Volcano Barnacle

Overview

The Volcano Barnacle (Perforatus perforatus) is a large, distinctive crustacean easily recognized by its tapered, volcano-like shell. It is commonly found in groups attached to hard surfaces, such as rocks, sea walls, and ship hulls, throughout the warm temperate waters of the eastern Atlantic Ocean and the Mediterranean Sea.

Appearance

This species features a shell composed of six fused, vertically ridged plates that are typically pale purplish-brown in color. The shell often reaches a diameter and height of up to 3–5 cm, with the plates sometimes separating at the apex to create a jagged, crater-like opening. When the barnacle is active, the operculum—a set of movable plates at the top—opens to reveal brightly colored tissue in shades of pink, purple, and blue. When closed for protection or during low tide, the aperture is sealed by a purplish-brown flap marked with blue and white spots.

Distribution & habitat

Perforatus perforatus is distributed along the eastern Atlantic coast, ranging from western Africa to the English Channel, as well as throughout the Mediterranean. It occupies the mid-shore to sublittoral zones, thriving on both natural rocky substrates and artificial structures. While it prefers warmer waters, its range has shown signs of expansion in recent decades.

Feeding

Like other barnacles, this species is a filter feeder. It extends specialized, feather-like appendages called cirri from its aperture to comb the water column, capturing plankton and organic detritus for nutrition.

Reproduction

Reproduction typically occurs between May and September. Adults release larvae into the water column, where they drift and molt before eventually settling onto a suitable hard surface to develop into their adult form.