Biodiversity & Conservation

Green crenella - Musculus discors - General information

Musculus discors

Image Keith Hiscock - Musculus discors living in bryozoan turf collected from dead Eunicella verrucosa. Image width ca 3 cm.
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Distribution map

Musculus discors 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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Musculus discors 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 Common around most of the British Isles from Shetland to the Channel Isles.
Habitat information icon Habitat information Found in scattered, gregarious clumps growing epiphytically on the holdfasts of seaweeds and amongst faunal turfs from the lower intertidal to the circalittoral subtidal on most substrata. It occasionally forms extensive, dense aggregations covering upward facing rock surfaces.
Text page icon Description A small bivalve, usually up to 12 mm in length. The shell is brittle, equivalved but inequilateral and rhomboidal in outline. The beaks and umbones slightly raised and a short distance from the anterior end. The anterior and posterior portions of the shell bear different numbers of radiating ribs, while the middle region lacks ribs. Where the ribs meet the shell margin, the margin is crenulated but is smooth elsewhere. The shell is yellow to brownish in colour with a pale green to olive periostracum. The inside of the shell is pearly (nacreous) with a narrow pallial line and distinct anterior and posterior adductor scars. This genus is unusual in that the byssus threads used to fix it to the substratum are woven into a nest or cage, that may incorporate macroalgae (e.g., Fucus spp. and Laminaria spp.). This species lays its eggs in mucus strings that are retained within the byssal nest.

This review can be cited as follows:

Dr Harvey Tyler-Walters 2001. Musculus discors. Green crenella. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25/05/2013]. Available from: <http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3836>