Lives in pairs on fire urchins, clearing a patch of spines to sit in.
A small palaemonid shrimp, reaching about 2 cm, living obligately on fire urchins. It was described from Asthenosoma intermedium in Queensland and is almost always photographed on the Pacific fire urchin Asthenosoma varium, though no published source confirms that host. The body is translucent cream to white, marked with large irregular blotches of deep purple-red, and the walking legs and tail fan are banded in the same colour. Within its habitat confusion is unlikely: it is the only shrimp of this pattern found on fire urchins. The unrelated Zenopontonia soror, which occupies sea stars, carries a superficially similar blotched pattern and is the species most often mistaken for it in photographs.
Almost always found as a mated pair, a larger female accompanied by a smaller male. The pair clears a patch of the urchin’s spines and pedicellariae, leaving a bare depression on the test in which they sit; that cleared patch is usually visible from further away than the shrimps themselves and is the practical way to find them. Recorded between roughly 5 and 30 m on sand and rubble slopes wherever the host occurs. A single urchin often carries other associates at the same time, including the zebra crab Zebrida adamsii.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.