The family Cichlidae is one of the most speciose groups of vertebrates, encompassing at least 1,760 described species, with estimates suggesting the true number could be well over 2,000. These fish are native to freshwater ecosystems across a vast geographic range, including Africa, Central and South America, the Middle East, and the Indian subcontinent. The sheer number of species and their diverse habitats have led to trophic specialization, where cichlids have evolved to fill almost every available feeding niche. This evolutionary success is tied to a unique jaw structure that allows them to adapt their diets to a wide variety of food sources found in the wild.
Herbivory, Algivory, and Detritivory
A significant portion of the cichlid family sustains itself on plant matter, algae, and decomposing organic material found throughout their aquatic environments. True herbivory involves consuming larger aquatic plants, or even terrestrial vegetation that falls into the water. Species like Tilapia rendalli feed on higher plant material. These plant-eaters possess robust pharyngeal teeth used to process tough plant fibers, necessary for efficient digestion.
Algivory is widespread, especially among the rock-dwelling cichlids of the African Rift Lakes, known as Mbuna in Lake Malawi. These species, such as Petrochromis and Tropheus, are specialized grazers that feed on the Aufwuchs—a dense mat of algae, diatoms, and small invertebrates that grows on rocky substrates. Their mouths are adapted with scraping teeth, allowing them to effectively shear this layer off the rock surface.
Some algivorous cichlids are highly territorial and actively maintain “algal farms” on their defended patch of rock. Due to the low nutrient content of a purely plant-based diet, these herbivorous species have evolved extremely long gastrointestinal tracts to maximize nutrient absorption.
Many cichlids are also detritivores, consuming soft bottom deposits and fine particulate organic matter found in the substrate. This detritus is a rich mixture of bacteria, fungi, and microscopic algae, forming a major food source in environments with low primary productivity. The digestive process often involves a highly acidic stomach, sometimes with a pH as low as 1.2, which helps break down cell walls, making the nutrients more accessible.
Predation and Insectivory
While many cichlids are plant-based feeders, a large number are dedicated carnivores, specializing in the consumption of animal prey. Insectivory is a primary diet for countless smaller cichlids, allowing them to thrive on a readily available protein source. These species consume aquatic insect larvae, such as chironomids and mayfly nymphs, which they often forage for in the substrate or among vegetation.
Other insectivores target terrestrial insects that accidentally fall onto the water’s surface, requiring quick strikes and precise feeding mechanics. Larger cichlids often graduate to piscivory, actively hunting and consuming other fish. Piscivores like the Nimbochromis species in Lake Malawi employ various hunting strategies, ranging from patient stalking to aggressive ambush predation.
Nimbochromis fusco is a known ambush predator that lies in wait, concealed by the environment, before quickly darting out to secure its meal. Other species, like Dimidiochromis compressiceps, have laterally compressed, razor-thin bodies that allow them to hide head-down among aquatic plants, making them nearly invisible to juvenile fish they prey upon. The hunting repertoire of some piscivores includes specialized methods, such as the strategy used by Nimbochromis linni to suck small prey out of narrow rock crevices.
Beyond insects and fish, many cichlids consume other invertebrates, including small benthic crustaceans like copepods and shrimp, as well as worms. Molluscivory, or snail-eating, requires a distinct morphological adaptation. Molluscivores possess robust pharyngeal jaws and powerful muscles to crush the hard shells of their prey.
Highly Specialized Feeding Niches
The development of extremely narrow feeding niches has been a major driver of cichlid speciation. One bizarre specialization is lepidophagy, where species feed primarily on the scales and mucus of other fish. The six species of the genus Perissodus in Lake Tanganyika are famous examples of this behavior, with some individuals showing a distinct asymmetry in their mouths.
This mouth asymmetry allows them to attack the flank of a victim from a specific side to efficiently shear off scales with a quick strike. Another highly specific behavior is pedophagy, which involves cichlids that specialize in preying on the eggs and fry of other fish, particularly those that practice mouthbrooding.
These pedophages will often harass a mouthbrooding female until she spits out her clutch, allowing the predator to consume the vulnerable eggs or fry. Morphological adaptations for pedophagy include specialized jaws and heads that can be wedged into the mouths of brooding females to force the release of the offspring.
In a rare adaptation, some species have been noted to target the eyes of other fish. Finally, there are cichlids that feed almost exclusively on plankton and zooplankton, tiny organisms suspended in the water column.
These planktivores, such as certain Haplochromis species, are filter feeders, relying on highly developed gill rakers to efficiently strain small prey from the water as they swim. Gill rakers are bony, comb-like projections on the gill arches that prevent food particles from escaping through the gills. This spectrum of specialized diets illustrates the family’s ability to adapt its feeding apparatus to exploit every available food resource.