Green Crab - Western Isles
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. 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.
This crab has powerful claws and rear legs pointed for gripping on to rocks. The adult Green Crab has a body width of around eight cm's and is usually a dark yellowy green colour
Younger Green Crabs - Yellow - Red - or Green
Younger crabs can be yellow, green or red with whitish markings. 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 is wide at the front with a series of bony serration's along the forward edge. The shell tapers inwards in a straight line towards the rear of the crab. They have three points between the eyes and five points on each side of the eyes.
Green Crabs can be found all around the English coast in rock pools under large stones and amongst bunches of seaweed. They are also well-adapted to living in diluted seawater. They are found under algae and rocks when the tide is out but live right down the shore into quite deep water. The green crab buries itself for protection in clean sand around individual rocks, lives happily in the holes and weed growth along harbour walls and pier and jetty supports.
The green crab is a hungry little beast. Their favourite foods are clams, mussels and scallops. They also eat worms, small gastropods, small crabs, algae, carrion and almost anything they can catch. The green crab can actually catch juvenile fish in their claws because they are very, very fast, unlike many rock crabs.
Green crabs are sometimes called the cockroach of the sea
Studies have shown that the green crab is quicker and more dexterous than most crabs, they can open bivalve shells in more ways than other crabs.
Chemical Detection System
The green crab or European shore crab, has evolved a very specialised chemical detection system. It uses this system to communicate via odour, with other crabs of the same species. These chemicals can increase or suppress appetite, attract the opposite sex and act as repellents.
The Green Crab's Enemies
Enemies: anything that can swallow it, depending on size and location. In the English Channel they are eaten by Bass and Gulls.
These crabs often get into fights with other crabs of their own type even.They lose claws in these fights, and many (up to 5%) adult crabs on the shore have missing claws or smaller claws re growing.
It is listed among the 100 "world's worst invasive types of invasive species
Moult in the Summer
The green crabs moult in the summer as their hard outer skin can only expand for a short time until it hardens.The crab’s main defence is a hard shell that covers the whole body. This hard shell is inflexible and so for the crab to grow it has to periodically shed it. This process of moulting is known as ecdysis. This is a time of danger for the crab, as its shell is now soft and requires time to harden.
Green Crabs or European or Shore Crabs as they are frequently called mate and then females produce around 185,000 eggs which attach to her legs until they hatch.
67 Species of Crabs around Britain
There are 67 species of true crab that live in the seas around the British Isles
|Inches and cm sizes are approximate|