Crab vs. Lobster

Crab and lobster are marine invertebrates that belong to the group of crustaceans. There are around 6800 species of crab that inhabit fresh and marine water and terrestrial ecosystems. Crabs can be found all over the world. They are especially abundant in subtropical and tropical areas. Lobsters are less diverse group of animals. There are around 48 species of lobster that can be found in the oceans (and occasionally brackish water) around the world, except in the polar regions. They spend their life on the sandy, rocky or muddy sea floor, usually near the coast or on the edge of continental shelf. Crabs and lobsters are very popular seafood. Aside from similar habitat, they do not have much in common. They differ in:

Size

Crabs can be miniature (less than an inch in diameter) or very large (leg span of 13 feet). Most species are few inches wide. Lobsters are generally larger than crabs. They are usually 10 to 20 inches long, but some species can reach 3.25 feet in length and around 44 pounds of weight.

Morphology

Lobsters have elongated body covered with light-weight exoskeleton. They have 5 pairs of legs. First pair of legs is modified into very large claws. Lobsters either walk slowly on the seafloor or swim backward by curling and uncurling their abdomen. Bogy of crabs is covered with large carapace. Crabs have roundish (females) or triangular-shaped (males) abdomen, thick exoskeleton, 4 pairs of legs and one pair of claws called chelae. Claws are uneven in size in males, and used to attract females. Eyes are located on the long eyestalks. Some crabs are able to walk backward and forward, but most species walk sideways.

Tail and Antennas

Crabs have very short tail hidden under the thorax and small antennas. Lobsters have long, muscular tail with fan-shaped tip and very long antennas that function as sensory organs in the murky waters.

Diet

Both crabs and lobsters are omnivores. Crabs eat bacteria, fungi, algae and mollusks. Lobsters consume mollusks, worms, other crustaceans, fish and aquatic plants. They also eat their own skin after molting to preserve calcium in the body (calcium improves hardness of exoskeleton).

Lifestyle

Crabs are social creatures. They have complex behavior and communicate by waving and drumming their pincers. They aggressively protect their territories and fight for the attention of females or best caves and holes in the sea. Crabs cooperatively collect food for their family. Lobsters are solitary creatures. They usually live on their own, hidden under the rocks or in the burrows on the bottom of the sea.

Lifespan

Crabs can survive 8 to 13 years, while lobsters can survive around 70 years in the wild.