Theraps is a genus of cichlid fish that includes only a single species, the Arroya ciclid (Theraps irregularis) from fast-flowing rivers and streams in the Usumacinta and Polochic basins of southern Mexico and Guatemala.[1][2] It is a medium-sized cichlid, up to 19 cm (7.5 in) in standard length.[3]
Historically, Theraps was included in Cichlasoma. Once recognized as its own genus, it sometimes included a wide range of species now known to belong in other genera, including Cincelichthys, Chortiheros, Chuco, Cryptoheros, Kihnichthys, Oscura, Paraneetroplus, Rheoheros, Talamancaheros, Tomocichla and Wajpamheros. In a major review of 2015, only five species remained in this genus,[4] but in 2016 it was shown that four of these were not close relatives of the Theraps type species, T. irregularis, resulting in them being moved to Chuco and Wajpamheros.[2] As a consequence, Catalog of Fishes now recognizes Theraps as only including the type species,[5] and as of 2023FishBase agrees.[3][update]