Clinocardium nuttallii (Conrad, 1837) Common name(s): Heart cockle, Nuttall's cockle, basket cockle
Synonyms: Cardium orbis
Phylum Mollusca  Class Bivalvia   Subclass Heterodonta    Order Veneroida     Family Cardiidae
	Clinocardium nuttallii, 4 cm long and 4.2 cm high.
	(Photo by: Dave Cowles, July 2005)

How to Distinguish from Similar Species: Other cockles in the area have an area in the posterior quarter that has prominent concentric ridges as well as radial ribs, or are wider than high; and do not get larger than about 4 cm.  The littleneck clam Protothaca staminea has much less prominent radial ribs and the ventral margin does not undulate.

Geographical Range: Bering Sea to San Diego, CA; Japan; very common in Rosario area.

Depth Range: Low intertidal to 200 m; mostly intertidal and shallow subtidal

Habitat: Fine sediment, especially muddy fine sand (not plain mud).  Lies barely buried in the sediment.  Often in eelgrass beds.

Biology/Natural History: Growth rings may be prominent, especially in the northern parts of its range, as this species nearly ceases feeding in winter.  Yearly growth lines are much less prominent farther south, but tidal cycle growth lines can often be seen.  Mantle margin has tiny tentacles with tiny eyes.  Pumps 2.51 liters of water per hour per gram body weight.  Predators include Pycnopodia helianthoides, Pisaster brevispinus, Cancer magister, and gulls.  The cockle has a strong escape response to Pycnopodia--rapidly extending its foot and jumping away (movie).  May be a source of paralytic shellfish poisoning (PSP) for humans.  A simultaneous hermaphrodite (has both functional male and female gonads at the same time).  In Puget Sound they mature in their second year and spawn in July and August.  Live 15-19 years in Alaska.  May contain small pea crabs such as Pinnixa faba inside the mantle cavity.

References:

General References:
Brusca and Brusca, 1978
Harbo, 1997
Harbo, 1999
Johnson and Snook (1955) (as Cardium corbis)
Kozloff, 1993
McConnaughey and McConnaughey, 1985
Morris, 1966
Morris et al., 1980
Niesen, 1994
Niesen, 1997
O'Clair and O'Clair, 1998
Ricketts et al., 1985
Sept, 1999

Scientific Articles:

We find this species to be the most commonly found bivalve in western Padilla Bay, along the east side of March Point.

Clinocardium nuttallii shells have various brown bands and blotches on the valves.

Cockles have two adductor muscle scars of nearly equal size, and cardinal and lateral teeth.  Photo of Clinocardium nuttallii shell by Dave Cowles, July 2005

The same photo as above, with many of the features labeled.

The radial ribs interlock as undulations along the ventral margin, which likely strengthens the shell by making the two valves difficult to twist apart.  I am holding the two valves slightly apart here to clearly show the gap--in full closure they interlock tightly.  Photo by Dave Cowles, July 2005

A side view shows why this cockle is called the heart cockle.  Photo by Dave Cowles, July 2005

This dorsal view shows the umbones and external hinge. Photo by Dave Cowles, June 2020

Clinocardium nuttallii has short siphons, mainly white.  Note that the incurrent siphon is larger than the excurrent siphon, as is common in many bivalves.
Photo by Dave Cowles, July 2007

This species jumps rapidly by extending its foot when it senses predatory seastars such as  Pycnopodia helianthoides or Pisaster ochraceus.  Click here for a movie of the jump near Pycnopodia.