This species of tiny crab (only growing to be an inch wide) is native to the Hawaiian islands. It's commonly called the pom-pom crab or boxer crab because of its habit of carrying a sea anemone around in each of its claws, these resembling pom-poms or boxing gloves. Its Hawaiian name is kūmimi pua, meaning "inedible flower crab". They live in shallow reefs on sand/gravel where they can easily camouflage.
These crabs have a mutualistic symbiotic relationship with the anemones they hold in each claw. The anemones are fed and the crab uses them for defense, courtship, and for catching food particles. If an anemone dies the crab will propagate the other by ripping it in half. Multiple species of anemones have been recorded as being used by the crabs but they can also carry other organisms like sponges and nudibranchs while they look for replacement anemones. In the aquarium they can be kept with peaceful fish and other non-aggressive invertebrates.