Volcano Barnacle, Tetraclita stalactifera

Volcano Barnacle, Tetraclita stalactifera. Barnacle collected from rocks from within a tidal pool in the greater Los Cabos area, Baja California Sur, January 2018. Diameter: 1.8 cm (0.7 inches).

Volcano Barnacles, Tetraclita stalactifera. Photograph taken within an exposed tidal pool in the greater Los Cabos area, Baja California Sur, January 2018.

Phylogeny:  The Volcano Barnacle, Tetraclita stalactifer (Lamarck, 1818), is a member of the Tetraclitidae of Volcano Barnacles. The genus Tetraclita is one of nine genera within this family, and it is comprised of  nineteen species. The Volcano Barnacle is also known as Ribbed Barnacle. In Mexico it is called percebe volcán.  There is some variation in this species throughout its wide distribution. This has given rise to several proposed sub-species. Some of these subspecies have been reclassified as new species, and some have been dismissed. Currently, there is only one recognized subspecies of the Volcano Barnacle, Tetraclita stalactifera confinis.

Morphology: The Volcano Barnacle is comprised of four fused plates, in the shape of a volcano. Numerous ribs run from top to bottom on these barnacles. They may be blue-gray, light gray, greenish, or whitish in color. They are large barnacles, reaching 5.0 cm (2.0 inches) in diameter.

Habitat and Distribution: The Volcano Barnacle is found attached to hard surfaces such as debris, pilings, rocks, and wreckage. They reside primarily in the higher intertidal zone to depths up to 40 m (130 feet). The Volcano Barnacle is a resident of all Mexican waters, both the Pacific Ocean and the Atlantic Ocean, with the exception that they are absent from the west coast of the Baja Peninsula.

Diet:  When submerged Volcano Barnacles extend their feathery feet through the top of the volcano. These feet function like gills to extract oxygen from the water, and they also filter plankton and detritus from the water for food.

Predators:  Volcano Barnacles are preyed upon by numerous sea stars and murex gastropods such as the Brevidentata Murex, Acanthina brevidentata.

Reproduction:  Volcano Barnacles are hermaphrodites, with each individual having both male and female reproductive organs. They reproduce sexually through broadcast spawning. Fertilization occurs in the mantle cavity. Once the eggs hatch they are expelled into the sea and undergo several larval stages while drifting as plankton. After some time they settle to the bottom and metamorphose into their adult form.

Ecosystem Interactions: Unlike many other barnacles the Volcano Barnacles do not attach themselves to sea turtles, crustaceans, or marine mammals.  There are no documented reports of the Volcano Barnacle engaging in any types of parasitic, commensal, or symbiotic relationships.

Human Interactions:  Volcano Barnacles have little direct impact on human activities. They do have the ability to foul ship hulls and other submerged infrastructure, but do not seem to be a significant problem. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern