Sponge Crab- Facts and Photographs

Cryptic Sponge crab Cryptodromiopsis spongiosa

The Sponge crab Lauridromia dehaani is not often seen due to their nocturnal habits. During the day they hide in crevices or holes and are usually only seen at night.  As their name implies they decorate themselves with a piece of poisonous sponge which they trim off a live sponge. The poisonous sponge acts as a deterrent to predators. This behaviour is known as Aposematism.  If the sponge is removed from the crab it will immediately attempt to obtain another piece.

APPEARANCE

The dome shaped carapace is covered in fine hairs which assist the sponge to grow onto the carapace. The rear legs are a adapted to hold the sponge onto the body.  The largest specimen we have seen has been approximately 15 cm in width. The edges of the chelepids are a pinkish white colour.

IN THE WILD

Sponge crabs are usually only seen at night, during the day they hide and are well camouflaged. When found they will usually scurry away or seek shelter even if it is behind or between sea urchins as the one in the images is doing. They have a very ungainly walk and have a grumpy look about them. They are usually only seen when they move, they do not enjoy the light from ones dive lights and head for cover once the light hits them. The size of the sponge varies greatly and some crabs appear to be better than others at trimming the sponge to fit them.

HABITAT

The sponge crabs are found on coral and rock reefs across the Indo-Pacific. They are usually seen in the rubble areas on reef tops.

Cryptic Sponge crab Cryptodromiopsis spongiosa

DIET

The sponge crab is carnivorous and although they are mainly scavengers, they will break open and eat any mollusc that they can open.

REPRODUCTION

Very little is known of the reproductive behaviour of the sponge crabs. After mating takes place and the eggs are fertilised they are kept on the underside of the female. After hatching the larvae go through a planktonic stage before maturing into young adults.

Cryptic Sponge crab Cryptodromiopsis spongiosa

SPONGE CRAB CLASSIFICATION

Kingdom:Animalia
Phylum: Arthropoda
Subphylum:Crustacea
Class: Malacostraca
Order: Decapoda
Infraorder:Brachyura
Family: Dromiidae
Genus: Lauridromia
Species:L. dehaani

LITERATURE CITED

EQUIPMENT USED

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