![]() ![]() Before the tide goes out, each limpet returns to its own ‘home’.Īpart from the dog whelks and limpets, several other molluscs live in the intertidal zone. When the tide covers their rock, or in wet, cool weather, the limpets leave their base and wander about, grazing on young seaweeds which have started growing on the rock surface. A strong foot muscle gets a firm grip on the rock, making it difficult for birds to prise off the limpet! This tight fit allows the limpet to trap a spoonful of water inside to stop it drying up. On soft rock, the limpet grinds it with its shell to make an exact fit on hard rock, the shell is ground down to fit the rock’s shape. Each limpet has its own ‘home’ – an exact spot on the rock where it stays when the tide is out. The limpets are perhaps the most well-adapted of all the marine snails for a life on the exposed rock surfaces. The dog whelk itself may be attacked by crabs and herring gulls. If you find an empty limpet shell with a small, neat hole in it, this is the work of the dog whelk. The whelk also attacks other molluscs, particularly the limpet, by either producing a shell-dissolving acid which makes a hole in the shell or by boring a hole through the shell using its rough, belt-like tongue. It is the favourite prey of the dog whelk which wanders up from the middle shore to attack the barnacles. The barnacle thrives in exposed conditions high up the shore, but even here it is not safe from predators. When covered by the sea, the operculum opens and six pairs of feathery legs (the equivalent of other crustaceans’ legs) appear and filter out particles of food. When exposed to the air, the barnacle closes its opening with a hinged trapdoor-like operculum – this is made of two limy plates which join up with other plates to protect the body. These crustaceans start life as tiny larvae floating in the sea with the plankton, and most come to rest in the intertidal area of a rocky shore, cementing themselves firmly to the rock. The upper shore is usually dominated by barnacles, particularly the acorn barnacle. They are often eaten by their relative the common star fish. In shallow water they are more active at night to avoid predators and will hide in dark crevices in the day. They feed on plankton and detritus - decaying matter which they put in to their mouths, a hole which they also use to extrete from. This isn't a problem for them as it can grow another arm within months and if the broken arm has a piece of the central disc attached, it can turn into a whole new brittle star! It can also cast off an arm if it is injured. ![]() Their name refers to how easily their arms will fall off when touched. ![]() They usually have 5 arms covered with spines. ![]() Some can swim but most crawl along the sea bed using their flexible arms. Here are some of the more common animals you can expect to find on the rocky shore.īrittle stars are not fish at all but are echinoderms, distantly related to sea stars. When the tide is out, birds such as gulls and oystercatchers search the shore, probably amongst the seaweeds for animals. Some species live almost as land animals around the high water-mark of spring tides, and others are only briefly exposed to the open air at the low water-mark of spring tides.Īll the animals are adapted to feed and breed during the few hours when they are covered by the tide. Like the plants, the animals are greatly influenced by the tide. The animals show a similar zonation, but because they can move around it is not so obvious. As we have seen, the seaweeds of a rocky shore grow in different areas – zones – depending on their ability out of the water. ![]()
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