Scientists are baffled as to why animals continue to evolve into crabs.


Scientists are baffled as to why animals continue to evolve into crabs.

True, crabs keep showing up in nature, and it’s causing so much consternation among scientists that they’ve been awarded federal money to figure out what’s going on.

Carcinization, a term that has been in use for almost 140 years, has been coined to describe the phenomenon. Crabs, the seashore bugs we all know and love, have evolved at least five times from different kinds of crustaceans, according to The Washington Newsday.

These two groups shared a common ancestor 300 million years ago. That means there has been plenty of time for evolution, but the crabs continue to arrive.

“Carcinization can be defined as the evolutionary process that leads to the crab-like appearance,” said Heather Bracken-Grissom, an associate professor at Florida International University’s Institute of Environment and Department of Biological Sciences who has been researching the phenomena.

“We know it’s happened before, and our current grant is geared at better understanding the drivers and consequences.”

In the technical sense, not all species that have undergone carcinization have become crabs. Some have simply morphed into crabs, taking on their shape and form. True crabs, or Brachyura, and false crabs, or Anomura, are the two primary groupings of carcinized species.

But it begs the question: what is it about the crab shape that attracts organisms to try to imitate it?

Joanna Wolfe, a researcher at Harvard University’s Department of Organismic and Evolutionary Biology, has been investigating this.

She told The Washington Newsday that “at least five genera of decapod crustaceans have evolved a crab-like body structure.” Most eubrachyurans, which include most land crabs, sponge crabs, porcelain crabs, king crabs, and the hairy stone crab, fall under this category.

So, what causes these critters to be so crabby? Carcinization entails developing crab-like traits such as a flattened, frequently spherical carapace (top shell) and a pleon (abdomen) that is folded under the body, according to Wolfe.

Looking for an Explanation

Another question is why they do it. “We’re still not sure,” Wolfe remarked. “Because the pleon is folded under the body, predators have a harder time catching it. Crabs may be better at squeezing into tight spaces to conceal. They might be able to move more quickly with the. This is a condensed version of the information.


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