Searlesia dira (Reeve, 1846)
Common name(s): Dire whelk, Spindle shell, Spindle whelk
|Synonyms: Lirabuccinium dirum, Kelletia dira|
|Searlesia dira from Sares Head. Total length 3.9 cm|
|(Photo by: Dave Cowles July 2005)|
How to Distinguish from Similar Species:_Acanthina spirata also has dark spiral ridges but is less elongated and has a distinct tooth on the outer lip of the aperture; Nucella canaliculata has similar spiral ridges but is less elongated and the whorls are separated by a deep groove.
Geographical Range: Chirikof Island, Alaska, to Monterey, CA. Abundant in British Columbia, Washington and Oregon; spoty in California. Said to be the commonest littoral snail in rocky shores of N. British Columbia.
Depth Range: Mostly intertidal (but also on Cobb Seamount at 35 m depth)
Habitat: Rocky shores; lower edges of rocks in gravel or mud in bays
Biology/Natural History: Predatory or mainly scavenging. Prey include Littorina, limpets, barnacles, chitons, worms, and other animals; specializing in finding and eating injured animals which it often eats without drilling into the shell of (it does not seem to be able to drill into shells). Readily eats carrion such as dead crabs or fishes. Proboscis can extend the length of the shell. May extend proboscis to digest worms in their tubes, or to feed on prey that are being eaten by the everted stomach of Pisaster ochraceous. Predators include the seastars Orthasterias keohleri and Leptasterias hexactis, and Barrow's Goldeneyes (Bucephala islandica). Hatchling snails are eaten by hermit crabs Pagurus hirsutiusculus and by purple shore crabs Hemigrapsus nudus. The slipper snail Crepidula adunca may be found living on the shell. In muddy bays, this shell is a favorite of the hermit crab Pagurus granosimanus (but not of P. hirsutiusculus). Females deposit low, convex egg capsules in clusters on rock walls of crevices from September to May. Most of the eggs in a cluster ("nurse eggs") do not develop fully and are used as food by the veliger larvae that do develop. Do not migrate with the tides. Larger individuals are more common in the lower intertidal. May live 15 years.
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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
This indivudual was in a crevice on Swirl Rocks, July 2007.
Here is an unusual yellow individual found subtidally near Rosario in 2006.
Except for the yellow color this shell keys to Searlesia dira. Several malacologists at an American Malacological Society meeting confirmed that it is indeed Searlesia dira.
The aperture of the yellow individual.
Although in most specimens the axial ribs do not extend onto the body whorl, the ribs do in fact extend onto at least the upper half of the body whorl in tiny specimens as can be seen in this individual.
|The tiny Searlesia dira individual below was only 7 mm long. Photos by Dave Cowles, August 2009|