About Mithraculus cinctimanus Stimpson, 1860
Mithraculus cinctimanus is a small crab with an oval carapace that is slightly longer than it is wide. The front third of the carapace is slightly hairy, and the surface of the rear two thirds is roughened by small tubercles. The front edge of the carapace has several blunt spines. The colour of the carapace is variable, and it is often olive brown with several large creamy patches. The legs have bands of these same colours, and their outer segments are hairy. The fingers of the chelae do not completely close and have rounded tips. Full-grown adult Mithraculus cinctimanus reach about 22 millimetres (0.87 in) in length. This species is distributed across the Caribbean region, with a range that includes Florida, the West Indies, Curaçao, Colombia, and Venezuela. Mithraculus cinctimanus typically lives commensally with a sponge, coral, or sea anemone. Its common hosts include the sun sea anemone Stichodactyla helianthus in shallower waters, and the anemone Lebrunia danae in deeper waters. When living on Lebrunia danae, Mithraculus cinctimanus is part of a community of commensal invertebrates, each of which occupies its own distinct characteristic position on the host. This crab hides under the rim of the anemone's extended pseudotentacles; when the pseudotentacles retract, the crab also retreats, leaving only its chelae, eyes, and the front portion of its head exposed. The crab rarely moves far from its host anemone, and appears to be immune to stings from the host's nematocysts.
