Biodiversity & Conservation

Horse mussel - Modiolus modiolus - General information

Modiolus modiolus

Image Anon. - Horse mussel bed with hydroids and red seaweed, Linga Sound, Shetland. Image width ca 50 cm.
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Distribution map

Modiolus modiolus 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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Modiolus modiolus is not listed under any importance categories.

General information

Key Icon Researched by: Dr Harvey Tyler-Walters Text page icon Refereed by: This information is not refereed.

Taxonomy icon Taxonomy

Phylum Mollusca Snails, slugs, mussels, cockles, clams & squid
Class Bivalvia Clams, cockles, mussels, oysters, and scallops
Map icon Recorded distribution in Britain and Ireland Found off all British coasts. Extensive beds are most common on northern or western coasts but absent south of the Irish Sea and Humber estuary. Records in the southwest and English Channel are likely to be single individuals or juveniles.
Habitat information icon Habitat information Found part buried in soft sediments or coarse grounds or attached to hard substrata, forming clumps or extensive beds or reefs. May be found on the lower shore in rock pools or in laminarian holdfasts but more common subtidally to ca 280 m.
Text page icon Description The shell is solid, swollen, approximately oblong or irregularly triangular in shape, with blunt umbones. The shell is dark blue or purple in colour, however the perisostracum gives adults a glossy yellow or dark brown appearance. In young animals the shell appears bluish and the periostracum is extended into long, smooth spines. The shell bears clear growth lines, and a sculpture of fine concentric lines and ridges. The inside of the shell is white, with a wide pallial line, a large anterior adductor muscle scar and small posterior adductor muscle scar. Adults are usually more than 10cm in length, although very large specimens may reach up to 22cm.

This review can be cited as follows:

Dr Harvey Tyler-Walters 2007. Modiolus modiolus. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 19/06/2013]. Available from: <http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817>