Olivella biplicata (Sowerby, 1825)
Common name(s): Purple olive shell, Purple olivella
|Olivella biplicata, Dana Point, CA 2001|
|(Photo by: Dave Cowles, 2001)|
How to Distinguish from Similar Species: Olivella baetica is more narrow and is usually brown, plus is mostly subtidal and is rarely found on exposed beaches. O. biplicata generally has purple coloration on it, even when worn (picture)
Geographical Range: Vancouver Island to Bahia Magdalena, Baja California
Depth Range: Low intertidal to 50 m
Habitat: Sandy bottoms, lagoons, bays.
Biology/Natural History: Burrows in sand, leaving a plowed trail behind it (photo). The foot is wedge shaped to facilitate plowing (photo). While burrowing it raises its long siphon up through the sand as a snorkel. Found nearshore on fairly quiet, protected beaches and farther offshore on more exposed beaches. Predators include the seastars Pisaster brevispinus and Astropecten armatus, octopus, moon snails, and gulls. The snail digs or crawls rapidly or somersaults if touched by Pisaster brevispinus tube feet. Primarily found along the open coast rather than in protected waters such as Puget Sound. Most active at night, often move up and down the beach with the tide. Larger animals live higher on the beach than smaller ones do. May congregate in large clusters (photo). Probably omnivorous. Will eat kelp blades and live and dead animal material. May eat small detritus. Males find females by following their tracks, then glues himself temporarily to her shell. Mating takes up to 3 days. Egg capsules are about 0.5 mm, are deposited individually on small stones, shells, etc. Grow to 1.6 cm first year, 1-5 mm/year thereafter. Live 8-15 years. May be parasitized by trematode larvae (in the gonads--may castrate host). May contain high levels of heavy metals such as copper, lead, silver, cadmium, and zinc.
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Morris et al., 1980
This species is of special value to the Makah indian tribe at Neah Bay.
This individual (above and below) was found at Toleak Point, on the open Washington coast. The scale in millimeters, with centimeters marked.
Note that there are two folds on the columella, and that the white callus on the anterior (right) end is about 1/3 the total length of the shell.
|The following photos show Olivella biplicata actvity on sandy regions of Shi Shi Beach. All the photos can be enlarged for a closer look by clicking on them.|
|Ths is an aggregation of Olvella biplicata
seen in late July. There was a wide sandy area the individuals
could have occupied but nearly all the individuals were aggregated in a
this and a few other small areas near the zero tide line. The
photo was taken at daybreak in late July, 2008 by Dave Cowles.||Most
of the individuals in the aggregation at left were completely buried in
the sand as can be seen on the left and right in this photo. A
number of them, however, were incompletely buried as seen in the
center. The center individual is burying itself posterior
end-first in the sand, and is extending its inhalant siphon up toward
individual is crawling across the beach. Unlike the other photos
in this set, this one was taken in 2007, of an individual not in an aggregation. The individual
was buried in the sand at the end of the trail but I popped it out for
the photo. Photo by Dave Cowles at Shi Shi beach, near dawn in
early August 2007.||This individual appears to have
previously been in or at the burrow at the right which is still
occupied by another individual. Now it is crawling around among
the burrows on the left. This was not the only individual in the
aggregation that appeared to have been visiting other burrows.
Because of the tight aggregation of individuals and the evidence
of visiting burrows, I assume that this is a mating aggregation. |
member of the aggregation is crawling across the sand. Note the
plowlike configuration of the anterior foot, which would help the snail
to burrow through sand. Note also the white inhalant siphon,
which is extended forward, and the dark tentacle-like extension of the
mantle which is held across the top of the shell.||This individual member of the aggregation appears to be lying on its left side with its foot and mantle extended around the anterior and ventral end. Note how the inhalant siphon is extending back toward the nearby burrow. I wonder if this individual is preparing to dig into the sand next to the individual in the burrow.|