Venerupis philippinarum (A. Adams & Reeve, 1850) Common name(s): Manila clam, Japanese littleneck clam
Synonyms:  Tapes japonica, Tapes philippinarum, Tapes semidecussata, Protothaca semidecussata, Ruditapes philippinarum, Paphia sp..
Phylum Mollusca  Class Bivalvia   Order Veneroida    Family Veneridae
	Venerupis philippinarum from a local grocery store
	(Photo by: Dave Cowles, Jan 2007)

How to Distinguish from Similar Species:  Butter clams Saxidomus gigantea have only concentric sculpture.  Native littleneck clams Leukoma staminea are found in similar habitat and look similar but are as high as they are long, their ridges are less prominent, their siphons are fused all the way to the tips, and the inner ventral margin of the shell is finely serrated. These other species do not have purple markings inside the shell.  Another introduced species, Nuttallia obscurata, has purple markings inside the shell but the light brown periostracum is smooth and shiny.

Geographical Range:   Asia, Central BC to southern CA.

Depth Range:  High intertidal

Habitat:  Sand, mud, or gravel in the high intertidal zone.  May occasionally be attached to a stone by a byssus.

Biology/Natural History:  The siphon of this clam is not long (even though it has a well-developed pallial notch) and the clam buries only to 10 cm depth.  This clam is introduced from Asia.  It was first accidentally introduced into British Columbia in 1936 along with Pacific Oyster spat.  It has now become well established and is one of the main species of clam harvested along the coast of Washington and British Columbia.  Moon snails Polinices lewisii don't often attack this species because the species lives so high in the intertidal.  Breeds in the summer.  May contain pea crab symbionts Pinnixia faba or P. littoralis.  Tolarates salinity as low as 1/3 seawater.  May live 14 years.  May contain red tide toxins.

Dudas et al. (2005) found that the common local cancer crabs Metacarcinus magister (Dungeness crab) and Cancer productus (red rock crab) preferred the thin-shelled introduced varnish clam Nuttallia obscurata to the thicker-shelled clams Leukoma staminea and Venerupis philippinarum if access to all was equally easy.  However, Nuttallia obscurata typically lives deeper in the sediment than do Leukoma staminea or Venerupis philippinarum.  If they had to dig for them, Metacarcinus magister still ate more Nuttallia obscurata than it did of the other clam species, but C. productus' preference switched to Leukoma staminea and Venerupis philippinarum.

References:

General References:
  Harbo, 1997
  Harbo, 1999
  Kozloff, 1993 (as Tapes japonica)
  McConnaughey and McConnaughey, 1985 (as Tapes japonica)
  Morris, 1966 (as Tapes japonica)
  Morris et al., 1980
  Niesen, 1997 (as Tapes japonica)
  Ricketts et al., 1985 (as Tapes japonica)
 

Scientific Articles:
Dudas, Sarah E., Iain J. McGaw, and John F. Dower, 2005.  Selective crab predation on native and introduced bivalves in British Columbia.  Journal of Experimental Marine Biology and Ecology 325:1 pp 8-17

Ruesink, Jennifer L., B.E. Feist, C.J. Harvey, J.S. Hong, A.C. Trimble, and L.M. Wisehart, 2006.  Changes in productivity associated with four introduced species: ecosystem transformation of a 'pristine' estuary.  Marine Ecology Progress Series 311: pp 203-215. doi 10.3354/meps311203

Web sites:
  Washington Dept of Fish and Wildlife clam page

As is characteristic of members of Family Veneridae, this species has three well-developed hinge teeth in each valve.

The inside of the shell often has a purplish and/or a yellow coloration.  Note the distinct pallial line and pallial sinus.

Venerupis philippinarum has siphons which are dark but split into two distinct tubes at the end.  This can help distinguish living individuals from the littleneck clam, Protothaca staminea.
 

Some Venerupis philippinarum have only yellow and no purple inside.  This clam was from a package of live clams labeled as a product of Vietnam, and none of the clams in the package had a purple stain.  Notice the brownish radial streaks on the exterior of the shell.