The red thatched barnacle is structurally composed of three calcareous parts: one which helps the barnacle adhere to the surface and known as the basis, a four plate wall referred to as the compartment, and the two pairs of plates/valves on the surface that open and close (1). Each overlapping region of the wall is not distinguishable externally thus further classification of this barnacle is by the red color of the calcareous plates of this non-moving (sessile) barnacle (1). It is often referred to as the volcano barnacle and they occupy upper rocky intertidal zones with this species ranging from Baja California up to shores near San Francisco (1). Certain marine snails heavily prey on the Red Thatched Barnacle which dictates their distribution and abundance (2).
(1)Newman, W.A., Abbott, D.P., 1980. Cirripedia: the barnacles. In: Morris, R.H., Abbott, D.P., Haderlie, E.C. (Eds.), Intertidal Invertebrates of California. Stanford University Press, Stanford, California, pp. 504–535
(2)Sanford, E., & Swezey, D. S. (2008). Response of predatory snails to a novel prey following the geographic range expansion of an intertidal barnacle. Journal of Experimental Marine Biology and Ecology, 354, 220-230.
(Photograph) Sherry Ballard © California Academy of Sciences