Believe it or not beneath this sponge is a crab! If you look closely you should be able to make out the lighter coloured carapace. Sponge crabs are able to carry a piece of living sponge on their back by holding it in position with their last two pairs of legs. These legs are smaller, directed more or less upwards and bear small pincers. Those crabs deprived of their personal sponge caps will go to great lengths to retrieve them. If all else fails they will cut and shape new caps.
It's not a simple task for a crab to re-dress! In putting on the sponge cap the crab may need to grasp the cap, roll over on its back, upend itself backwards and then right itself.
Why go to so much trouble? As you can see from the picture a sponge crab that is "well capped" is perfectly camouflaged. This "disguise" enables the crab to be less of a target to any predators looking for a crustacean meal.
Species of Stimdromia are unusual among crabs in that young crabs hatch from the eggs carried by the female and stay with the mother for several weeks. There is no planktonic larval stage.
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Feedback and queries should be sent to the Discovery Centre at Museum Victoria.
Please note, the Discovery Centre can help you only with questions about crustaceans from southeastern Australia. It can not advise on the care of pet hermit crabs or on crustaceans from other regions.