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How do crustaceans become crabs?

Phylogenetic evidence from the author’s previous studies indicates that the carcinogenic body plan has evolved multiple times (indicated by the colored features of the branches). Baked clades are sponge crabs, “higher” real crabs, porcelain crabs, hairy stone crabs, and king crabs. The decarcinized clade shown is a frog crab. Credit: Joanna M. Wolfe

Crabs have recently lived a memetic life on social media. Memes are joking that everything will eventually look like a crab. But it is actually based on some truth.


The shape of the crab has evolved many times. Evolutionary biologist LA Borradaile coined the term carcinogenesis in 1916 to describe the process of convergent evolution in which crustaceans evolve from crab-like to crab-like. Crabs are decapod crustaceans of the Infraorder Bracula, considered “true crabs”, most of which are carcinogenic. “Crab” belongs to Infraorder Anomura. This group has evolved a crab-like body plan more than three times from its unfired ancestors.

In a paper published on March 12 BioEssaysA research team led by Harvard University has discovered that crab-like body plans have evolved at least five times independently in both true crabs (Brachyura) and fake crabs (Anomura). They also found that crab-like body plans were lost at least seven times in a process called cancer removal.

A team led by Joanna M. Wolfe, a postdoctoral fellow at Harvard University’s Department of Bioevolutionary Biology (OEB), examined a complex of crab phylogenetic data. They synthesized morphological data from major fossil and living crab groups, as well as data from behavior, natural history, functional morphology, and development, all from previous studies by the author.

Building a comprehensive dataset containing fossils and extant species that represent all crab families is important for identifying the key characters that define what a crab is. This allows you to resolve multiple origins and losses of the “crab” body. Formed over time, it identifies the timing of major evolutionary novelties and bodyplan origins. “

Carcinogenesis is characterized by a wide, flat shell (hard shell) and a folded preon (abdomen or tail). Unlike the visible lobster preon, the preon is primarily hidden under the crab’s body. Moulting causes the shell to become elongated. Preons are not bent, so they usually look and stretch. Dearsinization is an example of a group that re-evolves lost morphology and is considered a rare event in evolution.

“Biologists want to know how to’predict’whether a phenotype or morphology evolves within a group,” said Heather D. Blackengrissum, an associate professor at Florida International University. Says. “Examining the evolution of crabs gives us a timescale of a cataclysm of 250 million years ago. With sufficient phylogenetic and genomic data, we may be able to predict the resulting morphology.”

“Carcinogenesis can also compare the convergent evolution of fossil morphology with the convergent evolution of living organisms, but this is not yet common practice,” Wolff agreed.

Researchers are not entirely convinced, but believe that the common ancestor of Bracula and Anomura is likely not killed. “This evidence suggests that carcinogenesis actually evolved independently in these groups,” said Javier Luque, a postdoctoral fellow at Harvard University and the Smithsonian Tropical Research Institute.

Wolfe can now quantitatively characterize carcinogenesis by measuring the shape of existing crab specimens from the Harvard Museum of Comparative Zoology collection, in collaboration with Harvard University’s OEB assistant professor Javier Ortega-Hernández. I am testing the hypothesis.


Meet the newly discovered hermit crab, Heather Crab


For more information:
Joanna M. Wolfe et al, How to Become a Crab: Phenotypic Constraints on Repeated Body Plans, BioEssays (2021). DOI: 10.1002 / bies.202100020

Courtesy of Harvard University

Quote: How do crustaceans become crabs? (March 11, 2021) Obtained March 11, 2021 from https://phys.org/news/2021-03-crustacean-crab.html

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How do crustaceans become crabs?

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