''Ciona'' is a genus of

sea squirts 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 test or "tunic" made of the polysaccharid ...

in the family

Cionidae Cionidae is a family of sea squirts belonging to the order Phlebobranchia Phlebobranchia is an order of sea squirts in the class Ascidiacea, first described by Fernando Lahille in 1886. Characteristics The group includes both colonial an ...

. The body of ''Ciona'' is bag-like and covered by a

tunic A tunic is a garment for the torso, usually simple in style, reaching from the shoulders to a length somewhere between the hips and the ankles. It might have arm-sleeves, either short or full-length. Most forms have no fastenings. The name deri ...

, which is a secretion of the

epidermal The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the amount of water relea ...

cells. The body is attached at a permanent base located at the posterior part, and the opposite bears two openings, the buccal (

oral The word oral may refer to: Relating to the mouth * Relating to the mouth, the first portion of the alimentary canal that primarily receives food and liquid **Oral administration of medicines ** Oral examination (also known as an oral exam or ora ...

) and

atrial The atrium (; : atria) is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves. ...

(

cloaca A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...

siphon A siphon (; also spelled syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in an inverted "U" shape, which causes a liquid to flow upward, abo ...

s. The water is drawn into the

ascidian 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 test or "tunic" made of the polysaccharid ...

through the buccal siphon and leaves the

atrium Atrium may refer to: Anatomy * Atrium (heart), an anatomical structure of the heart * Atrium, the genital structure next to the genital aperture in the reproductive system of gastropods * Atrium of the ventricular system of the brain * Pulmona ...

through the atrial siphon.

Species

Species in this genus include: * ''

Ciona antarctica ''Ciona'' is a genus of sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunic, which is a secretion of the epidermal cells. The body is attached at a permanent base located at the posterior part, and the op ...

'' * ''

Ciona edwardsi ''Ciona'' is a genus of sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunic, which is a secretion of the epidermal cells. The body is attached at a permanent base located at the posterior part, and the o ...

'' * ''

Ciona fascicularis ''Ciona'' is a genus of tunicate, sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunica (biology), tunic, which is a secretion of the Squamous epithelium, epidermal cells. The body is attached at a permane ...

'' * '' Ciona gelatinosa'' * ''

Ciona hoshinoi ''Ciona'' is a genus of sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunic, which is a secretion of the epidermal cells. The body is attached at a permanent base located at the posterior part, and the o ...

'' * ''

Ciona imperfecta ''Ciona'' is a genus of tunicate, sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunica (biology), tunic, which is a secretion of the Squamous epithelium, epidermal cells. The body is attached at a permane ...

'' * ''

Ciona intermedia ''Ciona'' is a genus of sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunic, which is a secretion of the epidermal cells. The body is attached at a permanent base located at the posterior part, and the o ...

'' * ''

Ciona intestinalis ''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, tran ...

'' * ''

Ciona longissima ''Ciona'' is a genus of tunicate, sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunica (biology), tunic, which is a secretion of the Squamous epithelium, epidermal cells. The body is attached at a permane ...

'' * ''

Ciona mollis ''Ciona'' is a genus of sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunic, which is a secretion of the epidermal cells. The body is attached at a permanent base located at the posterior part, and the o ...

'' * ''

Ciona pomponiae ''Ciona'' is a genus of sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunic, which is a secretion of the epidermal cells. The body is attached at a permanent base located at the posterior part, and the o ...

'' * ''

Ciona robusta ''Ciona robusta'' is a species of marine invertebrate in the genus '' Ciona'' of the family Cionidae. The holotype was collected on the northeastern coast of Honshu Island, Japan. Populations of ''Ciona intestinalis'' known as ''Ciona intestinal ...

'' * ''

Ciona roulei ''Ciona'' is a genus of sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunic, which is a secretion of the epidermal cells. The body is attached at a permanent base located at the posterior part, and the o ...

'' * ''

Ciona savignyi ''Ciona savignyi'' is a marine animal sometimes known as the Pacific transparent sea squirt or solitary sea squirt. It is a species of tunicates in the family Cionidae. It is found in shallow waters around Japan and has spread to the west coast ...

'' * ''

Ciona sheikoi ''Ciona'' is a genus of sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunic, which is a secretion of the epidermal cells. The body is attached at a permanent base located at the posterior part, and the o ...

Genome projects

As of 2008, the genomes of ''Ciona intestinalis''P. Dehal et al.: ''The draft genome of Ciona intestinalis: insights into chordate and vertebrate origins.'' Science, 298, 5601, S. 2157–67, 13. Dezember 2002 and ''Ciona savignyi''The C. savignyi Reference Genome and Genetic Map
/ref> have been sequenced.

Sexual reproduction

'' is a

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

that releases sperm and eggs almost simultaneously into the surrounding seawater. ''C. intestinalis'' is self-sterile and thus has been used for studies on the mechanism of self-incompatibility. ''C. savigny'' is highly self-fertile, but non-self sperm out-compete self-sperm in fertilization competition assays. Mechanisms promoting non-self fertilization may have evolved to avoid

inbreeding depression Inbreeding depression is the reduced biological fitness caused by loss of genetic diversity as a consequence of inbreeding, the breeding of individuals closely related genetically. This loss of genetic diversity results from small population siz ...

, and to facilitate

outcrossing Out-crossing or out-breeding is the technique of crossing between different breeds. This is the practice of introducing distantly related genetic material into a breeding line, thereby increasing genetic diversity. Outcrossing in animals Out ...

which allows the masking of deleterious recessive mutations.

Use as food

''Ciona'' is being developed in Norway as a potential substitute meat protein, after processing to remove its 'marine taste' and to make its texture less 'squid-like'.

References

Phlebobranchia Tunicate genera {{tunicata-stub