The Cichlidae are a large family of freshwater fishes found in S. America (except for the cool, temperate S.), Central America and N. to Texas, in Africa, Madagascar and Asia Minor and around the coastal regions of India and Sri Lanka (Wheeler, 1979). As a family it is remarkably successful having developed into a variety of forms and ways of life which allow various species to fill most of the living space available. In the East African Great Lakes they are particularly abundant and many endemic genera have evolved in each lake.
The body is normally perch-like, usually slightly compressed, occasionally very flattened as in the angelfishes. It and most of the head are covered with scales and the dorsal and anal fins have a series of spines in their front section continuous with the soft rays. The most obvious distinguishing feature amongst freshwater fishes is the single nostril on each side of the head. Apart from this and the long continuous dorsal fin all cichlid have pharyngeal (throat) teeth that assist in processing food and their lateral line is interrupted.
In general cichlids prefer still or slow flowing water with may hiding places; some are pronouncedly territorial. Most are generalized predators, but some, particularly in the Great African Lakes have specialized diets, for which their teeth and jaws are variously adapted. The cichlids exhibit many interesting variations in body-form to exploit their habitats. Some species are plankton-eaters, others feed on fish, invertebrates, algae and plant matter, while some specialize in eating molluscs, cichlid eggs or scales from other fishes. One species even habitually bites the eyes out of living fishes.
Their breeding habits exhibit many refinements. Many species are territorial, breeding in a cleaned nest which is guarded by one or both parents. Mouth brooding of eggs and young is the habit of many other forms, while several species nourish their young on the mucus secreted fro the parental skin.
Many are popular aquarium fishes; in the areas in which they are abundant some are valuable food fishes.
The species I studied with respect to their visual capabilities and form features were mostly haplochromine endemic species from Lake Victoria, more specifically from the Mwanza Gulf. Due to taxanomic reconsiderations, many of the studied haplochromine cichlids received new generic names. Although often mentioned to belong to the genus Haplochromis, some of them are now placed in the genus Astatotilapia (A. argens instead of H. argens), the genus Yssichromis (Y. pyrrhocephalus instead of H. pyrrhocephalus) and in the genus Pundamilia (P. nyererei instead of H. nyererei).
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