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Underwater photography: images of crabs taken while scuba diving
Land crabs | Arrow crabs | Hermit crabs | porcelain crabs | Decorator crabs | Swimming crabs
Class: Malacostraca Order: Decapoda Subphylum: Crustacea Phylum: Arthropoda

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.

image gallery

click any image to enlarge
Int. = intermediate stage
Juv. = juvenile

The threat to crabs species vary widely from 'data deficient' to threatened.

Land crab encounters...

Gecarcoidea natalis
Red crab
Birgus latro
Robber crab

The most famous animals on Australia's Christmas Island are the ten-legged ones. There are crabs everywhere – in the forest and on the beaches just as you would expect. But at certain times of year they are also everywhere else... climbing fences, over the car and into the house. Once the red crabs start their annual migration the whole island ripples with red.

a stunning natural event and one that eclipses the fact that there are many other land crabs on the island, around 20 terrestrial and intertidal ones. Of those,13 are true land crabs that only enter the ocean to spawn. It would be hard to miss these or the robber crabs, Birgus latro, which are absolutely enormous, growing up to 40cm. They are bold creatures that live up to their name.

Christmas Island robber crab
SPECIES NAMES | Many fish can be hard to identify as they are so similar. Common names vary and even scientists disagree on what is what. If you can name anything we can't, please get in touch.

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