Poli's Stellate Barnacle

Overview

Poli's Stellate Barnacle is a common, sessile crustacean frequently found on rocky shores throughout the northeastern Atlantic and Mediterranean. These barnacles are highly resilient, capable of surviving long periods of exposure to air and drying conditions during low tide.

Appearance

This species typically resembles a small, flattened volcano, with a shell composed of six solid, white to yellowish calcareous plates. While generally conical, individuals may appear more tubular when growing in dense, crowded colonies. A key identifying feature is the vivid blue tissue with black and orange markings, which may be visible when the opercular aperture is slightly open. Juveniles possess a kite-shaped opening, which develops into a broader, oval shape in adults.

Distribution & habitat

They are primarily found on hard substrates, such as bedrock and boulders, in the upper and mid-intertidal zones. They thrive in areas exposed to wave action and are often found in large, dense clusters. Their range extends from the British Isles and Ireland south to the Azores, Madeira, the Cape Verde Islands, and along the coasts of northwestern Africa and the Mediterranean.

Biology & behavior

As adults, these barnacles are permanently attached to their substrate. They are hermaphroditic and can self-fertilize if isolated, though they typically reproduce by exchanging gametes with nearby individuals using a long, flexible penis. They are suspension feeders, using rhythmically beating, feathery appendages to capture plankton and detritus from the water column when submerged.