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 eroded by a burrowing species.|
|Photo by: Ryan Lunsford 2002|
How to Distinguish from Similar Species: Acmaea
mitra is the only all white limpet, and is much taller and conical
like a miter or short dunce's cap than are other limpets.
Geographical Range: Aleutian Islands, Alaska to Baja California.
Depth Range: Low intertidal and mostly shallow subtidal
Habitat: A. mitra can be found whereever red coralline algae is present.
Biology/Natural History: Acmaea
mitra is known by its tall shell, which can reach a height of 30 mm
and a length of 35 mm. The scientific name means "pointed cap".
This species eats coralline aglae using its radula. The teeth of
its radula are unique amoung marine invertebrates, as they are capped with
goethite, and also with silica (opal). Goethite is an iron compound
that forms a hard crystalline cap around the teeth. A. mitra
is also fairly unique amoung limpets as it does not appear to have any
defense response system to predators. Predators include the seastar
koehleri and birds such as black oystercatchers and white-winged scoters.
|Main Page||Alphabetic Index||Systematic Index||Glossary|
Brusca and Brusca, 1978
McConnaughey and McConnaughey, 1986
Morris et al., 1980.
O'Clair and O'Clair, 1998
Ricketts et al., 1985
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 algae 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 ligatum.
Another individual, photographed in the intertidal. The limpet grazes on coralline algae, but some coralline algae also often overgrow the limpet's shell. I do not know whether the algal overgrowth comes 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. I rarely see anything else but coralline algae growing on the shell, so that may imply that the overgrowth comes from resting within the algal colony. Note that many of the coralline algae encrusting the rock already seem to have been grazed in this photo. Photo by Dave Cowles, July 2010.