Axinopsida orbiculata (G O Sars, 1878)
Thyasiroidea : Thyasiridae
To size: To 6mm in length. Shell Structure: Rather solid. Equivalve: Equivalve. Equilateral: Equilateral. Tumidity: Lenticular. Outline: Subcircular, posterior dorsal margin gently curved, anterior dorsal margin sunken; other margins broadly rounded. Contour: Lunule distinct; posterior area slightly flattened but not sulcate.
Sculpture: Smooth with growth lines. Ligament: External but sunken, extending 2/3 length of posterior dorsal margin. Hinge: RV with a large single cardinal peg, LV with a corresponding socket. Pallial Musculature: Pallial line entire, anterior adductor elongate but not separated from pallial line. Periostracum: Thin, yellowish. Colour: Shell white. Additional Characters: 2 demibranchs.
Distribution & Ecology
Common in glacial sediments in fjordic settings from shallow subtidal to a few hundered metres.
Ecology – Aitken & Fournier, 1993; Włodarska-Kowalczuk, 2007.
Deposit feeder, Gill with 2 demibranchs not modified for bacterial symbiosis (Dufour, 2005).
Continental Shelf (to 200m)
Continental Margin Zone (200 - 500m)
Bathyal (500 - 2000m)
Additional Information & Related Species
Thyasiroidea : Thyasiridae
Listed are literature citing Axinopsida orbiculata (G O Sars, 1878). Reference containing the species Type Description is highlighted.
Aitken A E & Fournier J 1993. Macrobenthic communities of Cambridge, McBeth and Itirbilung Fiords, Baffin Island, Northwest Territories, Canada. Arctic. 46: 60-71.
Dufour S C 2005. Gill anatomy and the evolution of symbiosis in the bivalve family Thyasiridae. Biological Bulletin. 208: 200-212.
Madsen FJ 1949. Marine bivalvia. The Zoology of Iceland. Vol 4 (63): 1-116.
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.
Sars G O 1878. Bidrag til kundskaben om Norges arktiske fauna: 1. Mollusca regionis Arcticae Norvegiae. Oversigt over de i Norges arktiske region forekommende bloddyr A W Brogger, Christiana. 466pp, 34pls.
Włodarska-Kowalczuk M 2007. Molluscs in Kongsfjorden (Spitsbergen, Svalbard): a species list and patterns of distribution and diversity. Polar Research. 26: 48-63.
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