Saw-toothed Heart Cockle
Fragum fragum
Shell medium, inequilateral, shell notably higher than long, sharply pointed ventrally with strong keel. Posterior flattened and narrow, steep. Sculpture of strong radial ribs circa 32 range 27-37 (WAM material), surfaces broad and flat. Ribs flattened with close set transverse curved scales, becoming coarser anteriorly. Lateral teeth extremely inequidistant from cardinals. Shell cream, rugae or nodules on ribs often yellowish. Interior color white, but with often yellow-orange flares radiating from umbonal cavity.
Morphology
Fragum fragum is a photosymbiotic species intermediate between Corculum and Fragum unedo. Semi-transparent posterior areas (pigment and windows) exist to allow light penetration. As well, siphonal tentacles are exposed to light on posterior shell surface and contain photosymbionts.
Evolution
This is the type species of the genus Fragum. Kirkendale (2009) has shown (and others have confirmed e.g. Herrera et al. 2015) that Fragum is paraphyletic and includes Corculum and Lunulicardia, the two other wholly photosymbiotic lineages of cardiids.The phylogeny of members of the Fraginae subfamily is in a state of flux and the taxonomy of the group is in need of attention.
Behaviour
All cockles or cardiids have short siphons. Because of this morphological constraint, infaunal cardiids live close to the sediment water interface in order to filter water. This could be considered a preadaptation for a photosymbiotic lifestyle, as it also facilitates optimal light penetration into the soft tissues in shell interior where photosymbionts are housed.
Method of reproduction
Broadcast spawner.
Habitat
Marine
Intertidal to shallow subtidal insandy areas. Generally in sheltered areas. In reefal habitats can be found from sandy areas through to seagrass bed perimeters and rubble.
Distribution
QLD, NT and WA in Australia, but widely distributed in the Indo-west Pacific.
Life Cycle
Short lived veliger larvae.
Kingdom: | Animalia |
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Phylum: | Mollusca |
Class: | Bivalvia |
Subclass: | Heterodonta |
Superorder: | Imparidentia |
Order: | Cardiida |
Superfamily: | Cardioidea |
Family: | Cardiidae |
Subfamily: | Fraginae |
Genus: | Fragum |
Species: | fragum |
Name Published Year: | 1758 |
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Rank: | species |
Scientific Name Authorship: | Linnaeus |
Commercial Impact: | None |
Conservation Assessment: | Least Concern |
Cite this page
Western Australian Museum Collections https://museum.wa.gov.au/online-collections/names/fragum-fragum
Accessed 30 Aug 2023
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