The Limpet Life: Living in the most exposed sites: On wild and windy shores, it is remarkable that any life can gain a hold on the slippery, wet rocks, but acorn barnacles and limpets do. They clamp tightly to the rock face.
The Limpet Life: Living in the most exposed sites
The acorn barnacle is a crustacean surrounded by circular plates with a top that opens when the tide is in and closes when it goes out, preventing it from drying out. It can live in the most exposed sites because it glues itself to the bare rock surface using special cement from a gland at the base of its antenna; in effect, it lies upside down with its legs in the air, fixed to the rock by its forehead.
The limpet is a cone-shaped marine snail without any coiling of its shell. It has adhesive mucus, but also uses its powerfully muscular foot to fix it firmly to the rock by suction. Unlike the barnacle, the limpet can move around, although it always returns to exactly the same spot before the tide goes out.
The little oval patch it leaves on the rock – known as a ‘home scar’ – is kept clear of algae for maximum adhesion. The limpet feeds with a radula or ‘tongue’ lined with teeth that scrape algae from rocks. The teeth are made from the strongest material known in nature, even stronger than spider silk, and have a tensile strength up to thirteen times that of human teeth.
Once in place, the limpet is extremely difficult to budge. The crushing claws of large lobsters can break into them and oystercatchers will try to prise them off, but the champion limpet-eater is South Africa’s tadpoleshaped giant clingfish or rocksucker.