Cichlids () are a large, diverse, and widespread family of percomorph fish in the family Cichlidae, order Cichliformes. At least 1,760 species have been scientifically described, making it one of the largest vertebrate families, with only the Cyprinidae being more speciose. New species are discovered annually, and many species remain undescribed. The actual number of species is therefore unknown, with estimates varying between 2,000 and 3,000. They are native to the Neotropics, Africa (including Madagascar), the Middle East, and the Indian subcontinent, although some species have been introduced worldwide.Friedman, M., B. P. Keck, A. Dornburg, R. I. Eytan, C. H. Martin, C. D. Hulsey, P. C. Wainwright, et al. 2013. Molecular and fossil evidence place the origin of cichlid fishes long after Gondwanan rifting. Proceedings of the Royal Society B: Biological Sciences 280:20131733.
Many cichlids, particularly tilapia, are important food fishes, while others, such as the Cichla species, are valued game fish. The family also includes many popular freshwater aquarium fish kept by hobbyists, including the angelfish, oscars, and discus. Cichlids have the largest number of endangered species among vertebrate families, most in the haplochromine group. Cichlids are well known for their rapid evolution into morphologically diverse species flocks within the African Great Lakes. Some of these key morphological differences include jaw and teeth structure, fin, head, and body shape, and most importantly, their coloration.Santos, M. E., J. F. Lopes, and C. F. Kratochwil. 2023. East African cichlid fishes. Developmental Biology Advances 14:1.Kocher, T. D. 2004. Adaptive evolution and explosive speciation: the cichlid fish model. Nature Reviews Genetics 5:288–298. Their diversity in the African Great Lakes is important for the study of speciation in evolution. Many cichlids introduced into waters outside of their natural range have become nuisances.
All cichlids practice some form of parental care for their eggs and fry, usually in the form of guarding the eggs and fry or mouthbrooding.
History One of the reasons of rapid speciation in the African Great Lakes, Victoria, Malawi, and Tanganyika, is their geological and climate history. Tectonic rifting that occurred ~20–25 million years ago created the rift system, eventually forming the basins of the three lakes. Lake Tanganyika, the oldest, formed ~12–9 million years ago, while Lake Malawi deepened more recently during the Pliocene (~5–2 Ma).Santos, M. E., J. F. Lopes, and C. F. Kratochwil. 2023. East African cichlid fishes. Developmental Biology Advances 14:1. Sediment core analysis from 1.3 million years ago shows lake-level fluctuations, with at least 24 drops of 200m and 14 drops of 400m in Lake Malawi; these patterns are also seen in the other two lakes.Ivory, S. J., M. W. Blome, J. W. King, M. M. McGlue, J. E. Cole, and A. S. Cohen. 2016. Environmental change explains cichlid adaptive radiation at Lake Malawi over the past 1.2 million years. Proceedings of the National Academy of Sciences 113:11895–11900. Lyons, R. P., C. A. Scholz, A. S. Cohen, J. W. King, E. T. Brown, S. J. Ivory, T. C. Johnson, et al. 2015. Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity. Proceedings of the National Academy of Sciences 112:15568–15573. Danley, P. D., M. Husemann, B. Ding, L. M. DiPietro, E. J. Beverly, and D. J. Peppe. 2012. The impact of the geologic history and paleoclimate on the diversification of East African cichlids. International Journal of Evolutionary Biology 2012:1–20.
These patterns of lowstands reduced available habitats and geographically isolated fish populations; highstands refilled the lake, increased habitat availability, and reconnected populations, allowing hybridization and gene flow within the different fish populations.Irisarri, I., P. Singh, S. Koblmüller, J. Torres-Dowdall, F. Henning, P. Franchini, C. Fischer, et al. 2018. Phylogenomics uncovers early hybridization and adaptive loci shaping the radiation of Lake Tanganyika cichlid fishes. Nature Communications 9:3159. Koblmüller, S., W. Salzburger, B. Obermüller, E. Eigner, C. Sturmbauer, and K. M. Sefc. 2011. Separated by sand, fused by dropping water: habitat barriers and fluctuating water levels steer the evolution of rock-dwelling cichlid populations in Lake Tanganyika: climate-driven cycles of gene flow and isolation. Molecular Ecology 20:2272–2290.
Anatomy and appearance Cichlids span a wide range of body sizes, from species as small as in length (e.g., female Neolamprologus multifasciatus) to much larger species approaching in length (Boulengerochromis and Cichla). As a group, cichlids exhibit a similar diversity of body shapes, ranging from strongly laterally compressed species (such as Altolamprologus, Pterophyllum, and Symphysodon) to species that are cylindrical and highly elongated (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 similar to the North American sunfishes in morphology, behavior, and ecology.
Cichlids share a single key trait - the fusion of the lower pharyngeal bones into a single tooth-bearing structure. A complex set of muscles allows the upper and lower pharyngeal bones to be used as a second set of jaws for processing food, allowing a division of labor between the "true jaws" (mandibles) and the "pharyngeal jaws". Cichlids are efficient and often highly specialized feeders that capture and process a very wide variety of food items. This is assumed to be one reason why they are so diverse.
