Macoma (Heteromacoma) nasuta (Conrad, 1837)
Common name(s): Bent-nosed clam, Bent-nose Macoma
|Synonyms: Macoma tersa, Macoma kelseyi|
|Macoma nasuta from Padilla Bay, WA|
|(Photo by: Dave Cowles, July 2005)|
How to Distinguish from Similar Species: This is the only clam in this area that has the posterior ends of the valves bent to the right.
Geographical Range: Kodiak Island, Alaska to Cabo San Lucas, Baja California, Mexico
Depth Range: Low intertidal to 50 m
Habitat: Buried in mud flats; also found in gravel, sand, or muddy clay
Biology/Natural History: This common clam lies on its left side instead of vertically, at a depth of 10-20 cm. It rocks back and forth while digging. The siphons extend out the right side and up to the surface, which are well accomodated by the twist to the right of the shell. The siphons are used to suck debris from the surface of the sediment like a vacuum cleaner. The clams digest mainly diatoms and some flagellates from the sediments. They ingest large quantities of sediment but reject 97% of it, producing copious pseudofeces (photo). Hinton says the clam moves to another location when the sediment in an area has been thoroughly picked over. Predators include the moon snail Polinices lewisii. The clam was an important food of the coastal Indian tribes and to Chinese immigrants in San Francisco but is little used commercially today because of the debris that is usually in the gut. This species is very hardy and can be found in areas that have very poor circulation, and can live in very soft, silty mud. The pea crab Pinnixa littoralis or P. faba may live in the mantle cavity, as may the Nemertean worm Malacobdella grossa. The species spawns in early summer in Oregon.
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Brusca and Brusca, 1978
Johnson and Snook, 1955
McConnaughey and McConnaughey, 1985
Morris et al., 1980
O'Clair and O'Clair, 1998
Ricketts et al., 1985
The posterior end of the shell (left in the photo above) is bent to the right. Many individuals are bent more than this one is. Photo by Dave Cowles, July 2005
This species has long siphons which it can extend from the posterior end of the shell and up through several cm of sediment to the surface.
They look creamy white when extended but look more orange when they are retracted.
This species sucks in sediment, digests out some diatoms and flagellates, and rejects the majority of the sediment leading to copious production of pseudofeces, as seen in the photo.
Photo by Dave Cowles, August 2005