Species Account

Axinulus croulinensis (Jeffreys, 1847)

Thyasiroidea : Thyasiridae

Tebble name: Thyasira croulinensis (Jeffreys)
Smith & Heppell name: Axinulus croulinensis (Jeffreys, 1847)

To size: To 2.5mm. Shell Structure: Fragile. Equivalve: Equivalve. Equilateral: Equilateral. Tumidity: Inflated. Outline: Oval, higher than long; short anterior-dorsal margin distinct, horizontal; anterior margin curved; ventral margin evenly curved; posterior margin weakly biangulate. Contour: Umbos distinct; auricle low and indistinct. Posterior area a little flattened.

Sculpture: Of concentric lines only. Margin: Inner margin smooth. Ligament: Sunken on a short resilifer. Hinge: Hinge plate weak, teeth absent but plate slightly thickened beneath and anterior to beak. Pallial Musculature: Muscle scars obscure. Periostracum: Transparent. Colour: Shell white, often semi-transparent. Additional Characters: 1 demibranch.

Distribution & Ecology

Mostly found on the outer shelf and slope. In the northern North Sea is common from 85-220m. Appears to be absent from the shelf further south but present on the shelf edge and slope from 200-2000m. Is sporadically present in Scottish sea lochs in waters as shallow as 30m.
Payne & Allen (1991) give a depth range of 40-3861m and a pan-Atlantic distribution. Partially chemosymbiotic, partially suspension feeder. Gill with 1 demibranch, Dufour found few symbiotic bacteria. Is found in mud and muddy sand in a wide range of settings from shallow waters in Scottish sea lochs to bathyal depths on the slope.
Gill anatomy – Dufour, 2005
Gross anatomy – Payne & Allen, 1991

Depth Range
Continental Shelf (to 200m)
Continental Margin Zone (200 - 500m)
Bathyal (500 - 2000m)

Additional Information & Related Species


Listed are literature citing Axinulus croulinensis (Jeffreys, 1847). Reference containing the species Type Description is highlighted.

Dufour S C 2005. Gill anatomy and the evolution of symbiosis in the bivalve family Thyasiridae. Biological Bulletin. 208: 200-212.
Jeffreys J G 1847. Additional notices on British shells. Annals and magazine of Natural History. 20: 16-19.
Oliver P G & Killeen I J 2002. The Thyasiridae (Mollusca: bivalvia) of the British continental shelf and North Sea Oilfields. Studies in Marine Biodiversity and Systematics from the National Museum of Wales. BIOMOR Reports. 3: 1-73.
Payne C.M. & Allen J.A. 1991. The morphology of deep-sea Thyasiridae (Mollusca: Bivalvia) from the Atlantic Ocean. Philosophical Transactions of the Royal Society of London Series B. 334: 481-566.


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Record last modified: 17/05/2016