California Acorn Barnacle, Megabalanus californicus
California Acorn Barnacle, Megabalanus californicus. Cluster Size: 10 cm (4.0 inches) x 10 cm (4.0 inches) x 13 cm (5.1 inches).
Phylogeny: The California Acorn Barnacle, Megabalanus californicus (Pilsbry, 1916), is a member of the Balanidae Family of Acorn Barnacles. The subfamily Megabalaninae is one of ten subfamilies in the Balanidae Family, and Megabalaninae contains six genera. The Genus Megabalanus is comprised of thirty-six species. The genus name Megabalanus comes from the Greek words for “large acorn shell”. They are also known as the Red-striped Acorn Barnacle and the White-ribbed Red Barnacle and in Mexico as Percebe Californiano.
Morphology: The California Acorn Barnacle has steep sides with red and white striped plates that are separated by off-white plates. The mantle of living specimens is orange, red and blue. The top opening is wide that helps distinguish this barnacle from the similar Titan Acorn Barnacle. California Acorn Barnacles reach a maximum of 3.0 cm (1.2 inches) in diameter. This species can be confused with the Titan Acorn Barnacle, Megabalanus coccopoma, which is paler in color and has a smaller opening.
Habitat and Distribution: California Acorn Barnacles are found attached to hard surfaces including buoys, crustacean shells, mollusk shells, pilings and rocks, as individuals or in clusters. They are found in the intertidal zone, and to depths up to 12 m (40 feet). The California Acorn Barnacle is a subtropical to tropical Eastern Pacific species. They are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from north of Santa Rosalia, Baja California Sur, in the Sea of Cortez. Following an El Niño weather event, the California Acorn Barnacle can be found in more northern areas.
Diet: California Acorn Barnacles are suspension feeders. When immersed in water their cirri (thoracic limbs) emerge from the shell to gather detritus and plankton.
Predators: California Acorn Barnacles are preyed upon by crabs, gastropods, and starfish.
Reproduction: The California Acorn Barnacle is hermaphroditic and reproduces via broadcast spawning. The eggs are fertilized in the mantle cavity, forming planktonic nauplii larvae. After several larval stages the organism cements itself onto the substrate and undergoes metamorphosis.
Ecosystem Interactions: The commensal, parasitic, or symbiotic relationships of the California Acorn Barnacle has not been formally documented.
Human Interactions: California Acorn Barnacles can foul ship hulls, pilings, and other infrastructure. Otherwise, have very a limited impact on human activities. From a conservation perspective they have not been evaluated, but are common with a widespread distribution and should be considered to be of Least Concern.
Synonym: Balanus tintinnabulum californicus