Biodiversity & Conservation

Phosphorescent sea pen - Pennatula phosphorea

Pennatula phosphorea

Image Mark Davies - Pennatula phosphorea and Turritella communis in muddy sediment. Image width ca 80 cm.
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Distribution map

Pennatula phosphorea recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

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Pennatula phosphorea is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Cnidaria Sea anemones, corals, sea firs & jellyfish
Class Octocorallia
Authority Linnaeus, 1758
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland Recorded in Scottish west coast sea lochs and the Shetlands. It has also been recorded in west Scotland, the Irish Sea including off the Welsh coast and is frequent in the North Sea, but not in southern England.
Habitat information icon Habitat information Found in sandy and muddy substrata at depths of 10m-100 m.
Text page icon Description Colonies are stout and fleshy and up to 40 cm long. The seapen is composed of a basal peduncle embedded in the substratum, from which arise leaf-like branches. Fused polyps form large triangular 'leaves' in alternate opposing lateral rows. The back of the peduncle is covered in inhalent polyps (siphonozooids). The flesh is translucent, yellowish or pale pink with white polyps. The colony may also be a deep reddish-pink owing to the presence of red skeletal plates in the tissue. The central axis of the colony is often bent-over at the tip like a shepherds crook.
Identifying features
  • Feeding polyps separate.
  • Upper regions of the body with red/pink colouration.
  • The central axis of the colony is often bent over at the tip like a shepherd's crook.
  • Flesh is translucent, yellowish or pale pink with white polyps.
Additional information icon Additional information Pennatula phosphorea luminesces in a blue/green colour when stimulated. The luminous waves proceed in either direction, with a measurable velocity, to the extremities of the animal. Light is emitted by the polyps, which are believed to be connected by a nerve net. There is a gradual increase in light intensity with increasing number of disturbances as a result of facilitation (Nicol, 1958). Pennatula phosphorea contracts when disturbed, and swells by up-taking water when unperturbed (Nicol, 1958). It is also capable of withdrawing into a tube below the mud surface (Mackie, 1998). Extracts from this species have been found to show narcotic and anorectic properties, acting as feeding deterrents for the octocoral's main predator the Dover sole, Solea solea (Mackie, 1998). They have stinging organelles like most sea anemones and all cnidarians, which are contained in polyps along the branches off the long peduncle.

This review can be cited as follows:

Hugh Jones 2008. Pennatula phosphorea. Phosphorescent sea pen. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 04/02/2012]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=4068>