Tetraclitidae Family of Volcano Barnacles

One Volcano Barnacle of the Tetraclitidae Family can be found in this website:

Volcano Barnacle, Tetraclita stalactifera. A representative of the Tetraclitidae Family of Volcano Barnacles.

Phylogeny: Volcano Barnacles of the Tetraclitidae Family are in the phylum Arthropoda, meaning that they have jointed legs. They are in the subphylum Crustacea, along with crabs and lobsters. They are in the class Theocostraca, the superclass Multicrustacea, the class Thecostraca, the subclass Cirripedia, the infraclass Thoracica, the superorder Thoracicalcarea,  the order Balanomorpha, and the superfamily Coronuloidea. The Tetraclitidae Family is one of five families in this superfamily. The Tetraclitidae Family contains nine genera, one subgenus, and fifty-four species. The name Tetraclitidae comes from Greek and Latin and means “four-plated”. This refers to the four fused plates that make up the “shell”. Species in this family are also known as Thatched Barnacles.

Morphology: Unlike some other barnacles, Volcano Barnacles do not have a stalk and instead attach to the substrate with their shell. The cone-shaped shell is composed of chitin, the same material found in crab and lobster shells. The shell consists of four plates (parietes) fused together, in the shape of a volcano. They actually glue their head to a hard surface and then secrete a chitin shell around themselves. In some species the parietes have vertical parietal tubes. In the center of the volcano is an opercular valve structure comprised of two tergum and two scutum plates. When the animal is submerged, it opens the operculum and extends its cirri (feathery feet). These animals lack gills and absorb oxygen through their cirri. The parietes may be white, pink, gray, or green. Volcano Barnacles can reach a maximum of 5.0 cm (2.0 inches) in diameter.

Habitat and Distribution: Volcano Barnacles are found attached to rocks, crabs, pier pilings, sea turtles, and other hard surfaces. They live from the intertidal zone to depths in excess of 2,000 m (6,560 feet). Volcano Barnacles are found worldwide in tropical to temperate seas. At least three species from this family are found in Mexican waters.

Reproduction: Volcano Barnacles may be simultaneous or sequential hermaphrodites.  They reproduce sexually with internal fertilization. Because they are sessile organisms, they can only reproduce with individuals that are anchored nearby. The fertilized eggs are brooded within the shell. The eggs hatch into planktonic, shrimp-like larvae. This phase is brief and they eventually attach themselves to a hard substrate.

Ecosystem Roles: Volcano Barnacles are suspension feeders. When the animal is submerged it extends its feathery feet (cirri) through the top of the volcano. These cirri filter plankton and detritus from the water for food. They are preyed upon by crabs, fish, gastropods, and sea stars. Volcano Barnacles begin life as planktonic, shrimp-like larvae. When they are ready to settle out, the larvae become highly selective in location as once they attach to a hard surface, these animals are unable to change locations. There may be up to 70,000 larvae per square meter in a quality location, which then have to compete with algae, limpets, and mussels.