Zenopontonia rex

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Arthropoda · Class: Malacostraca · Order: Decapoda · Family: Palaemonidae · Genus: Zenopontonia.

Accepted name: Zenopontonia rex · Authority: (Kemp, 1922) · Taxonomic status: accepted · AphiaID: 871470.

Synonyms and superseded combinations recorded for this taxon: Periclimenes (Periclimenes) rex Kemp, 1922; Periclimenes imperator Bruce, 1967; Periclimenes rex Kemp, 1922.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=871470 (CC BY 4.0). Accessed 2026-09-23.

Biology and life history (SeaLifeBase)

Measured values published by SeaLifeBase for Zenopontonia rex. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Habitat zone: reef-associated.

Source: SeaLifeBase species summary (SpecCode 18874) — https://www.sealifebase.se/summary/Zenopontonia-rex.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.

Distribution and occurrence records (GBIF)

710 georeferenced occurrence records for Zenopontonia rex are published through GBIF from 31 countries or marine areas. The map above plots 115 distinct locations from a sample of 710 records, omitting 28 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: Indonesia (330); Philippines (124); Chinese Taipei (37); New Caledonia (34); Australia (31); Papua New Guinea (25); United States of America (23); Fiji (12); Malaysia (12); Israel (8); Japan (8); Madagascar (8); Marshall Islands (6); Solomon Islands (6); French Southern Territories (6).

Source: GBIF Occurrence Search (taxonKey 8539440) — https://www.gbif.org/occurrence/search?taxon_key=8539440&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=871470 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-23.

Description and natural history (Wikipedia)

Zenopontonia rex is a robust shrimp growing to a length of about 3 cm, 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.

Zenopontonia rex is native to the tropical Indo-Pacific region. Its range extends from the Red Sea, Réunion and Mayotte to Hawaii and French Polynesia, and from southern Japan to New Caledonia and northern Australia. It is found at depths down to about 40 m, always living in association with a large sea cucumber, a nudibranch or other large mollusc, perching on its back as its host moves around. It lives commensally on a number of hosts, including the sea slug Hexabranchus.

Zenopontonia rex lives as a commensal on sea cucumbers such as Bohadschia, Opheodesoma, Stichopus, Synapta maculata or Thelenota, or on nudibranchs and other large molluscs including Asteronotus, Ceratosoma, Chromodoris, Cypraea, Dendrodoris, Hexabranchus, Hypselodoris and Pleurobranchus; occasionally it has been observed living in association with a starfish such as Echinaster or Gomophia. There is often a pair of shrimps, or even three, on a single host, and then they usually have identical colouring. They keep to the dorsal surface or flanks, moving to the far side of the host if danger threatens. The shrimp feeds on detritus on the seabed, as well as cleaning the surface of its host and feeding on mucus and faeces. This species is gonochoric; the male uses his first two pairs of walking legs to deposit sperm on the underside of the female's thorax, where the eggs are incubated until they hatch. The larvae are planktonic.

Recent studies have shown that the emperor shrimp display predatory habits. Such as in two occasions in Tulamben, Bali, Indonesia. In the first case, a single shrimp lived in associated with C. tenue when it attacked a small palaemonid shrimp. The second case involved two shrimps that lived symbiotically with the echinasterid sea star when it attacked a small post-larval fish. This showed that in occasions the Z. rex claws are strong enough to grip relatively large prey, they are actively searching for prey, and they are an opportunistic hunter.

It' lives in water up to 45 m in depth, and can grow to a length of 1.9 cm.

A. J. Bruce first described it in 1967 based on eight specimens ranging from 4 mm to 7.6 mm.

Source: Wikipedia: Zenopontonia rex — https://en.wikipedia.org/wiki/Zenopontonia_rex (CC BY-SA 4.0). Accessed 2026-09-23.