A small sessile barnacle, 5-10 mm in diameter, Darwin's barnacle, Austrominius modestus is characterised by having four shell plates which form a low, conical body shape with a diamond shaped opening. This barnacle is distributed around most coasts of England and Wales, a few areas of Scotland and some Scottish islands including the Outer Hebrides. It is native to Australasia and was first recorded in Britain in the 1940s.
It is most common in the mid-shore to shallow subtidal areas of estuarine and sheltered marine habitats, and tolerates a wide range of temperature and salinities. It attaches to a variety of substrates including rocks, stones, hard-shelled animals and artificial structures including ships.
Darwin's barnacle competes with native species for space and appears to have entirely displaced native barnacle species in some places. Economically its main impact is the costs arising from the fouling of vessels, equipment and interference with mariculture activities.
Information and Identification Sheets: Darwin's Barnacle