Hermit crabs house hunt

Hermit crabs are clever creatures always on the lookout for a new home

Hermit crabs don’t have shells of their own but their soft abdomen is curved in a spiral that makes it a snug fit for the shells of gastropod molluscs, like sea snails. They have to regularly upgrade to a larger shell as they grow but they save themselves the considerable metabolic cost of hardening their own exoskeleton. Some of the borrowed shells gain an extra layer of protection in the form of sea anemones that attach to the outside. The anemone feeds on scraps dropped by the crab and in return, its stinging tentacles keep predatory fish away. One species of hermit crab even uses colonies of encrusting coral-like bryozoans to extend the size of its shell. This clever subcontracting arrangement gives the crab the advantages of a living shell, without the expense of building it.

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Some hermit crabs even make use of discarded lids or glass jars found under the sea. Although it’s not ideal, it’s certainly resourceful.



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Photograph: jenny downing


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Image from www.flickr.com/photos/stuutje