Description: A white, conical, acorn barnacle that can reach up to 20 mm in diameter. Form becomes more conical when crowded. The outer shell consists of 6 plates, with the rostral plate wider than the aperture. These plates are smooth in young animals, but become ribbed with age. The opercular aperture is diamond shaped or sometimes pentagonal, with a toothed rim. The visible suture in the aperture forms an arrow point and there are visible growth lines on the scuta. The tergo-scutal flap is edged in yellow.

Habitat: Usually found subtidally, but may occasionally be encountered on the very low shore. Found on a range of hard substrata, including artificial structures.

Distribution: Found around all coasts of Britain and Ireland.

Similar Species: Could be confused with other species of acorn barnacle, the suture in the shape of an arrow point and the visible growth lines help to distinguish this species.

Key Identification Features:

• White, conical barnacle up to 20 mm in diameter.
• Outer shell with 6 plates; smooth in juveniles but ribbed in older individuals.
• Diamond or pentagon-shaped aperture with a toothed rim.
• Growth lines visible on scuta.
• Suture in opercular aperture forms an arrow point.

Distribution Map from NBN: Balanus crenatus at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Balanus crenatus at iNaturalist World Species Observations database.

GBIF data for Balanus crenatus

WoRMS: Balanus crenatus at World Register of Marine Species. Accepted name: Balanus crenatus Bruguière, 1789. AphiaID: 106215.

Classification: Biota; Animalia; Arthropoda; Crustacea; Multicrustacea; Thecostraca; Cirripedia; Thoracica; Thoracicalcarea; Balanomorpha; Balanoidea; Balanidae; Balaninae; Balanus