The Evolutionary Mystery of Crab-Like Animals.

The crab-like body plan has evolved at least five separate times among decapod crustaceans, a group that includes crabs, lobsters and shrimp. This phenomenon is called carcinization, an example of convergent evolution. Scientists have many ideas but are not sure why animals keep evolving into crab-like forms. The crab-like body plan has emerged many times among very closely related animals, indicating that evolution is flexible and dynamic. The crab body plan might leave more flexibility for animals to evolve specialized roles for their legs beyond walking, allowing crabs to easily adapt to new habitats.