The emperor shrimps, Periclimenes imperator, and Periclimenes soror, are a species of shrimp with a wide distribution across the Indo-Pacific. It lives commensally on a number of invertebrate hosts, including nudibranchs, sea cucumbers, and sea stars. Periclimenes imperator has typical duck-billed appearance and has purple legs and pinces. Periclimenes soror on the other hand is smaller and and its claws aren’t purple tipped. I’ve usually seen this species on blue sea stars in New Caledonia.