Rediscovery of two critically endangered species of freshwater crabs, Afrithelphusa afzelii (Colosi, 1924) and A. leonensis (Cumberlidge, 1987) (Brachyura: Potamoidea: Deckeniidae) from the rainforests of Sierra Leone: implications for conservation

ABSTRACT The current status of two Sierra Leone Afrithelphusa freshwater crabs is unknown. Only two specimens of Afrithelphusa afzelii were collected ca. 1796 and given to Adam Afzelius from a single unknown Sierra Leone locality and the species is considered to possibly be extinct. The second species, A. leonensis, was described from three specimens: one from Sherboro Island and two presented to the Natural History Museum, London ca. 1955 from Sugar Loaf Mountain. This species, too, has not been reported since. Between January and February 2021, a survey of the rivers, streams, wetlands and nearby lowland humid rainforests of Sierra Leone collected fresh material from both these species. They were collected terrestrially in humid lowland forests, photographed live, details of their habitats are provided for the first time, and their conservation status is discussed. Immediate threats to these rare and critically endangered freshwater crabs and to the rainforest ecosystem upon which they depend include deforestation, agricultural encroachment, pollution, human predation and firewood gathering.