Taxonomy
Internal taxonomy The following consensus taxonomy is based on the Catalog of Fishes (2025)
Family Cichlidae Bonaparte, 1835 Subfamily Etroplinae Kullander, 1998 (Indian and Madagascan cichlids) Subfamily Ptychochrominae Sparks, 2004 (Malagasy cichlids) Subfamily Pseudocrenilabrinae Fowler, 1934 (African cichlids) Subfamily Cichlinae Bonaparte, 1835 (American cichlids)
In the past, cichlid taxonomy has varied depending on the author. Kullander (1998) recognized eight subfamilies of cichlids: the Astronotinae, Cichlasomatinae, Cichlinae, Etroplinae, Geophaginae, Heterochromidinae, Pseudocrenilabrinae, and Retroculinae. A ninth subfamily, the Ptychochrominae, was later recognized by Sparks and Smith. Cichlid taxonomy is still debated, and classification of genera cannot yet be definitively given. A comprehensive system of assigning species to monophyletic genera is still lacking, and there is not complete agreement on what genera should be recognized in this family.
As an example of the classification problems, Kullander placed the African genus Heterochromis phylogenetically within Neotropical cichlids, although later papers concluded otherwise. Other problems center upon the identity of the putative common ancestor for the Lake Victoria superflock (many closely related species sharing a single habitat), and the ancestral lineages of Lake Tanganyikan cichlids.
Phylogeny derived from morphological characters shows differences at the genus level with phylogeny based on genetic loci. A consensus remains that the Cichlidae as a family are monophyletic.
In cichlid taxonomy, dentition was formerly used as a classifying characteristic, but this was complicated because in many cichlids, tooth shapes change with age, due to wear, and cannot be relied upon. Genome sequencing and other technologies transformed cichlid taxonomy.
Alternatively, all cichlid species native to the New World, can be classified under the subfamily Cichlinae, while Etroplinae can classify all cichlid species native to the Old World.
External taxonomy The taxonomic placement of cichlids has long been disputed and variable, and has only recently been largely resolved. In the past, based on morphological characteristics, cichlids were classed in a suborder, the Labroidei, along with the wrasses (Labridae), in the order Perciformes. However, studies incorporating molecular phylogenetics have contradicted this grouping.
More recent phylogenetic studies support the creation of a distinct order, the Cichliformes, to contain the cichlids and their close relatives, which are no longer thought to be closely related to wrasses. The closest living relative of cichlids has been found to be the marine convict blenny, and both families are classified in the 5th edition of Fishes of the World as the two families in the Cichliformes, part of the subseries Ovalentaria. The Catalog of Fishes adopts the same placement, although the leaffishes (which have a similar African and South American distribution) are now also placed in the Cichliformes. Although these interrelationships are now generally well-supported, other authors have interpreted these relationships in differing ways, such as instead placing the cichlids, leaffish, and convict blenny as the most basal members of an expanded Blenniiformes.
Evolution Modern cichlids have a disjunct distribution consisting of Africa (including Madagascar), the Neotropics (including Cuba and Hispaniola), the Levant, southern Iran, and the southern Indian subcontinent. This distribution has become the subject of much scientific dispute, with it being debated whether modern cichlid distribution is a consequence of the breakup of Gondwana (which would make cichlids a particularly ancient group dating to the Early Cretaceous), or if it is instead based on more recent oceanic dispersal by the cichlids (despite modern members of the group being largely restricted to freshwater).
Proponents of the Gondwanan theory, which saw more support in the past, have noted that the cichlids display the precise sister relationships predicted by Gondwanan distribution: Africa-South America and India-Madagascar, and that with the exception of the species from Cuba, Hispaniola and Madagascar, cichlids have not reached any oceanic island. The dispersal hypothesis, in contrast, requires cichlids to have negotiated thousands of kilometers of open ocean between India and Madagascar without colonizing any other island, or for that matter, crossing the Mozambique Channel to Africa.
However, more recent studies incorporating phylogenetic evidence have found that the divergences within the cichlids are far too young for cichlids to have even been present for the breakup of Gondwana. Molecular clock estimates have placed the family's origin only to the Late Cretaceous period, and the divergences within the family to have occurred anywhere between the Late Cretaceous to the Eocene (depending on the study). This suggests that only dispersal can support modern cichlid distribution. However, the factors that may have allowed prehistoric cichlids to make migrations over entire oceans remains a mystery. It is known that during the Paleogene, the Atlantic Ocean between South America and Africa was significantly narrower, and it has been suggested that either now-submerged islands or a large plume from the Congo River may have allowed for a shallower or less saline environment that was conducive for cichlids to disperse from Africa to South America. Under the dispersal hypothesis, it is generally accepted that Africa was the ancestral home for cichlids, from which they dispersed to attain their present distribution.
Fossil record