This video gives an up close and personal view of a carrier crab with a sea urchin on its back. Carrier crabs are known for carrying almost anything on their backs for extra protection (even marine creatures). Their companions also benefit from the free ride on the crab’s back since they’re able to access new feeding grounds. Sea urchins are the ideal companion of carrier crabs because their bodies are covered in intimidating spikes.
In this instance, a carrier crab was filmed off the Indonesian coast carrying an Astropyga radiata (also known as a red urchin, fire urchin, or blue-spotted urchin). Researchers have found this choice of sea urchin strange because the red urchin is one of the most mobile urchins in the ocean. National Geographic grantee and researcher, Harilaos Lessios from the Smithsonian Tropical Research Institute, says, “I’ve never seen anything like this”.
Carrier crabs have two hind legs that are specially adapted for grabbing. They can easily grab ocean debris or a small marine creature that will become its new form of protection. In this video, the red urchin is not the only companion of the carrier crab; you’ll also see a group of cardinal fish swimming around the crab’s urchin shied, tagging along for the ride.