The earliest known cichlid fossils were collected in South America, dating back to the Eocene (57 to 37 million years ago), and in Africa, dating back to the Oligocene (33.7 to 23.8 million years ago). However, the fossil history is poor and it is widely believed that the cichlids, along with other labroid families, arose sometime early in the Cretaceous epoch (144 to 66.4 million years ago). Despite the paucity of fossils, investigators have identified several existing Malagasy and Asian genera as the least derived within the Cichlidae. Researchers have gained a good understanding of the evolutionary biology of cichlids from this discovery. For instance, substrate brooding is considered the ancestral breeding system because it is practiced by the oldest genera in Madagascar and Asia.
Cichlids follow a typical developmental pattern but some species brood the eggs in the mouth while developing. Parents exhibit various behaviors to promote the growth of young, which develop through three distinct stages: eggs, wrigglers (newly hatched, non-free-swimming young), and fry (free swimming but dependent on the parent). At the early stages of development, parents fan the eggs to provide ventilation and remove waste (termed “fanning”). Some species use their mouths to suck away wastes or to remove dead or fungus-ridden eggs (termed “mouthing”). Mouthbrooding species that carry developing eggs in the buccal cavity (mouth) accomplish mouthing and fanning by rolling and swishing the eggs in the mouth (termed “churning”). Finally, several behaviors are related to aiding the young in feeding. Parents may pick up leaf matter and drop it near the young so they may forage on the unexposed side (termed “leaf-lifting”), or dig into the substrate with the fins to expose buried prey (termed “findigging”). Another unusual method of aiding the fry in development is “micronipping,” in which fry feed on mucous secreted from the skin of parents. Micronipping was first discovered in Symphysodon discus, but has since been recorded for several other cichlid species.
Some species of blue tilapia (among others), which are widely used in aquaculture, are susceptible to sex change for a period approximately 30-40 days after hatching by controlling temperature or adding hormones (See Mating Systems). Despite the fact that genetics also influence sex determination, hormones and temperature can overrule genetic determination, creating offspring that are all one sex. Aquaculturists take advantage of this fact to create single sex tanks, thus avoiding overpopulation.
Development - Life Cycle: temperature sex determination
Keenleyside, M. 1991. Parental Care. Pp. 191-208 in M Keenleyside, ed. Cichlid Fishes: Behavior, Ecology and Evolution. London: Chapman and Hall.
The lifespan of many wild cichlids is unknown. However, in aquaria they are relatively long-lived, about 10 years on average. Several can reach up to 18 years in captivity, suggesting that at least some cichlids have considerably long lifespans.
The diversity of habitats occupied by cichlids is matched by the number of mating systems they employ. In fact, the local ecological conditions are an important indicator of the mating system used, which may vary within the same species. The most primitive condition is monogamy, with males and females essentially monomorphic, excepting some coloring details. Courtship rituals and parental care are common among monogamous pairs. Some cichlids are polygynous: males fertilize the eggs of more than one female. In this system, males might defend a territory that females visit to spawn (only once during the season), two females may defend a territory overlapping that of a male (bigamy), or a male may dominate a harem of multiple females. Cichlids also employ polyandry, in which females mate with several males. In one extraordinary case, sex roles are essentially reversed. Sarotherodon melanotheron males nurture eggs and fry in the mouth for 15 days after spawning, while females are capable of spawning just a week later. This creates a situation where the availability of males to brood the eggs is the limiting factor in reproduction. Behavioral studies reveal that male Sarotherodon melanotheron are less aggressive, and more selective, choosing larger females. Next, some cichlids may be promiscuous (polygynandrous).
An intriguing form of promiscuous spawning in some planktivorous cichlids (and at least one non-planktivorous cichlid as well) is termed “lekking,” a Swedish word meaning “to play.” Amazingly, from 5,000 to 50,000 males may congregate during lekking, which occurs over a long breeding season in some cichlids. Some lekking species, such as Copadichromis eucinostomous, migrate inshore and build volcano-like nests out of sand , while others lek in open waters, such as Paracyprichromis brieni. Females then mate with between 4 and 12 males, distributing a few eggs to each. A final mating system, termed “extended family” is found in at least one cichlid species, Neolamprologus multifasciatus. In this scenario, there are colonies of approximately 19 individuals (one to three males, up to five females, and the rest juveniles) with a large dominant male (alpha) and one other male (beta) participating in spawning. A number of individuals in each colony are related (outsiders may occasionally join a colony) and there are overlapping generations within each colony.
