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Limpets – do they return to exactly the same place each time the tide goes out? I’ve noticed the ones stuck to irregular surfaces have the fringe of their shell shaped to fit the surface (like a jigsaw puzzle), so they must return to the same spot and shuffle around to exactly the same orientation too. Who’d have thought that? Incredible! Or am I wrong? Steve, Edinburgh

Steve is absolutely right. Limpets are true homebodies, returning to exactly the same spot on the rocky shore at each tide. As they settle into position, their shells grind against the rock and, over time, they form an indentation called a scar. The limpet’s shell fits snugly against this scar and forms a tight seal that prevents the limpets drying out when the tide goes out. Like many animals that live on the shore, they have to tolerate the cycle of being exposed and inundated by seawater twice a day. They also have to endure strong wave action, drying out (limpets can survive up to 65 per cent water loss) and alternating extremes of temperature – from baking in the summer sun (well, sometimes!) to freezing cold seawater. Limpets are tough!

They’re also renowned for their ability to cling onto the rock using their powerful, muscular foot for suction and ‘glue’ for adhesion. This not only helps them to retain water but also deters predators such as birds. That’s not their only defence, though; limpets use moves that a wrestler would be proud of! They can ‘mushroom’, lifting their shell upwards then bringing it down suddenly, stomping on any starfish or other marine predator that comes too close.

At only six centimetres across and three centimetres high it’s easy to underestimate these apparently simple creatures, but limpets are architects of their environment. Their grazing keeps algal growth in check, removing young seaweeds. They have a special rasping organ called a radula with sharp ‘teeth’ set in 160 rows, each containing 12 teeth. Their tips are hardened with iron and silica. Limpets move across the rocks, grazing on a thin film of algae or small larvae. You may be able to see the scraping marks, pale zigzag lines, left behind on the rocks. As they slowly wander across the rocks they leave a trail of mucus in their wake. Before the waters recede, each limpet retraces its route, following chemical cues in the mucus, back to its home scar. The mucus also increases the amount of algae that settles and grows, so in effect the limpets are ‘farming’ their food. There’s much more to the humble limpet than meets the eye.