About Megabalanus californicus (Pilsbry, 1916)
Megabalanus californicus is a large acorn barnacle that can reach a maximum diameter of 30 mm (1.2 in). Its steep-sided shell is made up of six plates, marked with fine vertical stripes in reddish-purple and white. Where the plates fuse together, they have relatively wide, reddish radii. The mantle, visible through the barnacle's wide aperture, has a margin colored red, orange, yellow, and blue. This species can be mistaken for Megabalanus coccopoma, but M. coccopoma is paler, has a smaller aperture, and has narrower radii between its plates. Megabalanus californicus lives in the Eastern Pacific Ocean, found in the subtidal and intertidal zones of rocky shores. Its range stretches from northern California south to the Gulf of California. It typically grows in groups, and is most commonly found growing on pilings and buoys. In the year after an El Niño event, this species is often observed to have expanded its distribution further north.