In Lake Tanganyika, Neolamprologus tetracanthus illustrates the utility of multiple mating systems in a dynamic environment. In one habitat, where the bottom is barren and predators are abundant, Neolamprologus tetracanthus males remain with their spawning partner to guard the fry. In a different part of the lake, predators are less abundant and populations are larger. There, numerous females establish individual feeding areas and male territories encompass as many as 14 females. The males spawn with each female and exhibit no parental care – an extreme case of polygyny. Numerous other studies support the existence of “plastic” mating strategies among cichlids. St. Peters fishes, of northern Africa, Israel and Jordan, illustrate how distinctions between mating systems are blurred by a single pair of spawning cichlids. Pairs form after a prolonged courtship ritual. After the eggs are fertilized, they may be taken by the male, female, or both as they go their separate ways. The parent that doesn’t take the eggs is free to spawn again. Finally, in harem-forming species and lekking mouth-brooders, smaller or weaker males may attempt to covertly fertilize a female—variously called sneaking, cheating, or parasitic spawning. During lekking males may accomplish this by mimicking females. Parasitic spawning is rare among monogamous species, probably because males and females remain in close proximity while spawning.
There are two general modes of cichlid reproduction: substrate brooding and mouthbrooding. Substrate brooding (or nest building) represents the initial (evolutionarily) reproductive strategy, evidenced by the fact that the most primitive species are substrate brooders (See Other Comments). Substrate brooders tend to be monogamous and sexually monomorphic. The egg sacs usually adhere to hard surfaces and the helpless larvae (termed wrigglers), which have large yolk sacs, remain guarded in the nest until they can swim (and are then termed fry). The nests of substrate brooders range from sand castles to sand craters to accumulations of snail shells. Most mouthbrooders are polygynous and sexually dimorphic , although several species are monogamous. The eggs and wrigglers are carried in the mouth of the female , or in monogamous species, both males and females carry larvae in their mouths. As one might expect with such a diverse group of fishes, there is wide variation between the two general patterns described above (See Reproduction: Mating Systems). Many cichlids mate year round and the number of eggs ranges from just a few to several hundred across the family.
Parental care is likely the most intriguing life history feature of cichlids. Cichlids are well known for their strategy of mouthbrooding, in which the eggs, wrigglers (newly hatched, non-free-swimming young), or fry are carried in the mouth of an individual. In some mouthbrooding species there is no contact with the substrate; the unfertilized eggs are carried in the mouth of the male or female (termed immediate or ovophilic parental care). In others, the eggs are adhered to a substrate, fertilized and taken into the parents mouth after hatching (termed delayed or larvophilic parental care). Female (maternal) mouthbrooding is most common and well known but in at least one species, Sarotherodon melanotheron, the male carries the young (paternal mouthbrooding). In several other species mouthbrooding is biparental, shared by the male and female. Substrate brooders also guard their young, usually in some cooperative parenting system, such as biparental monogamy. Substrate brooding species also expend considerable energy caring for young. The eggs are initially attached to a substrate where they are cared for intensively. The newly hatched wrigglers may be transferred to a newly excavated pit, a patch of leaves, or the rootlets of aquatic vegetation where they are suspended by threads of mucous. The fry move along the substrate feeding on small particles while the parents keep guard.
In both substrate and mouthbrooding species parents use physical movements (termed “calling behaviors”), such as flicking the pelvic fins or jogging the head, when predators approach. These movements serve as cues for fry to retreat, either settling to the substrate near the parent or entering the mouth depending on the type of parental care. Experiments have shown that the level of vulnerability of young is the main determinant of continued parental care, rather than a set time period after hatching. Several other behaviors relating to parental care are described in Development.
Parental Investment: male parental care ; female parental care
Barlow, G. 2000. The Cichlid Fishes: Nature's Grand Experiment in Evolution. Cambridge, MA: Perseus Publications.
Barlow, G. 1991. Mating Systems among Cichlid Fishes. Pp. 173-190 in M Keenleyside, ed. Cichlid Fishes: Behavior, Ecology and Evolution. London: Chapman and Hall.
Keenleyside, M. 1991. Parental Care. Pp. 191-208 in M Keenleyside, ed. Cichlid Fishes: Behavior, Ecology and Evolution. London: Chapman and Hall.
