Ciona
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: Genome projects. As of 2008, the genomes of "Ciona intestinalis" and "Ciona savignyi" 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, and to facilitate outcrossing which allows the masking of deleterious recessive mutations.