Zenopontonia rex is a robust shrimp growing to a length of about , with females being rather larger and slightly less colourful. The antennae are modified into a series of plates that extend forwards from the head, and the
rostrum has a crest-like extension. The cephalothorax bears a small spine on either side. The first two pairs of legs bear pincers with short sensory hairs. The basic colour of this shrimp is orange-yellow to orange-red, with purple antennal plates, claws and walking legs. However, during the day, white
chromatophores in the skin expand and may cover much of the dorsal surface and tail fan; in other instances, the white colour appears as a median band, and the basic orange colour is revealed elsewhere. The colouring also varies depending on the shrimp's host; the classic colouring usually occurs when it is associated with a sea cucumber, but it sometimes matches the colour of its host, particularly when associated with an
opisthobranch. ==Distribution and habitat==