The Seaweed Decorator Crab (Notomithrax ursus) is a very unusual looking crab species that belongs to the Spider Crab family Majidae. This species is rather common along the south-east coast of Australia however it is seldom seen as it very well camouflaged with its algae covered body. It can be found in the coastal waters of new South Wales, Victoria and Tasmania and generally is found on intertidal reefs in shallow water. Spider crabs are characterised by triangular or occasionally rounded carapaces that are covered in spines, hairs and knobs. The crabs use their claws to camouflage and decorate themselves by attaching hydroids, algae or sponges to their hairs. Once attached these attached ‘plants’ grows on the body of the crab.
The Seaweed Decorator Crab (Notomithrax ursus) has reddish-orange claws that have lightly covered tips have two granulose ridges along the segment before the hand. The Seaweed Decrator Crab has a maximum carapace width of approximately 4cm.