Rock scallop, giant rock scallop, purple-hinged rock scallop • Crassodoma gigantea
{Crassodoma = big house}
Top left: rock scallop with blue branching seaweed and other organisms encrusting the shell. Photo by Nathaniel Glickman. Top right: Rock scallop among red sea urchins. Photo by Rosie Child. Centre and bottom: one valve of a rock scallop shell. Note the thickness of the shell, the extensive shell pitting on both inside and outside surfaces, and the purple stain near the hinge.
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Identification
The rock scallop has a thick round shell with a ribbed exterior that bears many spines. Two shell wings, located on either side of the hinge, may not be easily visible. The irregular shell texture is often obscured by plant and animal growths that encrust the shell. Additionally, the yellow boring sponge (Cliona californiana) and other invertebrates often infest rock scallop shells, leaving the shells riddled with holes. The scallop's interior is white while the mantle is orange and dotted with many small black eyes. Empty shells can be identified by a purple stain on the inside near the hinge. At 25 cm across the rock scallop is the second largest scallop in the world, and due to its thick shell it wins the title of heaviest. Click here for more photos.
Habitat & Range
The juvenile rock scallop is free swimming until it reaches a diameter of around 1 inch, at which point it cements one of its shell valves to rock or another hard surface in the intertidal and subtidal (to 80 m deep) of current-swept areas along exposed outer coasts. It may be found under boulders or in rock crevices. Its range extends from northern Alaska to northern Mexico.
Similar Species
Juveniles, which have orange to white shells and are not attached to rock, may be confused with pink scallops (Chlamys hastata and C. rubida). Adults cannot be easily confused as no other scallop species in the region cements itself to hard substrates.
Human Uses
The rock scallop is edible, and is a traditional food source of coastal First Nations groups; however due its slow-growing nature and relatively long life span (to 20 years or more) this species can be quickly depleted from an area.
iNaturalist
https://www.inaturalist.org/taxa/54526-Crassadoma-gigantea
The rock scallop has a thick round shell with a ribbed exterior that bears many spines. Two shell wings, located on either side of the hinge, may not be easily visible. The irregular shell texture is often obscured by plant and animal growths that encrust the shell. Additionally, the yellow boring sponge (Cliona californiana) and other invertebrates often infest rock scallop shells, leaving the shells riddled with holes. The scallop's interior is white while the mantle is orange and dotted with many small black eyes. Empty shells can be identified by a purple stain on the inside near the hinge. At 25 cm across the rock scallop is the second largest scallop in the world, and due to its thick shell it wins the title of heaviest. Click here for more photos.
Habitat & Range
The juvenile rock scallop is free swimming until it reaches a diameter of around 1 inch, at which point it cements one of its shell valves to rock or another hard surface in the intertidal and subtidal (to 80 m deep) of current-swept areas along exposed outer coasts. It may be found under boulders or in rock crevices. Its range extends from northern Alaska to northern Mexico.
Similar Species
Juveniles, which have orange to white shells and are not attached to rock, may be confused with pink scallops (Chlamys hastata and C. rubida). Adults cannot be easily confused as no other scallop species in the region cements itself to hard substrates.
Human Uses
The rock scallop is edible, and is a traditional food source of coastal First Nations groups; however due its slow-growing nature and relatively long life span (to 20 years or more) this species can be quickly depleted from an area.
iNaturalist
https://www.inaturalist.org/taxa/54526-Crassadoma-gigantea
References
Adams, M.J. Crassadoma gigantea (Purple hinged rock scallop). Beach Watchers. Washington State University. Accessed 18/12/2014.
Harbo, R. M. (1999). Whelks to whales: Coastal marine life of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P. 124.
Lamb, A., and Hanby, B. (2005). Marine Life of the Pacific Northwest [electronic version]. Madeira Park, BC: Harbour Publishing.
Cowles, D. (2005). Crassodoma gigantea (Gray, 1825). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 18/12/2014.
Authors and editors of page
Kelly Fretwell and Brian Starzomski (2014).
Adams, M.J. Crassadoma gigantea (Purple hinged rock scallop). Beach Watchers. Washington State University. Accessed 18/12/2014.
Harbo, R. M. (1999). Whelks to whales: Coastal marine life of the Pacific Northwest. Madeira Park, BC: Harbour Publishing. P. 124.
Lamb, A., and Hanby, B. (2005). Marine Life of the Pacific Northwest [electronic version]. Madeira Park, BC: Harbour Publishing.
Cowles, D. (2005). Crassodoma gigantea (Gray, 1825). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 18/12/2014.
Authors and editors of page
Kelly Fretwell and Brian Starzomski (2014).