Lahille, 1887
Ciona, the only known genus of this family, is characterised by its solitary habit, horizontal gut loop posterior to the thorax, persistent openings of the epicardial sacs into the pharynx, lobed apertures, and a large branchial sac with numerous rows of stigmata and internal longitudinal vessels supported on papillae which project into the lumen.
Kott (1969) first drew attention to the aplousobranch nature of the Cionidae, which formerly had been included (with the Diazonidae) in the Phlebobranchia on the basis of the internal longitudinal branchial vessels and their supporting papillae which are similar to those of certain phlebobranch ascidians (a.o., Berrill, 1950). A tendency to lose internal longitudinal branchial vessels is a convergent adaptation associated with the development of vegetative replication and consequent reduction in zooid size in both phlebobranch and stolidobranch as well as in aplousobranch ascidians (Kott, 1985, 1990).
Source: Kott, 1990.
Treated taxon:
- genus Ciona