Why do animals keep evolving into crabs?

By Laurel Hamers( lifes-little-mysteries ) published 3 days ago

Crabby bodies are so evolutionarily favorable, they've evolved at least five different times. So why does this process, known as carcinization, keep happening?



Crabs have flat, rounded bodies and a tail that's folded under the body. (Image credit: zahoor salmi via Getty Images)

A flat, rounded shell. A tail that's folded under the body. This is what a crab looks like, and apparently what peak performance might look like — at least according to evolution. A crab-like body plan has evolved at least five separate times among decapod crustaceans, a group that includes crabs, lobsters and shrimp. In fact, it's happened so often that there's a name for it: carcinization.

So why do animals keep evolving into crab-like forms? Scientists don't know for sure, but they have lots of ideas.

Carcinization is an example of a phenomenon called convergent evolution, which is when different groups independently evolve the same traits. It's the same reason both bats and birds have wings. But intriguingly, the crab-like body plan has emerged many times among very closely related animals.

The fact that it's happening at such a fine scale "means that evolution is flexible and dynamic," Javier Luque, a senior research associate in the Department of Zoology at the University of Cambridge, told Live Science.

More:
https://www.livescience.com/animals/crustaceans/why-do-animals-keep-evolving-into-crabs