mitra is a
sea snail, specifically a limpet. Its body has a soft,
which secretes a hard, cone-shaped shell. This is an entirely
limpet, but it is often encrusted by a coralline red alga.
is thick, taller than other local limpets, and the apex is only
anterior to the center. The surface may be
fine concentric growth lines and radial striations. Length to
cm, height to 3 cm. This limpet is easily identified by its
and height. Note: Formerly nearly all our
were classified in family Acmaeidae. Now most of the others
been moved to family Lottiidae, and this is the only species left in
White-Cap Limpet, Dunce-cap limpet,
Bishop's cap limpet,
Chinese hat limpet
|Acmaea mitra shell found at
Rosario. The true shell color
(white) shows through, and the shell of this individual is partly
by a burrowing species.
|Photo by: Ryan Lunsford
How to Distinguish from
Similar Species: Acmaea
mitra is the only all white limpet, and is much taller and
like a miter or short dunce's cap than are other limpets.
Alaska to Baja California.
Depth Range: Low
intertidal and mostly
mitra can be found
whereever red coralline algae is present.
mitra is known by its tall shell, which can reach a height of
and a length of 35 mm. The scientific name means "pointed
This species eats coralline aglae using its radula. The teeth
its radula are unique amoung marine invertebrates, as they are capped
goethite, and also with silica (opal). Goethite is an iron
that forms a hard crystalline cap around the teeth. A.
is also fairly unique amoung limpets as it does not appear to have any
defense response system to predators. Predators include the
koehleri and birds such as black oystercatchers and
and Fairbanks, 1966
and Carlton, 1975
and Brusca, 1978
and McConnaughey, 1986
et al., 1980.
and O'Clair, 1998
et al., 1985
General Notes and
Observations: Locations, abundances,
unusual behaviors, etc.:
This individual is crawling on a Nucella
lamellosa shell. It is covered with
coralline algae, which
is usually pink. The white color suggests that the coralline
is dead on this individual.
Photo by Dave Cowles, July 2005
The head, tentacles, and foot of this species are white.
Photo by Dave Cowles, July 2010
An underwater photo of Acmaea mitra by Kirt
Onthank, July 2007.
The limpet is encrusted with algae.
The two snails in the background are Calliostoma
Another individual, photographed in the intertidal. The
grazes on coralline algae, but some coralline algae also often overgrow
the limpet's shell. I do not know whether the algal
due to the fact that the limpet often rests within the algal colony or
whether the algae spores or gametes settle anew on the shell.
see anything else but coralline algae growing on the shell, so that may
imply that the overgrowth comes from resting within the algal
Note that many of the coralline algae encrusting the rock already seem
to have been grazed in this photo. Photo by Dave Cowles, July
Authors and Editors of Page:
Ryan Lunsford (2002)
Editors: Dave Cowles 8-2002, 2005
Hans Helmstetler 12-2002