Cichlid
A diverse family of fish known for parental care and rapid speciation.
Cichlids are a large and varied family of percomorph fish, officially known as Cichlidae and placed in the order Cichliformes. Scientists have described at least 1,760 species, making this one of the biggest vertebrate families—only the Cyprinidae family has more named species. New cichlids are found every year, and many haven't been described yet, so the true total is unknown; estimates range from 2,000 to 3,000. These fish naturally occur in the Neotropics, Africa (including Madagascar), the Middle East, and the Indian subcontinent, though people have introduced some species around the world. Many cichlids, especially tilapia, are raised for food, while species like Cichla are popular game fish. Others, such as angelfish, oscars, and discus, are common in home aquariums. Among all vertebrate families, cichlids have the most endangered species, with most of these belonging to the haplochromine group. They are famous for evolving rapidly into diverse species flocks in Africa's Great Lakes, showing major differences in jaw and tooth structure, fin, head, and body shape, and especially coloration. This diversity makes them important for studying evolution. Some cichlids introduced outside their native range have become pests. All cichlids care for their eggs and fry, either by guarding them or by mouthbrooding.
The rapid speciation in Lakes Victoria, Malawi, and Tanganyika is partly due to their geological and climate history. Tectonic rifting about 20–25 million years ago created the rift system, eventually forming these lake basins. Lake Tanganyika, the oldest, formed around 12–9 million years ago, while Lake Malawi deepened later, during the Pliocene (roughly 5–2 million years ago). Sediment cores from Lake Malawi show that over the past 1.3 million years, the lake level dropped at least 24 times by 200 meters and 14 times by 400 meters; similar patterns appear in the other two lakes. These lowstands reduced available habitats and isolated fish populations, while highstands refilled the lakes, increased habitat, and reconnected populations, allowing hybridization and gene flow.
Cichlids vary greatly in size, from species as small as 2.5 cm (1 in), like female *Neolamprologus multifasciatus*, to nearly 1 m (3 ft) long, as in *Boulengerochromis* and *Cichla*.
Quick Facts
- Taxon
- Cichlidae
- Type Genus
- Cichla
- Type Genus Authority
- Bloch & Schneider, 1801
Facts from the source article.
Lore & Background
One of the reasons for rapid speciation in the African Great Lakes—Victoria, Malawi, and Tanganyika—is their geological and climate history. Tectonic rifting ~20–25 million years ago created the rift system, forming the lake basins. Lake Tanganyika formed ~12–9 million years ago, while Lake Malawi deepened during the Pliocene (~5–2 Ma). 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 lowstands reduced available habitats and isolated fish populations; highstands refilled the lake, reconnected populations, and allowed hybridization and gene flow. Cichlids span a wide range of body sizes, from 2.5 cm to 1 m, and exhibit diverse body shapes, from laterally compressed to cylindrical. They share a single key trait: the fusion of the lower pharyngeal bones into a single tooth-bearing structure, allowing a second set of jaws for processing food. This is assumed to be one reason for their diversity. All cichlids practice some form of parental care, usually guarding eggs and fry or mouthbrooding.
Reader's Guide
Cichlids are notable for their rapid evolution into morphologically diverse species flocks within the African Great Lakes, making them important for the study of speciation in evolution. Their diversity in jaw and teeth structure, fin, head, and body shape, and especially coloration, has been key to this. Many cichlids introduced outside their natural range have become nuisances. The family has the largest number of endangered species among vertebrate families, most in the haplochromine group. In taxonomy, cichlids were formerly classed in the suborder Labroidei within Perciformes, but molecular phylogenetics now supports a distinct order, Cichliformes, with the marine convict blenny as their closest living relative. The Catalog of Fishes places them in Cichliformes, part of the subseries Ovalentaria. The distribution of modern cichlids—Africa, Madagascar, the Neotropics, the Levant, southern Iran, and southern India—has been debated: whether it results from the breakup of Gondwana or more recent oceanic dispersal. Molecular clock estimates place the family's origin only to the Late Cretaceous, suggesting only dispersal can support modern distribution, though the factors enabling prehistoric cichlids to migrate across oceans remain a mystery.
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