''Ciona intestinalis'' (sometimes known by the common name of vase tunicate) is an ascidian (sea squirt), a

tunicate Tunicates are marine invertebrates belonging to the subphylum Tunicata ( ). This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time ...

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 The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascular system. ...

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 An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

. Although Linnaeus first categorised this species as a kind of mollusk,

Alexander Kovalevsky Alexander Onufrievich Kovalevsky (; 7 November 1840 – 1901) was a Russian embryologist, who studied medicine at the University of Heidelberg and became professor at the University of St Petersburg. He was the brother of the paleontologist V ...

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 A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

has been sequenced using a specimen from

Half Moon Bay Half Moon Bay is a coastal city in San Mateo County, California, San Mateo County, California, United States, approximately south of San Francisco. Its population was 11,795 2020 United States census, 2020 census. Immediately north of Half Mo ...

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.

Description

''Ciona intestinalis'' is a solitary tunicate with a cylindrical, soft, gelatinous body, up to long. The body colour and colour at the distal end of siphons are major external characters distinguishing sister species within the species complex. 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).

Ecology

''Ciona intestinalis'' is a hermaphroditic broadcast spawner but cannot self-fertilize. 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

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.

Sexual reproduction

''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. 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. Self-incompatibility promotes out-crossing which provides the adaptive advantage at each generation of masking deleterious recessive mutations (i.e. genetic complementation).

Cell signalling

In the sea squirt ''C. intestinalis'' a CB1 and CB2-type cannabinoid receptors is found to be targeted to

axons An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see spelling differences) is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action pot ...

, indicative of an

ancient Ancient history is a time period from the beginning of writing and recorded human history through late antiquity. The span of recorded history is roughly 5,000 years, beginning with the development of Sumerian cuneiform script. Ancient h ...

role for cannabinoid receptors as

axon An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, ...

al regulators of

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

signalling A signal is both the process and the result of transmission of data over some media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology. In ...

Genetics

''Ciona intestinalis'' was one of the first animals to have its full

sequenced, in 2002. It has a relatively small genome (about 160 Mbp) consisting of 14 pairs of

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

s with about 16,000 genes.

Hox genes

The draft genome analysis identified nine

Hox gene Hox genes, a subset of homeobox, homeobox genes, are a gene cluster, group of related genes that Evolutionary developmental biology, specify regions of the body plan of an embryo along the craniocaudal axis, head-tail axis of animals. Hox protein ...

s, which are Ci-Hox1, 2, 3, 4, 5, 6, 10, 12, and 13. '' Ciona robusta'', 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.Ikuta, Tetsuro, and Hidetoshi Saiga. "Organization of Hox genes in ascidians: Present, past, and future." Developmental Dynamics 233.2 (2005): 382-89.

GEVIs

A majority of

genetically encoded voltage indicator Genetically encoded voltage indicator (or GEVI) is a protein that can sense membrane potential in a cell and relate the change in voltage to a form of output, often Fluorescence, fluorescent level. It is a promising Optogenetics, optogenetic record ...

are based on the ''C. intestinalis'' voltage-sensitive domain (Ci-VSD).

Transferrin

There is one

transferrin Transferrins are glycoproteins found in vertebrates which bind and consequently mediate the transport of iron (Fe) through blood plasma. They are produced in the liver and contain binding sites for two Iron(III), Fe3+ ions. Human transferrin is ...

ortholog which is divergent from those of

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

models, and even more divergent from non-

chordate A chordate ( ) is a bilaterian 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 ot ...

Carotenoid metabolism

A retinol dehydrogenase is disclosed in Belyaeva et al. 2015. .

References

External links

MarLIN
detailed species review
ANISEED
the Tunicate model organism database

from

Kyoto University , or , is a National university, national research university in Kyoto, Japan. Founded in 1897, it is one of the former Imperial Universities and the second oldest university in Japan. The university has ten undergraduate faculties, eighteen gra ...

Four-dimensional Ascidian Body Atlas
from

Keio University , abbreviated as or , is a private university, private research university located in Minato, Tokyo, Japan. It was originally established as a school for Rangaku, Western studies in 1858 in Edo. It was granted university status in 1920, becomi ...

* ''Ciona intestinalis'' protein database: https://web.archive.org/web/20071101003737/http://cipro.ibio.jp/ CIPRO from ibio.jp
intestinalis'' photos
from ascidians.com *View th
''Ciona intestinalis'' genome
in Ensembl * {{Authority control Phlebobranchia Animals described in 1767 Animal models Cosmopolitan animals Taxa named by Carl Linnaeus