Hi! I'm a prawn or maybe a shrimp, what do you think?

Prawns and shrimps are very similar and often we use the wrong name for them.

Shrimps have only one pair or legs with claws whereas prawns have two pairs with claws. But in total we both have ten legs and so do crabs and lobsters. We are all called decapods which, surprise, surprise, means having ten legs!

Prawns and shrimps eat all sorts of different foods including plankton and waste found in the mud. We have quite a thin skeleton and it is on the outside of our bodies. It is called an exoskeleton . The skeleton on a lobster is much thicker and stronger than ours and crabs have a skeleton which is so thick that it is called a shell. Lobsters' claws are much bigger and stronger too and are called pincers. They can give you a very nasty pinch and might even take off a finger! They use these pincers to chop up other dead sea animals such as starfish and fish. So do crabs and they will often "bite" too.

There are three main types of crab found around the Hebrides illustrated in the drawing on the right. There is the Green Shore Crab (pictured top right) which is green! And the large Edible Crab (pictured top left) which is edible! That means it is really good to eat. It has an edge to its shell which looks like the edge of an old-fashioned pie crust. Then there is the Velvet Swimming Crab (pictured on bottom) which has a soft velvety covering to its shell and its legs are flattened to help it to swim. If you manage to catch a crab to feel its shell please make sure you put it carefully back where you found it. And watch your fingers!

Crabs, lobsters, shrimps and prawns are all Crustaceans and so are barnacles (see the drawing below). Inside the shells are little tiny shrimps glued to the rock. When the tide comes in and the barnacle gets covered with water, then the shell opens and the little shrimp sticks its legs out and catches plankton from the water. Barnacles can be glued on whales.They are just along for the ride. They don't harm the whales or feed on the whales.

Jellyfish don't have any shell at all. Their body is just a blob of jelly with tentacles underneath which they use to catch their food. These tentacles can sting so that they can stun small fish and other little animals. There are two types found around the Hebrides . The Lion's Mane jellyfish has a large golden brown body and very long tentacles which you can hardly see. But watch out! They can give you a very nasty sting especially if you get them tangled round your leg! The Moon Jellyfish is smaller and almost clear but sometimes has purple rings too. It has only very short tentacles around the edge of the "bell" as the body is known. These don't sting us and it is quite safe to swim amongst them if you don't mind the slimy, squishy feel of swimming amongst a lot of jellyfish!

There is another large group of animals found in the sea whose shells we find washed up on the shore. These are the shellfish. They aren't fish living in shells but are more like snails and should be called marine snails. They include limpets, mussels, winkles and whelks.

Also scallops, oysters and clams. In fact there are so many different types that it is impossible to cover them all here. If you are interested in these shells and the animals which make them then you should borrow a book on shells from your library. You might be able to find a tiny periwinkle which only grows about 5 mm long or you might find a Red Whelk which can be up to 20 cm long

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Whelks are fascinating since they have a very easily seen proboscis or tube which sticks out of their shell and lets them prise open other shells such as mussel shells and to eat the snail inside.

Hermit crabs carry their shell homes on their backs and insert themselves inside for protection. They have 2 large claws called chelipeds, 2 sets of legs that they extend outside their shell for walking and 2 pairs of legs that they use to move their body around inside the shell.

They use other animal's old shell (especially whelk shell). hermit crabs hardly ever leave their shell, but when their home gets too small they go searching for a new one.

Most hermit crab species live on the ocean floor, but many live on land. Female terrestrial (land bases) hermit crabs must return to the sea to breed.

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