Astarte sulcata (da Costa, 1778)Crassatelloidea : Astartidae
To size: To 30mm. Shell Structure: Solid. Equivalve: Equivalve. Equilateral: Relatively inequilateral, the beaks lie approximately 35% of dorsal margin length from anterior. Tumidity: Slightly tumid. Outline: Sub-ovate to rounded quadrangular, height of shell approximately 90% of the height. Posterior dorsal margin long, gently sloping, very slightly convex to almost straight; anterior dorsal margin more steeply sloping and conspicuously concave; anterior end slightly rounded; posterior end truncated/bluntly rounded; ventral margin gently rounded; lunule distinct, sunken, elongate heart-shaped with well defined, raised edges; escutcheon distinct, lanceolate, with very well defined raised edges. Beaks prosogyrous.
Sculpture: Broad, concentric, strap-like ridges, ranging in number from 25 to over 40 in adult individuals. Margin: Initially smooth, becoming crenulate in older shells. Size at which crenulations appear varies between populations. Ligament: Broad, distinct but not prominently raised, runs for approximately one third the length of the escutcheon. Hinge: Heterodont: Robust hinge plate; right valve with 2 solid, blunt cardinal teeth, the posterior tooth is thin and inconspicuous and the anterior tooth is broad; left valve with 3 blunt cardinal teeth, the 2 anterior teeth are relatively broad and solid whereas the posterior cardinal is very thin and inconspicuous. The posterior part of the right valve has a thickened ridge similar to a lateral tooth. Pallial Musculature: Entire. Periostracum: Ranges from yellowy brown to dark brown, almost black. Dull surface texture with a fine wavy linear pattern. Colour: White.
Distribution & Ecology
Occurs all around Britain and Ireland, but rare or absent in the southern North Sea and eastern English Channel
Lives in a range of usually silty and muddy sands and gravels from the near sub-littoral towards the shelf edge and on the very upper slope, depth range 5 to 250m or more.
Continental Shelf (to 200m)
Continental Margin Zone (200 - 500m)
Juveniles & Similar Species
Key Features & Similar Species
Given the considerable variation in outline we consider the periostracum to be the most conclusive character for recognising A. sulcata. The pattern is of fine wavy lines and is not netted (A. elliptica) or punctate (A. montagui and A. crenata group).
Within our study area there are many described varieties of A. sulcata. These varieties are based on both outline and number of ribs. We have illustrated many specimens to show variation with the primary differences depending on the gradient in outline from subovate to rounded subtrigonal. The more rounded forms appear to become more frequent in northern waters and have been assigned to var. scotica. Deeper water shells are also often more rounded or sometimes quadrate and often smaller. They may have smooth or crenulate inner margins. However, all shells that we assign to A. sulcata have a periostracum with a wavy linear pattern. This pattern is not shared with A. elliptica or the A. crenata group.
The presence of a crenulated margin is not a reliable character. Crenulations are not present in juvenile shells and the size at which they appear varies between populations. We suspect that their appearance is age related and not size related and is often associated with a thickening of the margin.
Listed are literature citing Astarte sulcata (da Costa, 1778). Reference containing the species Type Description is highlighted.
da Costa E M 1778. Historia Naturalis Testaceorum Britanniae London: Millan, White, Elmsley & Robson. 254pp, 17pls.
Høpner Petersen G. 2001. Studies on some Arctic and Baltic Astarte species (Bivalvia, Mollusca). Bioscience. 52: 1-71.
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