This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Today's offering of Halloween in the Deep takes a closer look at a crab we first met yesterday.
What makes this crab extraordinary, as one of the narrators points out, is that most hermit crabs live inside shells, as their name implies. There are over a thousand species, and most of them rely on re-purposing discarded snail shells into all-terrain recreational vehicles. Their bodies are so adapted to this that their backsides are soft and sometimes even shell-shaped.
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However, at times, finding an empty, intact shell of just the right size can prove difficult, and the crabs may get into fights (or even shell-exchange samba lines) over desirable shells. Solution? Make your “shell” a living organism that can grow right along with you, as the anemone-toting crab featured in the video above has done.
As with their hermit kin, these crabs’ bodies have become so adapted to this lifestyle that their third pair of legs has become tiny T. rex-like stubs that serve only one purpose: hold on to that anemone! With only two pairs of legs remaining, they walk, as the narrator points out, in a particularly creepy fashion.