Cichlids are fishes from the family Cichlidae in the order Perciformes. The family Cichlidae, a major family of perciform fish, is both large and diverse. Estimates of the number of cichlid species range from 1,900 to 2,200, making it one of the three largest vertebrate families. Cichlids span a wide range of body sizes, from species as small as 2.5 centimetres (1.0 in) in length (e.g. Neolamprologus multifasciatus ) to much larger species approaching 1 metre (3 ft) in length (e.g. Boulengerochromis and Cichla). As a group, cichlids exhibit a similarly wide diversity of body shapes, ranging from strongly laterally compressed species (such as Altolamprologus, Pterophyllum, and Symphysodon) through to species that are cylindrical and highly elongate (such as Julidochromis, Teleogramma, Teleocichla, Crenicichla, and Gobiocichla). Generally, however, cichlids tend to be of medium size, ovate in shape and slightly laterally compressed, and generally very similar to the North American sunfishes in terms of morphology, behaviour, and ecology. Many cichlids, particularly the tilapias, are important food fishes, while others are valued game fish (eg. Cichla species). Many species, including the angelfish, oscars, and discus, are also highly valued in the aquarium trade. Cichlids are also the family of vertebrates with by far the highest number of endangered species, most of these being from among the haplochromine group. Cichlids are particularly well known for having evolved rapidly into a large number of closely related but morphologically diverse species within large lakes, particularly the African Rift Valley lakes of Tanganyika, and Victoria, and Malawi. The diversity of cichlids in the African Great Lakes is important for the study of speciation in evolution. Many cichlids that have been accidentally or deliberately released into freshwaters outside of their natural range have become nuisance species, for example tilapia in the southern United States.
