Mithraculus forceps
Tucked into reef crevices around Portsmouth, Dominica, this small reef crab is an uncommon but steady find in 25-31°C Caribbean water.
Small crab, only a few centimetres across the carapace, with a rounded, slightly flattened shell marked by faint reddish or purplish ridges running across its back. Legs are typically pale to olive, giving a mottled, hard-to-spot look against rubble and coral rock. The claws are stout but not oversized, and the whole animal sits low and tight against the substrate rather than perched in the open.
Divers typically find it wedged into crevices, under coral ledges, or tucked among rubble and algae, staying still rather than scuttling into the open. It's an uncommon-to-rare find even where it's known to occur, so spotting one usually comes down to a slow, close look at reef nooks rather than scanning open water. Largely inactive by day, it tends to stay put when a torch or camera gets close rather than bolting.
Like other Mithraculus crabs, it's an opportunistic grazer that picks at algae and detritus on the reef, making it a minor but steady part of the reef's cleanup crew.
No clear seasonal pattern shows up in the sightings, and with water in the 25-31°C range year-round across its Caribbean sites, it's a good bet on any dive regardless of month.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most reliably logged around Portsmouth, Dominica, which accounts for the bulk of sightings, with a smaller but steady presence off Saint John in the US Virgin Islands. A single Bermuda record shows it turns up outside the core Caribbean range too, though far less often.
Mapping where Red-ridged Clinging Crab is logged…
It's most consistently seen around Portsmouth, Dominica, with additional sightings off Saint John in the US Virgin Islands and an occasional record from Bermuda.
There's no strong season in the sightings data. Warm water sits between 25 and 31°C year-round across its range, so it's findable on any dive month to month.
Look for a small, rounded crab with faint reddish ridges across the carapace, wedged tight into a crevice or rubble patch rather than out in the open. Its mottled pale-to-olive legs and low profile make it easy to miss unless you look closely.
It's a small reef crab, generally only a few centimetres across the carapace, easy to overlook against rubble and coral rock.
No. It poses no threat to divers and will typically just stay still or retreat further into its crevice if approached.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Sally Lightfoot Crab
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