Crabs - Western Isles - Hebrides Crustacea
The Hebrides or Western isles is a great place to see crustaceans.
There are many different types of crabs to be seen throughout The Hebrides. The great beaches here mean that you can easily spot many different crabs.
Crabs belong to a group of animals known as the Crustacea. The soft body is protected by a hard outside shell known. Unfortunately, this hard shell does not grow.
Soft Shell Grows
A soft shell grows inside the crab. Eventually, the crab grows too big and it has to shed its old hard shell. This shedding of this shell or 'moulting' is a very dangerous time for the crab. The new shell is larger than the old one, but it is soft and takes time to harden. While it is soft, the crab tries to stay hidden so that it is not attacked by hungry fish and other animals.
Grows Back Lost Claws
During the moult, the crab can grow back a lost claw, but it will be smaller than the one that was broken off. The old discarded shell looks like a dead crab, but if you look closely you will find there are holes
Crabs carry their eggs on Their Undersides
Female crabs often carry a clump of eggs on the underside of their body. They are cared for for several months before the eggs hatch into tiny swimming crab larvae which are released into the sea. The larvae join the plankton (lots of small plants and animals that live and grow in the top waters of the sea).
Larvae Turn into Crabs
After a few months, the larvae that have survived fall to sea bottom and turn into tiny adult crabs. In the summer hundreds can be found on rocky shores.
Crabs for Food
Crabs give us great nutritional benefits.
Prey for Many Fish and Mammals
Crabs are a popular prey for many birds fish, and mammals.
The Green Crab
The green crab (Carcinus maenas) is a small shore crab. The adult crabs are probably about 3inches across. It is the European crab and is known by the common name of green crab. This crab has ten walking legs with two large pincers on the first pair and its right-handed pincer is bigger than the left. It also has two pairs of antennae of which one pair is quite long
The shell however can vary from dark, mottled green to orange or red, with yellow patches. You can see many of these shore crabs along the Western Isles Beaches.
Click pictures below for larger photographs
The masked crab or sand crab as it is often called - seen here in The Western Isles - and on The Isle of Lewis and The Isle of Harris has an elongated reddish brown to yellow in colour carapace. It sometimes has features patterns that look like a face and of course easily identified by the long pointed tube.
The bristly antennae are much longer than the carapace. The first pair of walking limbs or 'pereopods' have pincer and are about twice the length of the carapace in males, (the same length as the carapace in females)
A Hermit Crab
There are more than 100 different species of hermit crab found in marine habitats around the world. Although hermit crabs are seen in deeper waters, hermit crabs are more usually seen in coastal waters where there is more food and places to hide.
Hermit crabs use whatever shells are available that are the right size in order to protect themselves and as they grow in size, they search for another shell to use as their home. One empty shell on a beach can trigger a rush and as one crab gets a larger shell for a "home" another smaller crab gets a new home.