‘Limpet’ is a term that’s used to describe a variety of both freshwater and marine gastropods (kinds of slugs or snails). Many of these are only distantly related, with some using lungs and others relying on gills, but they all share a characteristic shell. These tough, conical-shaped shells are the key to the limpet’s success.
‘True limpets’ are often found in rock pools in the intertidal zone – an area above the water at low tide and below the water at high tide. When the tide is out they clamp down onto the surface of rocks to avoid being eaten and to stop their soft bodies from drying out. When the water returns, though, they’re highly active creatures. Using a simple nervous system they navigate the rocks in search of algae, which they scrape into their mouths using a ribbon-like tongue covered in rows of sharp, rasping teeth.
By grazing like this, limpets control the growth of algae in their habitat. Preventing the algae from taking over enables other marine and intertidal species to thrive, maintaining the health and balance of the ecosystem. In turn, the feeders become the food – despite their hard shells and strong muscles, limpets are never completely safe from the persistent hunting efforts of predators like crabs, fish, starfish and shore birds.
Humans have also historically collected limpets. They’re not the easiest animals to harvest, but the bodies of limpets can be eaten and their shells turned into jewellery and art. Their usefulness to humans has resulted in the introduction and spread of species outside of their natural range.