In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic interactions or opens new environmental niches. Starting with a single ancestor, this process results in the speciation and phenotypic adaptation of an array of species exhibiting different morphological and physiological traits. The prototypical example of adaptive radiation is finch speciation on the Galapagos, but examples are known from around the world.
Cichlids are fish from the family Cichlidae in the order Cichliformes. Traditionally Cichlids were classed in a suborder, the Labroidei, along with the wrasses (Labridae), in the order Perciformes, but molecular studies have contradicted this grouping. On the basis of fossil evidence, it first appeared in Tanzania during the Eocene epoch, about 46–45 million years ago. The closest living relative of cichlids is probably the 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. This family is large, diverse, and widely dispersed. At least 1,650 species have been scientifically described, making it one of the largest vertebrate families. 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.
Lake Malawi, also known as Lake Nyasa in Tanzania and Lago Niassa in Mozambique, is an African Great Lake and the southernmost lake in the East African Rift system, located between Malawi, Mozambique and Tanzania.
Lake Tanganyika is an African Great Lake. It is the second-oldest freshwater lake in the world, the second-largest by volume, and the second-deepest, in all cases after Lake Baikal in Siberia. It is the world's longest freshwater lake. The lake is shared among four countries—Tanzania, the Democratic Republic of the Congo (DRC), Burundi, and Zambia, with Tanzania (46%) and DRC (40%) possessing the majority of the lake. It drains into the Congo River system and ultimately into the Atlantic Ocean.
The terms shell dwellers or shelldwellers, shell-breeding, or ostracophil are descriptive terms for cichlid fish that use the empty shells of aquatic snails as sites for breeding and shelter. The terms have no taxonomic basis, although most shell-dwelling cichlids are from Lake Tanganyikas lamprologine lineage. Many shell dwelling cichlids are popular with fishkeepings and are frequently kept in aquaria.
Julidochromis is a genus of cichlids in the subfamily Pseudocrenilabrinae. They are commonly called julies and are endemic to Lake Tanganyika in eastern Africa. This genus includes six formally described species, some with a number local variants of uncertain taxonomic status. Further taxonomic work is required to determine how many species exist; the closely related Chalinochromis with two more species is sometimes included here and this may be correct. Hybridization makes attempts to determine relationships with molecular phylogenetic methods difficult.
Variabilichromis moorii has no common name and is a species of freshwater cichlid endemic to Lake Tanganyika in eastern Africa. It is a small ovate bodied fish named for an early collector of fish from the lake, John Edmund Sharrock Moore (1870-1947) who was a cytologist, zoologist and led an expedition to Lake Tanganyika and who discovered this species. Juveniles are usually yellow, and adults are dark brown to black in color. It reaches a total length (TL) of 10.3 centimetres (4.1 in). Currently it is the only member of its genus. V. moorii feeds on algae, zooplankton, and benthic invertebrates. It is also found in the aquarium trade.
Lamprologus ocellatus is a species of shell dwelling cichlid endemic to Lake Tanganyika. It is a popular aquarium fish due to its small size, appearance, and intelligence.
Paedophagy in its general form is the feeding behaviour of fish or other animals whose diet is partially, or primarily the eggs or larvae of other animals. However, P. H. Greenwood, who was the first to describe paedophagia, defines it to be a feeding behaviour evolved among cichlid fishes.
Lepidophagy is a specialised feeding behaviour in fish that involves eating the scales of other fish. Lepidophagy is widespread, having evolved independently in at least five freshwater families and seven marine families. A related feeding behavior among fish is pterygophagy: feeding on the fins of other fish.
Perissodus is a genus of cichlids endemic to Lake Tanganyika in Africa. They feed on scales.
Perissodus microlepis is a species of cichlid endemic to Lake Tanganyika. This species reaches a length of 11 centimetres (4.3 in) TL. This species can also be found in the aquarium trade. It is a scale-eating 'parasite' on other fish species. It occurs in two distinct morphological forms. One morph has mouth parts twisted to the left, enabling it to eat scales off its victim's right flank. In contrast, the other morph, whose mouth is twisted to the right, eats scales off its victim's left flank. The relative abundance of the two morphs in populations is regulated by frequency-dependent selection.
Plecodus elaviae is a species of cichlid endemic to Lake Tanganyika. This schooling species is a scale-eater, plucking scales from other fishes. Both parents care for the offspring in this mouthbrooder. This fish can reach a length of 32 centimetres (13 in) TL.
Plecodus is a genus of cichlids endemic to Lake Tanganyika in Africa. They feed on scales.
Plecodus straeleni is a species of cichlid fish that is endemic to Lake Tanganyika in East Africa. This species can reach a total length of 16 centimetres (6.3 in).
Lamprologini is a tribe of African cichlid fishes. It contains seven genera and nearly 100 species. Over half of the species in this tribe are in the large genus Neolamprologus. Most genera in the tribe are endemic to Lake Tanganyika, but one species of Neolamprologus is from the Malagarasi River in Tanzania, and several species of Lamprologus are from the Congo River Basin.
Tropheini is a tribe of African cichlids, endemic to Lake Tanganyika. The species in this tribe are mouthbrooders.
Cyprichromini is a tribe of African cichlids, containing seven species in two genera: Cyprichromis and Paracyprichromis. Most species are endemic to Lake Tanganyika; only C. microlepidotus has also been seen in eastern Tanzania.
Eretmodini is a tribe of African cichlids. It contains five species of freshwater fish endemic to Lake Tanganyika. They are small fish with reduced swim bladders that are found near the bottom in the turbulent, coastal surf zone. They are mouthbrooders.
Sargochromis is a genus of haplochromine cichlids native to freshwater habitats in Southern Africa, where found in the upper and middle Zambezi basin, Okavango delta, Cunene basin, Cuvelai basin and southeastern Congo Basin. They are typically known as happies or smallmouths. The latter name refers to their small mouth compared to their close relatives, the largemouths of the genus Serranochromis. Unlike the species in that genus which mostly feed on other fish, Sargochromis mostly feed on invertebrates, but in some species plant material is important. On occasion they will also eat small fish, and the stomachs of S. carlottae and S. codringtonii commonly contain fish scales, but whether these are already-lost scales that are picked off the bottom or they are actively bumped off large fish is unknown. Some of the species that feed heavily on aquatic snails have been used for biological pest control. Sargochromis are mouthbrooders. Depending on the exact species, they reach a maximum total length of 20 to 48 cm (8–19 in).
