I’m watching a rock shaggy with algae and mud and debris. I’m watching it eat. I’m watching it move. I’m watching it freeze solid when I slip my hand in the water. I look carefully through the water and pick out 6 more rocks that are not rocks. The cove is littered with rocks, both of ones that eat and ones that don’t. The rocks that eat are decorator crabs. This one is Libinia emarginata.
A decorator crab wouldn’t be get caught dead without wearing the ocean’s latest fashion. Actually, yes it would. Decoration for this crab not about fashion but survival. The more it looks like that rock or that coral or that plant over there the more it can rest easy that it won’t be on someone’s dinner plate. It just can’t help that it looks fabulous. All the time. This is a crab of confidence. One must be confident if it’s your clothes that determine whether you eat or get eaten. How might fashion be shaped if we judged outfits based on whether or not the model got scarfed up by a predator at the end of the runway? A new ‘reality’ show? (I’ll leave it to you to come up with a clever title for this new reality show. Go ahead, whisper you clever little gem to me.)
Decorator crabs are found in variety of habitats including kelps, estuaries, and corals and use whatever’s available to be en vogue. It is a major fashion faux pas to show up to a new event in a new habitat wearing old clothes. A crab placed in a new habitat will shed its old outfit and immediately use local materials to blend in (even an aquarium full of pearls and lace – see video below; called a ‘dresser crab’ by the British). A bit of shaggy algae here, a dab of lace there.
The decorator crab I’ve been watching is also known as a spider crab. All decorator crabs are spider crabs, but not all spiders are decorators. This family brags not only the most fashionable crabs, but also the largest – the 12-foot Japanese spider crab, Macrocheira kaempferi. This crab is not a decorator crab. Perhaps when you’re more leg than body and can stretch up to a second story window (if you’re on your crab tippy toes), then you are either not worried about being someone’s dinner or perhaps you don’t think you’d make a convincing plant.
Japanese spider crab, Image courtesy of dailymail.co.uk