Other cichlids are detritivores and eat organic material, called Aufwuchs; among these species are the tilapiines of the genera Oreochromis, Sarotherodon, and Tilapia.
Other cichlids are predatory and eat little or no plant matter. These include generalists that catch a variety of small animals, including other fishes and insect larvae (e.g. Pterophyllum), as well as variety of specialists. Trematocranus is a specialized snail-eater, while Pungu maclareni feeds on sponges. A number of cichlids feed on other fish, either entirely or in part. Crenicichla species are stealth-predators that lunge from concealment at passing small fish, while Rhamphochromis species are open-water pursuit predators that chase down their prey. Paedophagous cichlids such as the Caprichromis species eat other species' eggs or young, in some cases ramming the heads of mouthbrooding species to force them to disgorge their young. Among the more unusual feeding strategies are those of Corematodus, Docimodus evelynae, Plecodus, Perissodus, and Genyochromis spp., which feed on scales and fins of other fishes, a behavior known as lepidophagy, along with the death-mimicking behaviour of Nimbochromis and Parachromis species, which lay motionless, luring small fish to their side prior to ambush.
This variety of feeding styles has helped cichlids to inhabit similarly varied habitats. Its pharyngeal teeth (teeth in the throat) afford cichlids so many "niche" feeding strategies, because the jaws pick and hold food, while the pharyngeal teeth crush the prey.
Aggressive behavior in cichlids is ritualized and consists of multiple displays used to seek confrontation while being involved in evaluation of competitors, coinciding with temporal proximity to mating. Displays of ritualized aggression in cichlids include a remarkably rapid change in coloration, during which a successfully dominant territorial male assumes a more vivid and brighter coloration while a subordinate or "non-territorial" male assumes a dull-pale coloration. In addition to color displays, cichlids employ their lateral lines to sense movements of water around their opponents to evaluate the competing male for physical traits/fitness. Male cichlids are very territorial due to the pressure of reproduction, males establish their territory and social status by physically driving out challenging males (novel intruders) through lateral displays (parallel orientation, uncovering gills), biting, or mouth fights (head-on collisions of ajar mouths, measuring jaw sizes, and biting each other's jaws). The cichlid social dichotomy is composed of a single dominant with multiple subordinates, where the physical aggression of males become a contest for resources (mates, territory, food). Female cichlids prefer to mate with a successfully alpha male with vivid coloration, whose territory has food readily available.
Cichlids mate either monogamously or polygamously. The mating s
Cichlids mate either monogamously or polygamously. The mating system of a given cichlid species is not consistently associated with its brooding system. For example, although most monogamous cichlids are not mouthbrooders, Chromidotilapia, Gymnogeophagus, Spathodus and Tanganicodus all include – or consist entirely of – monogamous mouthbrooders. In contrast, numerous open- or cave-spawning cichlids are polygamous; examples include many Apistogramma, Lamprologus, Nannacara, and Pelvicachromis species.
Most adult male cichlids, specifically in the cichlid tribe Haplochromini, exhibit a unique pattern of oval-shaped, color dots on their anal fins. These phenomena are known as egg-spots and aid in the mouthbrooding mechanisms of cichlids. The egg-spots consist of carotenoid-based pigment
Most adult male cichlids, specifically in the cichlid tribe Haplochromini, exhibit a unique pattern of oval-shaped, color dots on their anal fins. These phenomena are known as egg-spots and aid in the mouthbrooding mechanisms of cichlids. The egg-spots consist of carotenoid-based pigment cells, which indicates a high cost to the organism, when considering that fish are not able to synthesize their own carotenoids.
The mimicry of egg-spots is used by males for the fertilization process. Mouthbrooding females lay eggs and immediately snatch them up with their mouths. Over millions of years, male cichlids have evolved egg-spots to initiate the fertilization process more efficiently. When the females are snatching up the eggs into their mouth, the males gyrate their anal fins, which illuminates the egg-spots on his tail. Afterwards, the female, believing these are her eggs, places her mouth to the anal fin (specifically the genital papilla) of the male, which is when he discharges sperm into her mouth and fertilizes the eggs.
