They are large and slow-growing, and are threatened by habitat loss, overexploitation by local people and by spread of introduced non-indigenous marbled crayfish (Procambarus virginalis).

They belong to the Gondwana-distributed family Parastacidae, but their nearest relatives live in Australasia, there being no native crayfish in mainland Africa or India.

The importance of habitat loss may have been underestimated in the past because most studies have focussed on the Ranomafana National Park, where the forests are largely intact but crayfish are still harvested by local people.

[5][6] Crayfish are only found in a relatively small area of Madagascar, covering parts of Toamasina, Antananarivo, Fianarantsoa and Toliara provinces; the total area they inhabit is around 60,000 square kilometres (23,000 sq mi) and ranges from the Isaha valley south to the Hauts Plateaux (near Anjozorobe).

[4] In 1839, the French explorer-naturalist Justin Goudot returned from an expedition to Madagascar bearing specimens of a crayfish he had collected there.

[2] Some years later, and apparently unaware of the two French descriptions, Charles Spence Bate published what he thought was the first account of Malagasy crayfish.

In their 1929 monograph, Théodore Monod and Petit recognised four "varieties", betsileoensis and madagascariensis (the "macrophthalmes") and brevirostris and granulimanus (the "microphthalmes").