Carbasea carbasea is a boreal and artic species that occurs throughout Britain, Ireland, and the North Sea. C. carbasea forms small erect tufts up to 12 cm high which are light brown to yellowish in colour with a paper-like texture. The fronds are flattened, but broaden into rounded lobes towards the tip. The fronds of C. carbasea are less palmate and typically more delicate and flexible than those of Flustra.
Carbasea carbasea attaches to hard substrates including stones and shells by an encursting basal portionof the colony. Colonies are predominantly found in the subtidal, but may often be washed-up along the coastline, particularly after storms.
Like all bryozoans, C. carbasea colonies grow through asexual budding of new zooids at the periphery.
Carbasea carbasea is often mistaken for seaweed, however, closer inspection of the fronds will reveal the very apparent zooids, confirming the colony as an animal species. Several other bryozoans are similar in shape and habitat to C. carbasea including species of Flustra. Colonies of C. carbasea may be distinguished by their more delicate, flexible and paper-like texture compared to colonies of Flustra. Fronds of C. carbasea are unilaminar while Flustra is bilaminar and the zooids of C. carbasea lack the spines which may be observed on Flustra.
Colonies form small tufts of radiating fronds that branch in a somewhat dichotomous formation. The fronds are flattened and terminate in rounded lobes. The colony narrows towards the base, terminating in a small disk of encrusting zooids, by which it adheres to the substrate. Carbasea carbasea is lightly calcified and the colony as whole is flexible, allowing it to move with the current. Fronds of C. carbasea are unilaminar, comprising only one sheet of zooids. Zooids are simple rectangles, sometimes expanded slightly in the middle. The frontal surface is entirely membranous and no gymnocyst is present. A thin, very narrow shelf of calcification, which is a vestige of a cryptocyst, may occur beneath the frontal membrane at the proximal end of the zooid, closest to the colony origin. The lateral and distal walls of the zooids are lightly calcified. The polypide has 20-25 tentacles and avicularia are absent.
Opercula (flap-like folds of the body wall which close the orifice) are well chitinized and appear light brown in colour. Specialised zooids, which lack feeding apparatus (kenozooids) border the edge of the fronds. The kenozooids are narrow and approximately twice the length of normal zooids.
Colonies typically grow to up to 12 cm. Zooids are large: 0.9 – 1.2 mm by 0.4 mm
Carbasea carbasea occurs throughout Britain, Ireland, the Bering Sea and the North Sea. Colonies have also been recorded from Norway, Germany, Belgium and Danemark, extending in to Skaggerak and Kattegat.
Carbasea carbasea is an arctic and boreal species that is most frequently found on stones and shells in the subtidal. Carbasea carbasea has been recorded from brackish environments in the Kattegat area of the Baltic Sea (Winston, 1977).
The founding zooid (ancestrula) develops into a young colony, and later into an adult colony through asexual budding. Sexually produced embryos are brooded within the colony, before larvae are released. Larvae settle after liberation and metamorphose into an ancestrula.
Like all bryozoans, C. carbasea is a suspension feeder. It feeds on small phytoplankton using ciliated tentacles of the lophophore.
Ovicells do not occur in this species; instead embryos develop in ovisacs within the maternal zooids. Egg formation within the zooid is accompanied by degeneration of the polypide, which may then regenerate after release (Ostrovsky et al. 2008)