(Linnaeus, 1758)
Description
This species forms large tree-like colonies which may be fixed or free; corallites connected by cylindrical branches of very dense peritheca. The growth form is variable, branches may anastomose where they converge. Corallites up to 12 mm diameter with strongly exsert, rather brittle septa irregularly arranged in three or four cycles. Columella and pali are absent.
Colouration: Polyps translucent: white, pink or yellowish, with up to 50 tentacles with obsolete terminal knobs.
Habitat
On rocky or soft bottoms usually in depths in excess of 150 m but occasionally in shallower inshore waters. Rarely found attached to solid substrata as the dead basal parts of the corallum are usually attacked by a boring sponge, Cliona sp., which weakens it, eventually causing breakage; therefore in most localities this coral forms large free clumps or patches up to 1 m high and 50 m across. The continual weakening action of the clionid sponges results in numerous small portions of the coral breaking away from the main mass. These form a substratum for the development of further colonies, thus extending the patches laterally.
Distribution
A deep-water Atlantic species ranging from Europe and west Africa to the east coast of North and South America; also recorded from Madagascar. Occurs mainly off the continental shelf and most British records are from west Scotland and Ireland; occasional specimens have been taken from deep (c. 50-100 m) inshore waters in Scotland. For further details of distribution in British waters see Wilson (1979a). In spite of this deep-water habitat, L. pertusa is well-known as a member of the British fauna and thus merits inclusion here.