Sponge Decorator Crab Hyastenus elatus

Family: Majidae

"The sponge decorator crab is a master of camouflage. They are very common in sponge gardens but often go unnoticed by divers."

The Sponge Decorator Crab (Hyastenus elatus) belongs to the Spider Crab family Majidae. Crabs in the Majidae family are unique in that they have triangular body that tapers towards the front however some species may have a rounded carapace. The carapace of the Majids is generally covered with spines or knobs and has hooked hairs. These hairs are very important as the crab attaches algae, sponges and hydroids to the carapace via the hooked hairs.

The Sponge Decorator Crab can be identified by its pear shaped carapace with two long rostral projections that are nearly as long as the body and two shorter projections from the side. The Sponge Decorator Crab attaches pieces of sponge to its body, which grow around the carapace and it's legs. As the crab grows the attached sponges and anemones grow with it

The Sponge Decorator Crab is distributed around tropical Australia from Fremantle on the west coast north around to Shellharbour on the east coast. It is also found in other parts of the west Pacific including Indonesia and Papua New Guinea. It lives in sponge gardens, especially in estuaries and coastal bays. During the day divers often don't notice them as they hide at the base of sponges but they become more active at night and can be found sitting on top of the sponges. They can be found from 1 metre down to a depth of 54 metres. The maximum size the carapace grows to is approximately 8cm.

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