Working Paper Hypothesis Version 2 This version is not peer-reviewed

How to Become a Crab: Phenotypic Constraints on a Recurring Body Plan

Version 1 : Received: 24 December 2020 / Approved: 25 December 2020 / Online: 25 December 2020 (13:31:09 CET)
Version 2 : Received: 1 March 2021 / Approved: 2 March 2021 / Online: 2 March 2021 (12:43:52 CET)

A peer-reviewed article of this Preprint also exists.

Journal reference: BioEssays 2021
DOI: 10.1002/bies.202100020


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.


Crustacea; Anomura; Brachyura; Carcinization; Phylogeny; Convergent evolution; Morphological integration


BIOLOGY, Anatomy & Morphology

Comments (1)

Comment 1
Received: 2 March 2021
Commenter: Joanna M. Wolfe
Commenter's Conflict of Interests: Author
Comment: Various minor edits in response to peer reviews, including addition of several references.
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