,[10] showing a very small genome size, less than 1/20 of the human genome, but having a gene corresponding to almost every family of genes in vertebrates.
Ciona intestinalis is a solitary tunicate with a cylindrical, soft, gelatinous body, up to 20 centimetres (8 in) long. The body colour and colour at the distal end of siphons are major external characters distinguishing sister species within the species complex.[11]
The body of Ciona is bag-like and covered by a tunic, which is a secretion of the epidermal cells. The body is attached by a permanent base located at the posterior end, while the opposite extremity has two openings, the buccal and atrial siphons. Water is drawn into the ascidian through the buccal (oral) siphon and leaves the atrium through the atrial siphon (cloacal).
Ciona intestinalis is a hermaphroditic broadcast spawner but cannot self-fertilize.[12] Eggs and sperm, when released, can stay in the water column for 1 to 2 days, while the larvae are free-swimming for 2 to 10 days.
Ciona intestinalis is considered to be an invasive species and grows in dense aggregations on any floating or submerged substrate, particularly artificial structures like pilings, aquaculture gear, floats and boat hulls, in the lower intertidal to sub-tidal zones. It often grows with or on other fouling organisms. It is thought to spread to new areas mainly through hull fouling. Since its larvae can live for up to 10 days, this species may also be transferred through the release of bilge or ballast water.
The potential impact of C. intestinalis and its introduction to new habitats can be avoided, so most agencies suggest that fish and shellfish harvesters are to avoid transfer of harvested shellfish and fishing gear to other areas, and to dry gear thoroughly before transfer, along with inspecting boat hulls. They also recommend that, if necessary, to clean them thoroughly, and to disinfect with bleach or vinegar and dry them before moving to other areas. Agencies also recommended the disposal of any organisms removed from boat hulls or gear on land and to release bilge water on land or disinfect it.
Ciona intestinalis is an hermaphrodite that releases sperm and eggs into the surrounding seawater almost simultaneously. C. intestinalis is self-sterile, and thus has been used for studies on the mechanism of self-incompatibility.[13] Self/non-self-recognition molecules are considered to play a key role in the process of interaction between sperm and the vitelline coat of the egg. It appears that self/non-self recognition in ascidians such as C. intestinalis is mechanistically similar to self-incompatibility systems in flowering plants.[13] Self-incompatibility promotes out-crossing which provides the adaptive advantage at each generation of masking deleterious recessive mutations (i.e. genetic complementation).[14]
In the sea squirt C. intestinalis a CB1 and CB2-type cannabinoid receptors is found to be targeted to axons, indicative of an ancient role for cannabinoid receptors as axonal regulators of neuronal signalling.[15]
Ciona intestinalis was one of the first animals to have its full genome sequenced, in 2002. It has a relatively small genome (about 160 Mbp) consisting of 14 pairs of chromosomes with about 16,000 genes.[16]
The draft genome analysis identified nine Hox genes, which are Ci-Hox1, 2, 3, 4, 5, 6, 10, 12, and 13.[10] Ciona savignyi, the closest relative of Ciona intestinalis, also has the same set of Hox genes. The organization of Hox genes is only known for C. intestinalis among ascidians. The nine Hox genes are located on two chromosomes; Ci-Hox1 to 10 on one chromosome and Ci-Hox12 and 13 on another. The intergenic distances within the Ciona Hox genes are extraordinarily long. Seven Hox genes, Ci-Hox1 to 10, are distributed along approximately half the length of the chromosome. Comparisons to Hox gene expression and location in other species suggests that the Hox genes in ascidian genomes are under a dispersing condition.[17]
A majority of genetically encoded voltage indicator are based on the C. intestinalis voltage-sensitive domain (Ci-VSD).
There is one transferrin ortholog which is divergent from those of vertebrate models, and even more divergent from non-chordates.[18]
A retinol dehydrogenase – CiRdh10 – is disclosed in Belyaeva et al. 2015.[19]
Ciona intestinalis (sometimes known by the common name of vase tunicate) is an ascidian (sea squirt), a tunicate with very soft tunic. Its Latin name literally means "pillar of intestines", referring to the fact that its body is a soft, translucent column-like structure, resembling a mass of intestines sprouting from a rock. It is a globally distributed cosmopolitan species. Since Linnaeus described the species, Ciona intestinalis has been used as a model invertebrate chordate in developmental biology and genomics. Studies conducted between 2005 and 2010 have shown that there are at least two, possibly four, sister species. More recently it has been shown that one of these species has already been described as Ciona robusta. By anthropogenic means, the species has invaded various parts of the world and is known as an invasive species.
Although Linnaeus first categorised this species as a kind of mollusk, Alexander Kovalevsky found a tadpole-like larval stage during development that shows similarity to vertebrates. Recent molecular phylogenetic studies as well as phylogenomic studies support that sea squirts are the closest invertebrate relatives of vertebrates. Its full genome has been sequenced using a specimen from Half Moon Bay in California, US, showing a very small genome size, less than 1/20 of the human genome, but having a gene corresponding to almost every family of genes in vertebrates.
