Ciona Explained

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 opposite bears two openings, the buccal (oral) and atrial (cloacal) siphons. The water is drawn into the ascidian through the buccal siphon and leaves the atrium through the atrial siphon.

Species

Species in this genus include:^[1]

• Ciona antarctica
• Ciona edwardsi
• Ciona fascicularis
• Ciona gelatinosa
• Ciona hoshinoi
• Ciona imperfecta
• Ciona intermedia
• Ciona intestinalis
• Ciona longissima
• Ciona mollis
• Ciona pomponiae
• Ciona robusta
• Ciona roulei
• Ciona savignyi
• Ciona sheikoi

Genome projects

As of 2008, the genomes of Ciona intestinalis^[2] and Ciona savignyi^[3] have been sequenced.

Sexual reproduction

Ciona 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.^[4] C. savigny is highly self-fertile, but non-self sperm out-compete self-sperm in fertilization competition assays.^[5] Mechanisms promoting non-self fertilization may have evolved to avoid inbreeding depression, and to facilitate outcrossing which allows the masking of deleterious recessive mutations.^[6]

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'.^[7]

Notes and References

1. Web site: WoRMS - World Register of Marine Species - Ciona Fleming, 1822. www.marinespecies.org. en. 2021-05-10.
2. 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
3. http://mendel.stanford.edu/sidowlab/ciona.html The C. savignyi Reference Genome and Genetic Map
4. Sawada H, Morita M, Iwano M . Self/non-self recognition mechanisms in sexual reproduction: new insight into the self-incompatibility system shared by flowering plants and hermaphroditic animals . Biochem. Biophys. Res. Commun. . 450 . 3 . 1142–8 . August 2014 . 24878524 . 10.1016/j.bbrc.2014.05.099 .
5. Jiang D, Smith WC . Self- and cross-fertilization in the solitary ascidian Ciona savignyi . Biol. Bull. . 209 . 2 . 107–12 . October 2005 . 16260770 . 10.2307/3593128. 3593128 .
6. Bernstein H, Byerly HC, Hopf FA, Michod RE . Genetic damage, mutation, and the evolution of sex . Science . 229 . 4719 . 1277–81 . September 1985 . 3898363 . 10.1126/science.3898363.
7. Web site: 'It should not taste marine-like': Would you eat a burger made from processed sea squirts? . Lie-Nielsen K . The Guardian . November 12, 2024 .