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Macoma nasuta

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Macoma nasuta
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Cardiida
Family: Tellinidae
Genus: Macoma
M. nasuta
Binomial name
Macoma nasuta
(Conrad, 1837)

Macoma nasuta, commonly known as the bent-nosed clam, is a species of bivalve found along the Pacific Ocean coast of North America. It is about 6 cm (2.4 in) long.[1] It is often found buried in sands of 10–20 cm (3.9–7.9 in) in depth.[1] This rounded clam has no radial ribs. Archaeological data supports the use of this species by Native Americans such as the Chumash peoples of central California.[2]



Macoma nasuta is commonly known as the bent-nosed clam or bent-nose Macoma.[3] It is commonly misidentified as either Macoma tersa or Macoma kelseyi.[3]



The hinge plate is without lateral teeth and the length of shell much less than twice the height. Posterior portions of both valves distinctly bent to the right with the siphons distinctly separated (as they are in all Macoma) and have a distinct orange pigmentation. The periostracum is usually very prominent and the shell has a dirty brown wrinkled look to it, especially near the margin.[4]

Distinguishing characteristics


Valves bent rather sharply to the right at the posterior end, orange coloration of its siphons and periostracum is usually very prominent.[3]



Common in intertidal and subtidal (50 m) zones; Prefers mud to muddy sand substrates situated in quiet waters and can burrow up to 40 cm beneath the surface sediment. M. nasuta and M. secta are geographically sympatric species and both are the characteristic species of Macoma on the west coast of North America.[5]



Found in the neritic provinces of the eastern Pacific Ocean from Kodiak Island, Alaska, to Cabo San Lucas, Baja California.[6]

Feeding and digestion


Found to feed off the top millimeter of sediment by using a boring motion with the tip of its siphon into the sediment or by using a rotating motion similar to Scrobicularia plana.[7] New sediment is found by moving the siphon into virgin sediment but the clams have also been observed to consume their pseudofeces and feces. It is assumed that the siphon tip is unselective in the particles it intakes.[8]

Non-specific nematodes have been found in the stomach in all stages of digestion from live to empty cuticles. The small (about 500 μm) bivalve Transenella tantilla has also been found living in the stomach. The relationship with both nematodes and T. tantilla is uncertain.[8]

The exhalant siphon is kept below the sediment surface (about 1 cm). The gut clearance time for inert particles of M. nasuta ranges from 1 to 9 hours with smaller particles and diatoms believed to remain longer than other particles ingested due to their disproportionably high presence in the stomach during dissections.[8]

Bioaccumulation of toxins


Due to their feeding behavior of deposit feeding, M. nasuta have been found to have high levels of DDT and PCBs.[9]



M. nasuta is a dioecious (probably gonochoristic) species that spawns in early summer.[6][10]

Natural history


There is archaeological data to support the use of this species by Native Americans such as the Chumash peoples of central California.[2]



Shore birds, Lewis' Moon Snail: Polinices lewisii, Starfish: Pisaster spp., Crabs: Cancer productus, Metacarcinus gracilis, Metacarcinus magister.[11]

Known parasites



  1. ^ a b Desmond, Julie S.; West, Janelle M.; Williams, Gregory D. (2001). "Appendix 5: Ecological and life history characteristics of common southern California salt marsh invertebrate species". In Zedler, Joy B. (ed.). Handbook for restoring tidal wetlands. Boca Raton, Florida: CRC Press. p. 403. ISBN 9781420036619.
  2. ^ a b C. Michael Hogan, Los Osos Back Bay, The Megalithic Portal, ed. Andy Burnham (January, 2008)
  3. ^ a b c Dave Cowles (2005). "Macoma (Heteromacoma) nasuta (Conrad, 1837)". Walla Walla University. Archived from the original on 2010-06-02. Retrieved 2010-07-31.
  4. ^ KOZLOFF, E. 1996. Marine invertebrates of the Pacific Northwest, Univ. Wash. Press ISBN 0-295-97562-8
  5. ^ Sept, J. Duane (1999). The beachcomber's guide to seashore life in the Pacific Northwest. Madeira Park, B.C.: Harbour Pub. ISBN 9781550172041.
  6. ^ a b Rae, John Gibson III (August 1978). "Reproduction in two sympatric species of Macoma (Bivalvia)". The Biological Bulletin. 155 (1): 207–219. doi:10.2307/1540876. JSTOR 1540876.
  7. ^ Hughes, Roger N. (11 May 2009). "A study of feeding in Scrobicularia plana". Journal of the Marine Biological Association of the United Kingdom. 49 (3): 805–823. doi:10.1017/S0025315400037309. S2CID 86570453.
  8. ^ a b c Hylleberg, J.; Gallucci, V. F. (1975). "Selectivity in feeding by the deposit-feeding bivalve Macoma nasuta". Marine Biology. 32 (2): 167–178. doi:10.1007/BF00388509. S2CID 84097681.
  9. ^ Boese, Bruce L.; Lee, Henry; Echols, Scott (July 1997). "Evaluation of a first-order model for the prediction of the bioaccumulation of PCBS and DDT from sediment into the marine deposit-feeding clam". Environmental Toxicology and Chemistry. 16 (7): 1545–1553. doi:10.1002/etc.5620160731. S2CID 84726449.
  10. ^ Bivalves of The Evergreen State College Campus
  11. ^ Kozloff, Eugene N. (1993). Seashore life of the northern Pacific coast: an illustrated guide to northern California, Oregon, Washington, and British Columbia. Seattle: University of Washington Press. ISBN 9780295960845.
  12. ^ Schell, Stewart C. (October 1986). "Graffilla pugetensis n. sp. (order Neorhabdocoela: Graffillidae), a parasite in the pericardial cavity of the bent-nose clam, Macoma nasuta (Conrad, 1837)". The Journal of Parasitology. 72 (5): 748–754. doi:10.2307/3281468. JSTOR 3281468.
  13. ^ DeMartini, John D.; Pratt, Ivan (February 1964). "The life cycle of Telolecithus pugetensis Lloyd and Guberlet, 1932 (Trematoda: Monorchidae)". The Journal of Parasitology. 50 (1): 101–105. doi:10.2307/3276040. JSTOR 3276040. PMID 14125150.