FASCINATING FACT

Is nature turning everything into crabs?

The term ‘carcinisation’ was first coined in 1916 by Zoologist, Lancelot Alexander Borradaile. It describes the process in which non-crab-like forms have, over time, evolved into crab-like forms. Borradaile explains that it is “one of the many attempts by Nature to evolve a crab.”

Currently, the best example of this is within the infraorder Anomura. These include hermit crabs (Coenobita), coconut crabs (Birgus spp.), king crabs (Paralithodes spp.) and porcelain crabs (Porcellanidae) – none of which are true crabs or are even closely related to crabs (Brachyura). Some are much closer related to lobsters and hermit ‘crabs’ and the internal anatomy of all these crab-like species are entirely different to true crabs. However, convergent evolution over time has meant that all these crustaceans are becoming more and more crab-like by the day.

Although ‘carcinisation’ only received an official term in the early 20th Century, the field of study had been running for over 100 years prior. This is largely why we still use common names that falsely term crab-like animals as ‘crabs’. Cases of convergent evolution are common within the animal kingdom. For example, the poison frogs (Dendrobatidae) of South America and the Mantella spp. of Madagascar. Other examples include the horned lizards (Phrynosoma spp.) of North America and the Thorny devil (Moloch horridus) of Australia. However, ‘carcinisation’ already appears to have affected a huge number of crustacean species and will undoubtedly produce more crab-like species over time.

What’s next?