How Many Legs Does a Dungeness Crab Have?

The Dungeness crab (Metacarcinus magister) is a highly valued crustacean recognized for its sweet meat along the North American Pacific coast, from Alaska down to California. Like all true crabs, its body structure is protected by a hard exoskeleton. Understanding the number and arrangement of its appendages provides insight into its life as a bottom-dwelling scavenger.

Counting the Appendages

The Dungeness crab, like all members of the order Decapoda, possesses ten thoracic appendages, giving the group its name, which translates to “ten feet.” These ten limbs are arranged in five distinct pairs that attach to the cephalothorax, the fused head and chest region. The foremost pair is the claws, scientifically known as chelipeds. These large pincers are used for defense and feeding. The remaining four pairs are the true walking legs, or pereiopods.

How Crabs Use Their Legs

The chelipeds are highly specialized organs of offense and defense, used to deter predators and engage in aggressive interactions with rivals. One claw is often slightly larger than the other, demonstrating dimorphism. The larger claw acts as a powerful crusher, used to break open the hard shells of prey like clams and mussels. The smaller claw is employed as a cutter for more precise tasks, such as tearing apart food or grooming.

The four pairs of pereiopods are dedicated to navigating the ocean floor. These walking legs allow the crab to scuttle sideways across sandy or muddy substrates. Their pointed tips also assist the crab in burrowing into the sediment to find refuge. The legs collectively provide stability and balance.

Identifying the Dungeness Crab

The Dungeness crab is identifiable by its broad, oval-shaped carapace. The shell color ranges from reddish-brown to yellowish-brown, sometimes featuring purple tints, with a lighter, yellowish underside. A distinguishing feature is the serrated, or saw-toothed, edge found along the front sides of the carapace. This edge has ten distinct teeth on each side of the area between the eyes. Adult Dungeness crabs are relatively large, with the carapace commonly reaching a width of 8 to 10 inches. They prefer to inhabit sandy or muddy bottoms in coastal waters, ranging from the intertidal zone down to significant depths.

Written by

Katarina Visser

Coral reef ecologist Katarina Visser earned her PhD in marine biology at James Cook University in Australia. Over 14 years of research diving in the Indo-Pacific and Caribbean, she has studied mass bleaching, reef recovery after marine heatwaves, and how fish communities change inside marine protected areas. She has coordinated long-term reef monitoring surveys for a university research station. Her writing covers corals, reef fish and invertebrates, and what ocean warming means for reef ecosystems.