With over 6,700 species in 93 families in the animal kingdom, these crustaceans have been roaming our waters for millions and millions of years. Usually covered in a thick exoskeleton and armed with a pair of claws, they could be found all over the world, most in the oceans while others in bodies of fresh waters. Their size varies from the extremely small pea crab, which measures .75 centimetres, to the extremely large, record holding, Japanese spider crab, which is all of 4 metres.
They are known as decapods because of the fact that they have ten appendages, from the Greek words, deka which means ten and poda which means leg. They have identical halves on each side except when one of their chelae or pincers is larger than the other. These claws serve many functions, for instance capturing food, digging holes, defending from predators, and communication with other crabs to mark territory and to attract the opposite sex.
Their bodies are completely covered with an exoskeleton which also serves as a suit of armour. Every so often, the decapod would need to shed it in order for it to grow bigger. The process of replenishing a new exoskeleton only takes a few hours. Sexuality can be determined just by looking at their abdomens. The male species would have a narrower region than that of the female.
Crabs, generally, walk sideways because of the articulation of the legs. Some, however, are capable of walking forwards and backwards. Being omnivores, they feed on anything from algae to molluscs, fungi, bacteria, worms and even other crustaceans.
Every year we consume an estimated 1.5 million tonnes of crabs which make up about 20 percent of all the crustaceans which are consumed. Of this amount, 300,000 tons are made up of the Japanese Blue Crab or the Horse Crab which is the most consumed around the world and is indigenous to the coasts of China.
Crabbers are the people who specialise in capturing decapods in various bodies of water. They use a cage-like device with a one-way door which allows the creatures to go in but not out. People who do it for recreational purposes, on the other hand, use a piece of bait which is tied to a string and tossed in the water. The fisherman simply pulls the line in when they start taking the bait. Of course, there are other methods for capturing these animals.
One thing you have to be aware of before you go out and fish for crabs is that there are laws regulating this activity. Check for your local fish and game department for more details