is the most
common species of barnacle in the Gulf of California. This small
(<7 mm basal diameter) virtually defines one of the key intertidal
zones of this region.
In the northern Gulf of California, there are two morphs of the barnacle. One morph is the typical volcano-shaped form (shown here) that is characteristic of acorn barnacles. The other morph appears bent over, with the rim of its aperture oriented in a plane that is perpendicular to the base. This bent form is induced by and more resistant to attack by the predatory snail, Acanthina angelica, which is restricted in its distribution to the northern Gulf of California.
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