Biodiversity & Conservation

Philine aperta and Virgularia mirabilis in soft stable infralittoral mud



Image Rohan Holt - Dense Virgularia and Sagartiogeton. Image with ca XX cm.
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Distribution map

SS.SMu.IFiMu.PhiVir recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Text page icon Habitat description

Map icon Distribution of biotope in Britain and Ireland In the UK this biotope is almost confined to the most sheltered basins of certain sea lochs, with one further example known from Portland Harbour in southern England.
National importance Uncommon

Text page icon Description of biotope

For a full description of this biotope including characterizing species, distribution, survey information and references visit JNCC

Physically very stable muds with a high proportion of fine material (greater than 80 %) may contain the sea pen Virgularia mirabilis. These muds typically occur in shallow water to about 12-15 m where significant seasonal variation in temperature is presumed to occur. This habitat is restricted to the most sheltered basins in, for example, sea lochs. Although most records suggest full salinity conditions are prevalent, some sites may be subject to variable salinity. The opisthobranch Philine aperta is the most characteristic species of this habitat, occurring in high densities at many sites. The sea pen Virgularia mirabilis, a species found more widely in muddy sediments, appears to reach its highest densities in this shallow mud. Other conspicuous species found in this shallow muddy habitat include Cerianthus lloydii, Sagartiogeton spp., Ascidiella aspersa and Myxicola infundibulum. Amphiura chiajei and Amphiura filiformis may also be present at some sites. Burrowing crustacean megafauna, characteristic of deeper mud, are rare or absent from this shallow sediment. Of these burrowers Nephrops norvegicus may sometimes be recorded. The bivalves Nucula sp., Thyasira flexuosa and Corbula gibba may be other conspicuous infaunal species. The sediment may be covered by a diatom film. In the south of Great Britain, the polychaete Sternaspis scutata is also characteristic of this biotope. This polychaete is rare in Great Britain (Sanderson 1996). Indeed, this southern variant of the biotope is very restricted in the UK to Portland Harbour but is known to occur further south in the Gulf of Gascony and the Mediterranean (Glemarec 1973; Dauvin et al. 1994). Similar but deeper more stable muds to IMU.PhiVir are characterized by burrowing megafauna (CMU.SpMeg). IMU.PhiVir has a lot of similarity with CMU.BriAchi, possibly differing on account of low disturbance or linkage with enriched overlying waters, however, these hypotheses are untested. IMU.PhiVir may also be closely allied to CMS.AbrNucCor, showing some of the infaunal elements of this biotope. (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

Additional information icon Additional information

This review can be cited as follows:

Hill, J.M. & Wilson, E. 2005. Philine aperta and Virgularia mirabilis in soft stable infralittoral mud. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25/11/2015]. Available from: <>