Arrow crabs, hermit, Chinese mitten, porcelain, decorator, cryptic tear drop! Think of as many weird names as you can and you still won't match the number of different crabs in the world. There are around 4,500 species all told and most live in the sea.
However, there are a few stragglers that prefer life in fresh water while some like it on dry land. Yet even land crabs, which are abundant in tropical countries, use the sea on occasion – in their early or reproductive stages.
Not all crabs are true crabs... true crabs are decapod crustaceans of the infraorder Brachyura. They have a very short projecting "tail" or a reduced abdomen hidden under the thorax. Hermit crabs, king, porcelain, horseshoe crabs and crab lice are not true crabs.
Crabs play much the same role in the sea as insects on land. They are scavengers, reef cleaners and gardeners and a great part of the food chain supplying sustenance for creatures as large as whales.
One sixth of all freshwater crab species are threatened with extinction. All marine crabs suffer through erosion and loss of habitat.
