''Ciona'' is a genus of sea squirts in the family

Cionidae Cionidae is a family of sea squirts belonging to the suborder Phlebobranchia Phlebobranchia is a suborder of tunicate, sea squirts in the class Ascidiacea. Characteristics The group includes both colonial and solitary animals. They are di ...

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

tunic A tunic is a garment for the body, usually simple in style, reaching from the shoulders to a length somewhere between the hips and the knees. The name derives from the Latin ''tunica'', the basic garment worn by both men and women in Ancient Rome ...

, 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 epidermis 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 or ...

) and

atrial The atrium ( la, ātrium, , entry hall) is one of 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 valves. There are two at ...

( cloacal) siphons. The water is drawn into the

ascidian Ascidiacea, commonly known as the ascidians, tunicates (in part), and sea squirts (in part), is a polyphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" m ...

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 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 op ...

'' * '' Ciona fascicularis'' * '' 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 op ...

'' * '' Ciona imperfecta'' * '' Ciona intermedia'' * '' Ciona intestinalis'' * '' Ciona longissima'' * '' Ciona mollis'' * '' Ciona pomponiae'' * ''

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 intestin ...

'' * ''

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 op ...

'' * ''

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 op ...

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

'' C. intestinalis'' is a hermaphrodite 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 which has the potential to result from inbreeding (the breeding of related individuals). Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. ...

, 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 can be a usefu ...

which allows the masking of deleterious recessive mutations.

References

External links

The Tunicate Portal
an access point to the main websites and databases dealing with tunicates
Ascidians.com
pictures of species around the world
ANISEED
a model organism database for several ascidians species including ''Ciona intestinalis'' and ''Halocynthia roretzi''
JGI Ciona intestinalis v2.0
genome sequence * Enterogona Tunicate genera {{tunicata-stub