Identification: flattened, disc-shaped reddish-brown carapace with bluish veins, about 3 to 4 cm wide; legs ringed with yellow at the joints, with a row of spines along the leading edge; short antennae that constantly flick. Leg span about 10 cm. The name 'Sally Lightfoot' is also given to Grapsus grapsus, another species: check the scientific name when buying.
In the wild it lives in the western Atlantic (Florida to Brazil), the eastern Atlantic (Madeira to the Gulf of Guinea) and on the Pacific coast of the Americas, in rock crevices of the infralittoral zone and among algae-covered rubble. In the Caribbean it is associated with the sea urchin Diadema antillarum. First recorded in the Mediterranean in 1999 at Linosa (Sicily), it has spread from the Balearics to Greece, Turkey, Libya and Israel: it is one of the most invasive decapods in the Mediterranean, where it lives mostly among boulders. The rock goby Gobius paganellus is one of its predators.
Reproduction: egg-carrying females have been caught off West Africa from February to April and in August; the planktonic larvae are long-lived, which probably helps its spread. No source consulted describes captive breeding.
Status: the species has not been evaluated by the IUCN and is not listed by CITES; it appears on the IUCN black list of invasive marine species in the Mediterranean.
