Periclimenes amethysteus
A rare little find on the French Riviera in cool 14-20C water, this tiny shrimp rewards divers who check every gorgonian closely.
A small, slender-bodied shrimp with a translucent to glassy body carrying patches of purple or amethyst colouring, which gives the species its scientific name. Look closely at gorgonians and other sessile invertebrates rather than scanning open water, since its size and see-through body make it easy to swim straight past. Long, thin walking legs and antennae are usually the first thing a diver's torch beam picks out before the body itself resolves.
Divers find this shrimp sitting still on host invertebrates such as gorgonians, relying on its near-transparent body to stay unnoticed rather than fleeing. It does not react much to divers at close range, which is exactly why a slow, careful look along sea fans and sponges pays off. Most sightings logged are one-off finds rather than repeat encounters at the same spot, consistent with its rare-to-uncommon status across sites.
It belongs to a genus of small, often host-specific shrimps that live in close association with a particular invertebrate, so finding the right host is usually the key to finding the shrimp.
There is not enough monthly sighting data to call a clear season, and the water temperature range logged (13.9 to 19.9C) spans much of the Mediterranean diving year, so treat it as a possible find whenever you are diving the French Riviera.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Every logged sighting of this shrimp so far comes from France, concentrated along the French Riviera and Provence coast. If you are diving that stretch of the Mediterranean, it is worth treating this as a French Riviera speciality rather than something to expect elsewhere.
Mapping where Shrimp Retainer is logged…
All confirmed sightings are from France, specifically along the French Riviera and Provence coast. It has not been logged elsewhere in current diver records, so treat it as a regional Mediterranean speciality.
There is no detectable seasonal pattern in the sightings, and the recorded water temperatures span 13.9 to 19.9C, covering much of the diving year on the French Riviera. It is best treated as a year-round possibility rather than a seasonal target.
Look for a small, mostly translucent shrimp with purple or amethyst patches on its body, sitting still on a gorgonian or similar host rather than swimming in open water. Its size and transparency make it easy to overlook, so slow, close searching of sea fans is the best approach.
Exact size data is not confirmed, but like most Periclimenes shrimps it is small, likely only a centimetre or two, and easily missed against its host.
No. It poses no risk to divers and is harmless to approach and photograph at close range.
It lives closely associated with a host invertebrate, most likely a gorgonian, relying on camouflage and stillness rather than fleeing when divers approach.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Freshwater Shrimp
2,168 sites
