if you learn only 3 things about them ... They use living sponges or ascidians as a disguise. Specialised legs grip the disguise. They tend to move slowly.

Where seen? This intriguing crab is sometimes seen on our Northern shores, in coral rubble and seagrasses areas.

Features: Body width 0.5-5cm, although sometimes larger ones are encountered. The nearly spherical body is smooth and covered with fine hairs. The sponge crab uses its pincers to snip out a cap out of a living sponge to fit over its body. To grip this cap as it walks around, the crab's last pair of legs are slender, bent over its back and tipped with sharp little claws. The crab may also use an ascidian.

The sponge continues to live and grow and the crab constantly trims it to the right size. The sponge camouflages the crab so well that it is almost impossible to spot unless it moves. The sponge doesn't only disguise the crab. Sponges usually taste bad so this may discourage predators from taking a bite out of the crab even if it is discovered. Like other crabs that rely on a disguise, it tends to move slowly.

What does it eat? The sponge crab is a scavenger eating dead plants and animals that it comes across.

Sponge crab babies: Females have distinctive longitudinal grooves on the underside. The eggs of some species hatch into young crabs instead of free-swimming larvae. These young shelter for some time under their mother's abdomen.

• Sponge Crab (Cryptodromia sp.) Tan, Leo W. H. & Ng, Peter K. L., 1988, A Guide to Seashore Life. The Singapore Science Centre, Singapore. 160 pp.
• Sponge crabs on the Marine Crustaceans of Southern Australia page on the Victoria Museum website: brief info and photos of a crab with and without its sponge
  
• Dresser crabs are abundant but hard to spot on SusanScott.net: an interesting article about Sponge crabs in Hawaii. One was found using the toxic Crown-of-Thorns seastar as its disguise and is apparently one of the few creatures than CAN actually happily eat its hat.
  
• Crab with a ton of sponge on Philip Slosberg's page: a photo of a crab with a huge sponge on its back.

• Ng, Peter K. L. and Daniele Guinot and Peter J. F. Davie, 2008. Systema Brachyurorum: Part 1. An annotated checklist of extant Brachyuran crabs of the world. The Raffles Bulletin of Zoology. Supplement No. 17, 31 Jan 2008. 286 pp. (Online PDF on the Raffles Bulletin of Zoology website).
• Lim, S., P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life and Times of Labrador Beach. Division of Biology, School of Science, Nanyang Technological University & Department of Zoology, the National University of Singapore. 160 pp.
• Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore. National Council on the Environment. 163pp.
• Ng, P. K. L. & Y. C. Wee, 1994. The Singapore Red Data Book: Threatened Plants and Animals of Singapore. The Nature Society (Singapore), Singapore. 343 pp.
• Jones Diana S. and Gary J. Morgan, 2002. A Field Guide to Crustaceans of Australian Waters. Reed New Holland. 224 pp.