This habitat is no longer an MCZ Feature of Conservation
Importance. Please refer to the MCZ FOCI Review 2016
File shell beds
The file shell is a very distinctive
bivalve. The two halves of its shell do not close completely,
and a thick fringe of bright orange or red tentacles extends
File shells are usually found on sand or
gravel seabeds. They often use their sticky byssus thread
‘beards’ to form nests of debris, mud and seaweed fragments, within
which the animals are completely hidden. This is thought to
be a means of defence: a file shell cannot pull in its tentacles,
which are vulnerable to being nipped off by passing
predators. In tide-swept, shallow inlets and bays, where file
shells occur in large numbers, the nests can join up to form a
reef, which can extend to several hectares in size.
In shallow water, kelp seaweeds may settle
onto the file shell beds. Maerl and horse mussels may also
form part of the reef. Other animals that find food and
shelter here include crabs, starfish, young cod and
File shell beds form a surface for
attachment and a refuge in an otherwise featureless seascape.
Where file shell beds have been lost, the seaweeds and young fish
have also disappeared, illustrating the importance of these beds as
a key feature in the local environment.
Scallop dredging and trawling are main
threats to file shell beds. They have also been destroyed by
pollution from the anti-fouling paints used to stop marine
creatures attaching to ships’ hulls and underwater structures.
For the official habitat definition please
see the documents listed below.
File shells are found on the west and
south-west coasts of the UK, and are most common off western
Scotland. The European range extends south to Mediterranean and
Canary Isles. Large reefs of file shells are scarce, however,
and are usually found in the mouths of sea lochs. They have only
been recorded from the west coast of Scotland and from Donegal.
This is a UK BAP Priority Habitat (BAP habitats
are now Habitats of Principal Importance/Priority
UK Biodiversity Action Plan; Priority Habitat Descriptions. BRIG
(ed. Ant Maddock) 2008 (updated December 2011)
Life Information Network - Limaria hians
World Register of Marine Species - Limaria hians
Marine Species Identification Portal - Limaria
Conchological Society of Great Britain and Ireland - Limaria
Marine Life Information Network - Limaria hians beds in
tide-swept sublittoral muddy mixed sediment
JNCC - UK BAP Priority
Species and Habitats
JNCC EUNIS habitat correlations table