The Emperor shrimp (Periclimenes imperator) is a species of shrimp with a wide distribution across the Indo-Pacific. It lives commensally on a number of hosts, including the sea slug Hexabranchus.[2] A. J. Bruce first described it in 1967 based on eight specimen ranging from 4 millimetres (0.16 in) to 7.6 millimetres (0.30 in), and found Periclimenes rex to be its best resemblance. Emperor shrimps live in waters up to 45 metres (148 ft) in depth[4], and can grow to a length of 1.9 centimetres (0.75 in).