The genuine color of egg spots is a yellow, red or orange inner circle with a colorless ring surrounding the shape. Through phylogenetic analysis, using the mitochondrial ND2 gene, it was hypothesized that the true egg spots evolved in the common ancestor of the Astatoreochromis-lineage and the modern Haplochrominis. This ancestor was most likely riverine in origin, based on the most parsimonious representation of habitat type in the cichlid family. The presence of egg-spots in a turbid riverine environment, would seem particularly beneficial and necessary for intra-species communication.
There are two pigmentation genes that are found to be associated with egg-spot patterning and color arrangement. These are fhl2-a and fhl2-b, which are paralogs. These genes aid in pattern formation and cell-fate determination in early embryonic development. The highest expression of these genes was temporally correlated with egg-spot formation. A SINE (short interspersed repetitive element) was also seen to be associated with egg-spots. Specifically, it was evident upstream of the transcriptional start site of fhl2 in only haplochrominis species with egg-spots
Pit-spawning, also referred to as substrate breeding, is a behavior in cichlid fish in which a fish will build a pit in the sand or ground where they will court their mate and consequently spawn with them. There are many different factors that go into this behavior of pit-spawning including female choice of the male and pit size, as well as the male defense of the pits once they are dug in the sand. Cichlids are often divided into two main groups: mouthbrooders and substrate brooders. There are different parenting investment levels and behaviors associated with each type of reproduction. As pit-spawning is a reproductive behavior, there are many different physiological changes that occur in the cichlid while this process is occurring that interferes with social interaction. There are different kinds of species that pit-spawn and many different morphological changes that occur because of this behavioral experience that has been studied in cichlids. Pit-spawning is an evolved behavior across the cichlid group. There is phylogenetic evidence from cichlids in Lake Tanganyika that could be helpful in uncovering the evolution of their reproductive behaviors. There are several important behaviors that are associated with pit-spawning, including parental care, food provisioning, and brood guarding.
Mouthbrooders vs. pit-spawning
One of the differences studied in African cichlids is the difference in their reproductive behavior. There are some species who pit-spawn and some who are known as mouthbrooders. Mouthbrooding is a reproduction technique where the fish will scoop up eggs and fry for protection.One of the differences studied in African cichlids is the difference in their reproductive behavior. There are some species who pit-spawn and some who are known as mouthbrooders. Mouthbrooding is a reproduction technique where the fish will scoop up eggs and fry for protection. While this reproductive behavior differs from species to species in the details, the general basis of the behavior is the same. This differs completely from the other reproductive behavior of cichlids, pit-spawning. As stated in the introduction, pit-spawning is when cichlids dig pits for their eggs rather than holding them in their mouths. These two types of behavior differ not only in the way that they care for their eggs and fry but also how they choose their mates and breeding grounds. In a 1995 study, Nelson found that in pit-spawning females will choose with which males to mate based on the size of the pit that they dig as well as some of the physical characteristics shown in the males. Pit-spawning also differs from mouthbrooding in the size and post-natal care that is exhibited. Eggs that have been hatched from pit-spawning cichlids are usually smaller than those of mouthbrooders. Pit-spawners' eggs are usually around 2 mm while mouthbrooders are typically around 7 mm. While there are different behaviors that take place -post-natally between mouthbrooders and pit-spawners, there are some similarities. Something that both mouthbrooders and pit-spawning cichlids have in common is that the female in both cases will take care of their young after they are hatched. In some cases, there is biparental care, discussed in a later section, but the female will always take an interest in caring for the eggs and newly hatched fry.
