Common Shore Crab a familiar seaside animal

By Jim Hurley - Nature Trail

Published 07/07/2015 | 00:00

The Common Shore Crab is often found at this time of year.
The Common Shore Crab is often found at this time of year.

The Common Shore Crab is a very familiar seaside animal and is often found at this time of year be it while dabbling in rock pools on a sunny day or fishing for crabs off a pier.

While it comes in a great variety of mottled colours its predominant colour is dark green. It is a meat-eater so it will readily take bait on a length of line without the need for any hook. Its powerful grip means that a hungry individual will cling to the bait and allow itself to be hauled out of the water. In the wild its diet comprises snails, worms, other marine creepy-crawlies and dead things.

Handling it is another matter. Crabs, lobsters, crayfish, prawns and shrimps belong to a large order of creature called the decapods, that is, they all have ten legs. Four pairs of legs are used for walking and the crab is well known for its ability to scuttle sideways as well as going forward and being able to reverse.

If threatened the crab lies back, digs its hind legs into the ground for anchorage and support and rears up with its front pair of legs ready to attack. The front pair of legs have evolved into pincers and while it seldom draws blood a pinch from them can be memorably painful. Consequently, lots of people are understandably fearful of the crustacean's waving weapons.

The Common Shore Crab has two forward-pointing eyes. Between these eyes it has three bluntly-rounded teeth and to the outside of each eye its shell projects forward in five pointed, spiny teeth.

Crabs are different from us in that they have their skeleton on the outside. We can feel the bones in our forearm on the inside with flesh on the outside. Crabs have their hard parts on the outside of their bodies and legs and are entirely soft within.

One of the big drawbacks with the crab's arrangement is its shell doesn't grow with it. So, as the crab grows its shell becomes too tight, like shoes on a child's feet, and it has to shed it and grow a new one.

When it sheds its outer skeleton it goes around naked for a while until it grows a new shell. At that stage it is known as a 'peeler' and unless it hides away it can become a particularly tasty morsel for a hungry fish, other predator or angler searching for bait.

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