Typical shape of members of the kelp crab family. Species in this family are usually from 5 to 9 cm across the carapace.
This week I bring you the “Where’s Waldo?” of the marine invertebrates. There is a decorator crab in each of the images at the link below. But first, here are some clues for you.
Most of the species of crabs that decorate themselves to be masters of camouflage are in the spider crab family (Majidae family – also known as “kelp crabs”). The image to the right shows you an undecorated kelp crab with the typical long legs and distinctly shaped shell (“carapace”) of this family.
Some crabs only partially camouflage themselves, especially when they are juveniles. Others “plant” so many marine neighbours onto themselves that you can’t tell them apart from their environment until they move.
Although they look like walking gardens, the organisms they attach to the stiff, curved hairs on their legs and backs are algae and animals, not plants. The animals can be soft corals, sponges or unique creatures like “bryozoans” and “hydroids”.
Not only does this covering of life allow the crabs to hide from predators, it also changes the way the crabs feel and taste. For example, sponges taste bad or are even toxic to many predators so, if you cover yourself with sponges, predators be gone! The bonus of carrying other organisms on your back is that you also have a food supply within a pincher’s reach.
It is truly astounding how well the decorator crabs match their immediate surroundings which added another mystery to my list: Is the range of decorator crabs really small so that they always match their background OR do they know to “adjust” their camouflage when they move to an area where they no longer blend in?
I have learned that the latter appears to be the case. Experiments with captive decorator crabs have shown that, if moved to a background that no longer offers camouflage, the crabs will “adjust” their decorations!
Click here to find the decorator crabs in my images or view gallery below.