How pit-spawning is done
There are many
There are many different species of cichlid that use pit-spawning as reproductive behavior, but one of the less commonly studied species that exhibit this behavior is the Neotropical cichlid fish or the Cichlasoma dimerus. This fish is a substrate-breeder who displays biparental care after the fish have hatched from their eggs. In a study done by Alonso, et al., they studied the reproductive behavior as well as the social behavior of this particular species to see how they accomplished their pit-spawning as well as behaviors associated with the social aspect of these animals. These researchers looked at a variety of different physiological factors in the cichlids including hormone levels, color changes, plasma cortisol levels, as well as their behavior directly associated with pit-spawning. They found that the entire spawning process could take about ninety minutes and anywhere between 400 and 800 eggs could be laid in the process. The female would deposit ~ten eggs at a time, attaching them to the spawning surface which may be a pit constructed on the substrate or another surface. They found that the number of eggs that were laid correlated to the amount of space that they had on the substrate. Once the eggs were attached, the male would swim over the eggs and fertilize them. The parents would then dig pits in the sand, 10–20 cm wide and 5–10 cm deep where larvae would be transferred after hatching. Larvae would begin swimming eight days after fertilization and parenting behaviors, as well as some of the physiological factors measured, would change.
In Alonso's study, they noted
In Alonso's study, they noted that color changes were present before and after the pit-spawning occurred. For example, after the larvae were transferred and the pits were beginning to be protected, their fins turned a dark grey color. In another study, done by Brown and Marshall, they studied the Rainbow Cichlid, Herotilapia multispinosa. In this study, they looked at the color change that occurs in this fish throughout the spawning process. They found that pre-spawning, the Rainbow Cichlid was an olive color with grey bands. Once pre-spawning behaviors started, the body and fins of the fish became more of a gold color. When the eggs are finished being laid, the pelvic fin all the way back to the caudal fin turns to a darker color and blackens in both the males and the females.
As mentioned previously, a study done by Nelson shows that females prefer a bigger pit size when choosing where to lay eggs. Another study done by York, et al., shows that there are differences in the sizes of pits that pit-spawning cichlids create, as well as a change in the morphology of the pits. They found that there may be evolutionary differences between species of fish that cause them to either create pits or castles when spawning. The differences that they found were changes in the way that each species fed, their macrohabitat, and the ability of their sensory systems.
Cichlids are renowned for their recent, rapid evolutionary radiation, both across the entire clade and within different communities across separate habitats. Within their phylogeny, there have been many parallel instances of lineages evolving to the same trait and multiple cases of reversion to an ancestral trait. The family Cichlidae arose between 80 and 100 million years ago within the order Perciformes (perch-like fishes). Cichlidae can be split into a few groups based on their geographic location: Madagascar, Indian, African, and Neotropical (or South American). The most famous and diverse group, the African cichlids, can be further split either into Eastern and Western varieties, or into groups depending on which lake the species is from: Lake Malawi, Lake Victoria, or Lake Tanganyika. Of these subgroups, the Madagascar and Indian cichlids are the most basal and least diverse. Of the African cichlids, the West African or Lake Tanganyika cichlids are the most basal.
Cichlids' common ancestor is believed to have been a spit-spawning species. Both Madagascar and Indian cichlids retain this feature. However, of the African cichlids, all extant substrate brooding species originate solely from Lake Tanganyika. The ancestor of the Lake Malawi and Lake Victoria cichlids were mouthbrooders. Similarly, only around 30% of South American cichlids are thought to retain the ancestral substrate-brooding trait. Mouthbrooding is thought to have evolved individually up to 14 times, and a return to substrate brooding as many as 3 separate times between both African and Neotropical species.
Cichlids can have materna
Cichlids can have maternal, paternal, or biparental care. Maternal care is most common among mouth-brooders, however cichlids' common ancestor is thought to exhibit paternal-only care. Other individuals outside of the parents may also play a role in raising young; in the biparental daffodil cichlid (Neolamprologus pulcher), closely related satellite males, those males who surround other males territories and attempt to mate with female cichlids in the area, help rear the primary male's offspring as well as their own.
A common form of brood care involves food provisioning. For example, female Lyretail cichlids (Neolamprologus modabu) will dig at sandy substrate more to push nutritional detritus and zooplankton into the surrounding water. Adult N. modabu perform this strategy to collect food for themselves, however will dig more when offspring are present, likely to feed their fry. This substrate-disruption strategy is rather common and can also be seen in Convict cichlids (Cichlasoma nigrofasciatum). Other cichlids have an ectothermal mucous that they grow and feed to their young, while still others chew and distribute caught food to offspring. These strategies, however, are less common in pit-spawning cichlids.
