Description: This
species is cap-shaped
(limpet-like) with an apex
nearly as tall or taller than the shell is wide. The apex is
prominent
and usually arched (recurved),
beaklike. The periostracum
is dark brown. The inside contains a white shelf or septum
(as do
all slipper shells). In this species the shelf is on the
posterior
end, as is the recurved apex. The species grows to about 2.5
cm long
(usually smaller).
How to Distinguish from
Similar Species: This
species is the only one in this area with a very tall, arched,
beaklike,
recurved apex and a brown periostracum
Geographical Range: Queen
Charlotte Islands
(British Columbia) to Punta Santo Tomas, Baja California
Depth Range: Mid
to low intertidal
Habitat: Rocky
coast, mainly on Chlorostoma funebralis (black turban, formerly Tegula funebralis) shells
Biology/Natural
History: This filter-feeding
species specializes in living on Chlorostoma funebralis, Calliostoma
ligatum, and Searlesia dira
shells. It is a protandric
hermaphrodite. A newly settled individual is male.
As the individual
grows another (male) individual may settle on its shell, and the bottom
individual becomes female. This species broods its eggs,
which have
direct development. The eggs are kept in capsules under the
mother's
shell. When the young are ready for release the mother lifts
her
shell 1-3 mm above the substrate and pushes them out with her
head.
Newly liberated young are like small adults, 1.9 mm long.
They usually
fall off the Chlorostoma shell and grow to about 4 mm
before they find
another host. A related species, Crepidula fornicata,
is native
to the Atlantic but has been introduced to a few areas in the Northwest
with oysters.
References:
Dichotomous Keys:
Kozloff,
1987, 1996
Smith
and Carlton, 1975
General References:
Kozloff,
1993
Niesen,
1994
Scientific Articles:
General Notes and
Observations: Locations, abundances,
unusual behaviors, etc.:
Two male C. adunca on a female, all on a Tegula
funebralis.
Dave Cowles, San Simeon, CA May 2005
I have found large numbers of Crepidula adunca
shells within
kelp holdfasts on the open coast, such as at Shi Shi beach,
2007.
The shells had little periostracum on the outside and so had likely
been
dead for some time. The holdfasts had physically attached to
the
external surfaces of the shells so that, if the snails had been alive,
they would have been completely immobile. I am not sure
whether Crepidula
adunca also lives within kelp holdfasts or whether the
holdfasts somehow
had picked up and incorporated many of the shells. There were
many
other types of shells in the area but only a few species were present
in
the holdfasts so I suspect they were living there. I found no Chlorostoma funebralis shells in the holdfasts.
Another pair of Crepidula adunca on Chlorostoma funebralis, from Hole in the Wall (Rialto Beach) Jyly 2021. Photo by Dave Cowles
Authors and Editors of Page:
Dave Cowles (2004): Created original page
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