How to become a crab: Phenotypic constraints on a recurring body plan

A fundamental question in biology is whether phenotypes can be predicted by ecological or genomic rules. At least five cases of convergent evolution of the crab-like body plan (with a wide and flattened shape, and a bent abdomen) are known in decapod crustaceans, and have, for over 140 years, been known as carcinization. The repeated loss of this body plan has been identified as decarcinization. In reviewing the field, we offer phylogenetic strategies to include poorly known groups, and direct evidence from fossils, that will resolve the history of crab evolution and the degree of phenotypic variation within crabs. Proposed ecological advantages of the crab body are summarized into a hypothesis of phenotypic integration suggesting correlated evolution of the carapace shape and abdomen. Our premise provides fertile ground for future studies of the genomic and developmental basis, and the predictability, of the crab-like body form.

Automated summary

The article discusses the evolutionary history of the crab body plan and the degree of phenotypic variation within crabs, proposing ecological advantages of the crab body and a hypothesis of phenotypic integration. This provides a foundation for future research on the genomic and developmental basis of the crab-like body form.