Cichlids have highly organized breeding activities. All species show some form of parental care for both eggs
, often nurturing free-swimming young until they are weeks or months old.
Communal parental care, where multiple monogamous pairs care for a mixed school of young have also been observed in multiple cichlid species, including Amphilophus citrinellus
, Etroplus suratensis
, and Tilapia rendalli
Comparably, the fry of Neolamprologus brichardi
, a species that commonly lives in large groups, are protected not only by the adults, but also by older juveniles
from previous spawns.
Several cichlids, including discus (Symphysodon
spp.), some Amphilophus
, and Uaru
species, feed their young with a skin secretion
from mucous glands.
The species Neolamprologus pulcher uses a cooperative breeding system, in which one breeding pair has many helpers which are subordinate to the dominant breeders.
Parental care falls into one of four categories: substrate or open brooders, secretive cave brooders (also known as guarding speleophils), and at least two types of mouthbrooders, ovophile mouthbrooders and larvophile mouthbrooders.
Open broodingNeolamprologus pulcher uses a cooperative breeding system, in which one breeding pair has many helpers which are subordinate to the dominant breeders.
Parental care falls into one of four categories: substrate or open brooders, secretive cave brooders (also known as guarding speleophils), and at least two types of mouthbrooders, ovophile mouthbrooders and larvophile mouthbrooders.
Open- or substrate-brooding cichlids lay their eggs in the open, on rocks, leaves, or logs. Examples of open-brooding cichlids include Pterophyllum and Symphysodon species and Anomalochromis thomasi. Male and female parents usually engage in differing brooding roles. Most commonly, the male patrols the pair's territory and repels intruders, while the female fans water over the eggs, removing the infertile and leading the fry while foraging. However, both sexes are able to perform the full range of parenting behaviours.
Secretive cave-spawning cichlids lay their eggs in caves, crevices, holes, or discarded mollusc shells, frequently attaching the eggs to the roof of the chamber. Examples include Pelvicachromis spp., Archocentrus spp., and Apistogramma spp. Free-swimming fry and parents communicate in captivity and in the wild. Frequently, this communication is based on body movements, such as shaking and pelvic fin flicking. In addition, open- and cave-brooding parents assist in finding food resources for their fry. Multiple neotropical cichlid species perform leaf-turning and fin-digging behaviors.
Ovophile mouthbrooders incubate their eggs in their mouths as soon as they are laid, and frequently mouthbrood free-swimming fry for several weeks. Examples include many East African Rift lakes (Lake Malawi, Lake Tanganyika and Lake Victoria) endemics, e.g.: Maylandia, Pseudotropheus, Tropheus, and Astatotilapia burtoni, along with some South American cichlids such as East African Rift lakes (Lake Malawi, Lake Tanganyika and Lake Victoria) endemics, e.g.: Maylandia, Pseudotropheus, Tropheus, and Astatotilapia burtoni, along with some South American cichlids such as Geophagus steindachneri.
Larvophile mouthbrooders lay eggs in the open or in a cave and take the hatched larvae into the mouth. Examples include some variants of Geophagus altifrons, and some Aequidens, Gymnogeophagus, and Satanoperca, as well as Oreochromis mossambicus and Oreochromis niloticus. Mouthbrooders, whether of eggs or larvae, are predominantly females. Exceptions that also involve the males include eretmodine cichlids (genera Spathodus, Eretmodus, and Tanganicodus), some Sarotherodon species (such as Sarotherodon melanotheron), Chromidotilapia guentheri, and some Aequidens species. This method appears to have evolved independently in several groups of African cichlids.
pharyngeal jaw apparatus. These different jaw apparatus allow for a broad range of feeding strategies including: algae scraping, snail crushing, planktivores, piscivores, and insectivores.
Some cichlids can also show phenotypic plasticity
in their pharyngeal jaws, which can also help lead to speciation. In response to different diets or food scarcity, members of the same species can display different jaw morphologies that are better suited to different feeding strategies. As species members begin to concentrate around different food sources and continue their life cycle, they most likely spawn with like individuals. This can reinforce the jaw morphology and given enough time, create new species.
