Allopetrolisthes spinifrons
Allopetrolisthes spinifrons is a species of porcelain crab. It displays "hypercarcinisation", whereby the resemblance to a true crab is enhanced by sexual dimorphism of the abdomen. It lives along the Pacific coast of Peru and Chile, as a symbiont of a sea anemone. Description Allopetrolisthes spinifrons grows to a maximum carapace length of around . It displays an extreme form of carcinisation – evolution of a crab-like form – referred to as "hypercarcinisation". In contrast to other porcelain crabs, A. spinifrons shows sexual dimorphism of the pleon (abdomen), closely resembling the situation in true crabs. Females have a large pleon, similar to that of other porcelain crabs, covering almost all of the sternum. Males have a short, triangular pleon that only covers a small part of the sternum. A. spinifrons also differs from its relatives in having many fewer and smaller spines on its legs. These morphological differences are thought to be a consequence of the species' ecology, living in close association with a sea anemone, where the ability to escape by swimming is not needed. Distribution and ecology Allopetrolisthes spinifrons is found in the eastern Pacific Ocean, from Isla San Lorenzo, Peru to San Vicente, Chile, at depths of