Sleepy Sponge Crab

The Sleepy Sponge Crab (Dromia dormia) is a marine (saltwater) crustacean in the Dromiidae family of sponge crabs. It is also known as the Common Sponge Crab.

The Sleepy Sponge Crab is narrow at the mouth and widens at the base of its shell, called a carapace.  The carapace is an exo-skeleton (an outside skeleton). It has ten appendices, with two large nippers (claws) and eight smaller legs. The last two pairs of legs are shorter than the other legs. It walks sideways. It is beige-brown. It carries a sponge on its back, and sometimes other materials, such as wood. 

Sleepy Sponge Crab

It grows to about 17-20 centimetres (7-8 inches) across. 

It is widespread in the oceans of the Indo-Pacific region, from east Africa to Australia and Hawaii. It prefers shallow waters.

It cuts small pieces of living sponge into a home or shelter for itself. It trims the sponge into shape with its claws. The sponge grows with the crab, providing constant shelter.

The female Sleepy Sponge Crab carries many small eggs on her back, so she is ovigerous. The eggs hatch after about 25 days. They hatch into larvae that develop into adult crabs. 

Location of photograph: Natural History Museum, Paris, France

Photographer: Martina Nicolls


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