Such a process can happen through allopatric speciation
, whereby species diverge according to different selection pressures in different geographical areas, or through sympatric speciation
, by which new species evolve from a common ancestor while remaining in the same area. In Lake Apoyo
, Amphilophus zaliosus
and its sister species Amphilophus citrinellus
display many of the criteria needed for sympatric speciation.
In the African rift lake system
, cichlid species in numerous distinct lakes evolved from a shared hybrid swarm
In 2010, the International Union for Conservation of Nature classified 184 species as vulnerable, 52 as endangered, and 106 as critically endangered. At present, the IUCN only lists Yssichromis sp. nov. "argens" as extinct in the wild, and six species are listed as entirely extinct, but it is acknowledged that many more possibly belong in these categories (for example, International Union for Conservation of Nature classified 184 species as vulnerable, 52 as endangered, and 106 as critically endangered. At present, the IUCN only lists Yssichromis sp. nov. "argens" as extinct in the wild, and six species are listed as entirely extinct, but it is acknowledged that many more possibly belong in these categories (for example, Haplochromis aelocephalus, H. apogonoides, H. dentex, H. dichrourus and numerous other members of the genus Haplochromis have not been seen since the 1980s, but are maintained as Critically Endangered in the small chance that tiny –but currently unknown– populations survive).
Nile perch (Lates niloticus
), Nile tilapia
), and water hyacinth
that led to water siltation
, and overfishing
, many Lake Victoria
cichlid species have become extinct or been drastically reduced. By around 1980, lake fisheries yielded only 1% cichlids, a drastic decline from 80% in earlier years.
By far the largest Lake Victoria group are the haplochromine cichlids, with more than 500 species, but at least 200 of these (approximately 40%) have become extinct, and many others are seriously threatened. Initially it was feared that the percentage of extinct species was even higher, but some species have been rediscovered after the Nile perch started to decline in the 1990s. Some species have survived in nearby small satellite lakes, or in refugia among rocks or papyrus sedges (protecting them from the Nile perch), and many others are seriously threatened. Initially it was feared that the percentage of extinct species was even higher, but some species have been rediscovered after the Nile perch started to decline in the 1990s. Some species have survived in nearby small satellite lakes, or in refugia among rocks or papyrus sedges (protecting them from the Nile perch), or have adapted to the human-induced changes in the lake itself. The species were often specialists and these were not affected to the same extent. For example, the piscivorous haplochromines were particularly hard hit with a high number of extinctions, while the zooplanktivorous haplochromines reached densities in 2001 that were similar to before the drastic decline, although consisting of fewer species and with some changes in their ecology.
Although cichlids are mostly small- to medium-sized, many are notable as food and game fishes. With few thick rib bones and tasty flesh, artisan fishing is not uncommon in Central America and South America, as well as areas surrounding the African rift lakes.
The most important food cichli
The most important food cichlids, however, are the tilapiines of North Africa. Fast growing, tolerant of stocking density, and adaptable, tilapiine species have been introduced and farmed extensively in many parts of Asia and are increasingly common aquaculture targets elsewhere.
Farmed tilapia production is about 1,500,000 t (1,500,000 long tons; 1,700,000 short tons) annually, with an estimated value of US$1.8 billion, about equal to that of  about equal to that of salmon and trout.
Unlike those carnivorous fish, tilapia can feed on algae or any plant-based food. This reduces the cost of tilapia farming, reduces fishing pressure on prey species, avoids concentrating toxins that accumulate at higher levels of the food chain, and makes tilapia the preferred "aquatic chickens" of the trade.
Many large cichlids are popular game fish. The peacock bass (Cichla species) of South America is one of the most popular sportfish. It was introduced in many waters around the world. In Florida, this fish generates millions of hours of fishing and sportfishing revenue of more than US$8 million a year. Other cichlids preferred by anglers include the oscar, Mayan cichlid (Cichlasoma urophthalmus), and jaguar guapote (Parachromis managuensis).