Barcode of Life Data Systems (BOLD) Stats Specimen Records:4818 Specimens with Sequences:4334 Specimens with Barcodes:3919 Species:456 Species With Barcodes:425 Public Records:1787 Public Species:259 Public BINs:211
The Cichlidae family stands out as an extraordinary example of vertebrate evolution. From the sheer size of the family to the complexity of their ecological interactions and rapid evolution, cichlids provide a unique glimpse of the many factors that promote speciation. The behavioral and physical changes resulting from intense speciation in cichlids is equally impressive. Cichlids demonstrate some of the most unique and intensive parenting in fishes and utilize several different mating systems, from monogamy to polygynandry (See Reproduction). Many feeding behaviors found in cichlids are unique among freshwater fishes (See Behavior and Food Habits). Finally, although the general body plan of cichlids is constant, they come in a dazzling array of shapes, sizes, colors, and dental plans, making them popular with aquarists and aquaculturists (See Physical Description and Economic Importance to Humans).
There are no concrete figures on the number of genera and species in the Cichlidae family because there are still many revisions being made and a considerable number of species are yet to be described. Rough estimates range from 200 to 2000 species and approximately 140 genera, which, after Cyprinidae and Gobiidae, would make them the third largest family of bony fishes. The largest genus is the African Crenicichla with over 100 species. Cichlids inhabit fresh waters, and many species are endemic to isolated lake environments. The fact that no genera occur on more than one continent illustrates the degree of endemism in this family.
Berra, T. 2001. Freshwater Fish Distribution. San Diego, CA: Academic Press.
Nelson, J. 1994. Fishes of the World – third edition. New York, NY: John Wiley and Sons.
Moyle, P., J. Cech. 2000. Fishes: An introduction to ichthyology – fourth edition. Upper Saddle River, NJ: Prentice-Hall.
Wheeler, A. 1985. The World Encyclopedia of Fishes - second edition. London: Macdonald.
Greenwood, P., M. Stiassny. 2002. Cichlids. Pp. 200-204 in W Eschmeyer, J Paxton, eds. Encyclopedia of fishes – second edition. San Diego, CA: Academic Press.
Stiassny, M. 1991. Phylogenic Intrarelationships of the Family Cichlidae: An Overview. Pp. 1-35 in M Keenleyside, ed. Cichlid Fishes: Behavior, Ecology and Evolution. London: Chapman and Hall.
Because many cichlid species are endemic to small geographic areas, they can be threatened relatively easily. Many cichlid species will never be described because they are going extinct so quickly. Such is the case with cichlids of Lake Victoria after the introduction of Nile perch. Nile perch were introduced as a food source (unsupervised) but, as a voracious predator, began to destroy cichlid populations throughout the lake. This has resulted in the largest mass extinction of endemic species in recent times. Conservative estimates are that across the Cichlidae family, 43 cichlids are extinct, five are extinct in the wild, 37 species are critically endangered, 11 species are endangered, 34 species are vulnerable, and one species is at low risk.
The World Conservation Union, 2002. "IUCN 2002" (On-line). IUCN Red List of Threatened Species. Accessed September 27, 2003 at http://www.iucnredlist.org/.
Cichlids are mainly found in the lowland, freshwater areas of tropical and subtropical regions. However, some of the most primitive species, which are found in Madagascar (17 species) and Asia, also inhabit brackish waters. Some other areas with brackish-water species include coastal India and Sri Lanka (three species), and Cuba and Hispaniola (four species). The great majority of cichlids are found in the Great Lakes of East Africa (Lake Malawi, Lake Victoria, and Lake Tanganyika), where between 800 and 2100 species are thought to exist. Nearly all of these species are endemic (evolved in and confined to a particular place) to the lake they inhabit. There are approximately 150 river species in the region as well. The remaining distribution includes South America (approximately 290 species), Central America and Mexico (approximately 95 species), North America (one species), and the Middle East - Iran, Syria, Israel and Palestine (five species).
Cichlids have been widely introduced, either deliberately for aquaculture or accidentally through the aquarium trade (Lever, 1996). For instance, in the United States there is only one native species, the Rio Grande cichlid, but 44 species have been introduced. Florida has proven ideal for many exotic cichlids like the oscar, peacock cichlid, and Jack Dempsey, due to its warm climate and abundant water.