Pacific White Cap Limpet

Acmaea mitra is a sea snail, specifically a limpet. Its body has a soft, muscular foot, which secretes a hard, cone-shaped shell. This is an entirely white limpet, but it is often encrusted by a coralline red alga. The shell is thick, taller than other local limpets, and the apex is only slightly anterior to the center. The surface may be sculptured with fine concentric growth lines and radial striations. Length to 3.5 cm, height to 3 cm. This limpet is easily identified by its color and height. Note: Formerly nearly all our intertidal limpets were classified in family Acmaeidae. Now most of the others have been moved to family Lottiidae, and this is the only species left in family Acmaeidae.

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.

A. mitra can be found whereever red coralline algae is present.

Geographical Range: Aleutian Islands, Alaska to Baja California.

Depth Range: Low intertidal and mostly shallow subtidal

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. 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 Orthasterias koehleri and birds such as black oystercatchers and white-winged scoters.