(Milne-Edwards, 1841)
Description
External appearance
Colonial, with zooids immersed. Colonies forming soft, gelatinous, thin sheets (less then 2 mm thick). Test transparent, sometimes with brown or grey pigmented cells, without calcareous spicules.
Characters
Zooids up to 2 mm in length; body divided into thorax and abdomen. Oral siphon 6-lobed; atrial opening large, exposing much of the branchial sac. Up to 24 thin branchial tentacles of variable size. Branchial sac bearing 4 rows of straight stigmata; without longitudinal bars or folds. Retractor muscle well-developed, extending from the posterior end of the thorax. Gut abdominal; stomach smooth. Gonads left of gut; testis bilobed; sperm duct not coiled; ovary beside testis (D. listerianum zooid).
Habitat
Attached to hard substrata; from low water level to depth of about 80 metres.
Distribution
Almost cosmopolitan.