Species Account

Idas simpsoni (Marshall, 1900)

Mytiloidea : Mytilidae

Tebble name: Adula simpsoni (Marshall)
Smith & Heppell name: Adipicola simpsoni (Marshall, 1900)

To size: To 40mm. Shell Structure: Thin. Equivalve: Equivalve. Equilateral: Inequilateral beaks at about 1/5 of shell length from anterior. Tumidity: A little inflated, umbos low but shell expansion greatest behind umbos. Outline: Submodioliform, elongate, with anterior distinctly more narrow than posterior; dorsal and ventral margins of about equal length, ventral subparallel to dorsal; ventral margin long slightly to distinctly incurved, dorsal margin gently curved, anterior dorsal margin sloping downwards making rounded anterior projecting, posterior broadly curved. Contour: Posterior angle distinct but rounded; median area a little depressed.

Sculpture: Smooth with a few growth lines, larger shells with a few radial lines on the median depression. Margin: Inner margin smooth. Ligament: Large, on a wide sunken, resilifer behind the beaks extending about 2/3 the length of the posterior dorsal margin. Hinge: Hinge plate narrow apparently smooth in large shells but in smaller shells with a few small dysodont teeth behind the ligament and 1-3 irregular crenulae below the beaks. Pallial Musculature: Anterior adductor scar only a little smaller than posterior, this with a small dorsal extension (byssus retractor scar). Periostracum: Persistent, glossy golden yellow to olive-brown in larger shells. Colour: White.

Distribution & Ecology

Attached to whale falls and therefore of sporadic discovery, likely to be found across the majority of study area. Also discovered in large numbers on diesel contaminated mud under oil rigs in the northern North Sea but no longer present.

Depth Range
Continental Shelf (to 200m)

Additional Information & Related Species


Listed are literature citing Idas simpsoni (Marshall, 1900). Reference containing the species Type Description is highlighted.

Bolotin J., Hrs-Brenko M., Tutman P., Glavic N., Kozul V., Skaramuca B., Lucic D. & Dulcic J. 2005. First record of Idas simpsoni (Mollusca: Bivalvia: Mytilidae) in the Adriatic Sea. Journal of the Marine Biological Association of the United Kingdom. 85: 977-978.
Marshall J T 1900. On a British species of Myrina, with a note on the genus Idas. Journal of Malacology. 7: 167-170.
Oliver PG & Holmes AM 2009. Idas lamellosus Verrill, 1881 (Bivalvia: Mytiloidea) a woodfall mussel new to the fauna of the northeast Atlantic. Journal of Conchology. 39 (6): 705-708.
Southward E C 2008. The Morphology of bacterial symbioses in the gills of mussels of the genera Adipola and Idas (Bivalvia: Mytilidae). Journal of Shellfish Research. 27(1): 139-146.
Warén A 1991. New and little known Mollusca from Iceland and Scandinavia. Sarsia. 76: 53-124.
Warén A. & Carrozza F. 1990. Idas ghisotti sp.n., a new mytilid bivalve associated with sunken wood in the Mediterranean. Bollettino Malacologico. 26: 19-24.


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Record last modified: 22/03/2016