Eight millimeters of shrimp, living upside down under a sea urchin.
Its host is the burrowing urchin, which grinds itself a socket in the rock and sits in it with its spines fanned out, and the shrimp lives in the space that makes: under the urchin's body, among the bases of the spines, usually inverted with its back to the rock and its legs on the urchin. The spine canopy is a roof that moves with the tenant, and nothing that eats an eight-millimeter shrimp is going to reach in past it.
Finding one is a macro photographer's problem rather than a diver's. It is dark red with fine blue stripes, it is smaller than a grain of rice, and it is on the shaded underside of an animal covered in spines, so the only reliable method is to look into the base of the spines of urchin after urchin until something moves.
It is an alpheid, so it has the snapping claw, at a scale where the sound is a tick rather than a crack.
- eight millimeters long, dark red with bluish stripes
- usually upside down, walking on the underside of the urchin
- always with [Echinometra mathaei](/taxon/invertebrate/echinoderms/sea-urchin/burrowing-urchin), never in the open
- up to 0.8 cm
