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Decorator Crab

Decorator crabs are master camouflagers of the ocean, adorning their shell with bits of algae, sponges, and other debris to help hide from predators!

 

The term “decorator crab” describes many different species of spider crabs found worldwide. They get their name from their resourceful use of items to decorate their shell. Crabs will select algae, sponges, sea anemones, or other items they find around their habitat and fasten them to hooked bristles, called setae, on the back of its shell. This clever camouflage can serve multiple purposes. It helps the crab blend into its surroundings, camouflaging it from predators as well as from prey. Additionally, the adornments on its shell make the crab appear larger, which can also help to deter would-be predators. Some decorator crabs even use their algal decorations as a food source when other resources are low! 

Because decorated shells are so important for these crabs, they don’t want to waste their hard work! The hooked setae on the crab’s shell works a little bit like Velcro, allowing the crab to remove decorations and attach others if they choose. This also means that when the crab molts, it doesn’t have to leave its carefully collected accessories behind — it can take choice pieces from its old shell and reaffix them to its new one. As crabs age and grow larger, they may decorate less, since their size can become its own natural deterrent to predators.

 

 

Because decorator crabs are found around the world, each species may face its own threats and challenges to survival. However, like all ocean animals, they depend on healthy and abundant oceans to survive.

 

 

Protecting and restoring our oceans benefits wildlife around the world. By speaking up and working together, we can create real, measurable change for oceans and marine life. Learn more about Oceana’s campaigns to protect and restore marine biodiversity and abundance here.

 

 

  • Animal Diversity Web 
  • Sanka I, and Wicksten MK. (1980) Decorator Crabs. Scientific American, 242(2): 146-154. DOI:10.1038/scientificamerican0280-146 
  • Wicksten MK. (1993) A Review and a Model of Decorating Behavior in Spider Crabs (Decapoda, Brachyura, Majidae). Crustaceana, 64(3): 314-325. https://www.jstor.org/stable/20104855 

 

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