Mouthbrooding, also known as oral incubation and buccal incubation, is the care given by some groups of animals to their offspring by holding them in the mouth of the parent for extended periods of time. Although mouthbrooding is performed by a variety of different animals, such as the Darwin's frog, fish are by far the most diverse mouthbrooders. Mouthbrooding has evolved independently in several different families of fish. [1]
Paternal mouthbrooders are species where the male looks after the eggs. Paternal mouthbrooders include the arowana, various mouthbrooding bettas and gouramies such as Betta pugnax , and sea catfish such as Ariopsis felis . Among cichlids, paternal mouthbrooding is relatively rare, but is found among some of the tilapiines, most notably the black-chin tilapia Sarotherodon melanotheron .
In the case of the maternal mouthbrooders, the female takes the eggs. Maternal mouthbrooders are found among both African and South American cichlids. African examples are the haplochromines, such as the mbuna, Astatotilapia burtoni , and the dwarf mouthbrooders Pseudocrenilabrus multicolor, and some of the tilapiines, such as Oreochromis mossambicus and Oreochromis niloticus . The South American maternal mouthbrooders are all members of the subfamily Geophaginae (commonly known as "eartheaters" on account of their substrate-sifting feeding mode) such as Gymnogeophagus balzanii and Geophagus steindachneri .
Biparental mouthbrooding occurs where both parents take some of the eggs. This is relatively rare, but is found among the cichlid genus Xenotilapia , and a single catfish, the spatula-barbled catfish (Phyllonemus typus).
Typically, after courtship, the male fertilises the eggs and then collects them in his mouth, holding onto them until they hatch. During this time he cannot feed. Among the maternal mouthbrooding cichlids, it is quite common (e.g., among the mbuna) for the male to fertilise the eggs only once they are in the female's mouth. Some cichlids are able to feed while mouthbrooding the eggs, but invariably they feed less often than they would otherwise do, and after mouthbrooding one batch of eggs, all mouthbrooding fish are underweight and require a period of time to feed and make up for the depletion of their energy reserves. [2]
In all cases, the eggs are protected until they hatch and the fry become free swimming. Only in some cases does the parent extend protection to mobile juveniles. Among the cichlids and arowanas, extension of brood care to the fry is common, and they have behavioural cues to tell fry swimming and feeding away from the parent that danger is approaching and that they should return to their parent's mouth. By caring for their offspring in this way, mouthbrooding fish are able to produce smaller numbers of offspring with a higher chance of survival than species that offer no broodcare.
Some commercially important fish are mouthbrooders, most notably among the tilapiines and arowanas. Fry harvesting, getting the brooding fish to open its mouth and release the fry, is important if the fry are to be reared artificially. In the case of endangered species, such as Asian arowana, harvesting may be supervised by an official to certify that the fish farm is a genuine producer of captive-bred fish. [3] [4] [5]
Some fish have evolved to exploit the mouthbrooding behaviour of other species. Synodontis multipunctatus , also known as the cuckoo catfish, combines mouthbrooding with the behavior of a brood parasite: it eats the host mouthbrooder's eggs, while spawning and simultaneously laying and fertilizing its own eggs. The mouthbrooder (typically a cichlid) incubates the cuckoo catfish young, the catfish eggs hatch earlier than the cichlid's eggs, and eat the as-yet unhatched cichlid eggs before being set free.
Families of fish known to include mouthbrooding species include:
Cichlids are fish from the family Cichlidae in the order Cichliformes. Cichlids were traditionally 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.
Tilapia is the common name for nearly a hundred species of cichlid fish from the coelotilapine, coptodonine, heterotilapine, oreochromine, pelmatolapiine, and tilapiine tribes, with the economically most important species placed in the Coptodonini and Oreochromini. Tilapia are mainly freshwater fish inhabiting shallow streams, ponds, rivers, and lakes, and less commonly found living in brackish water. Historically, they have been of major importance in artisanal fishing in Africa, and they are of increasing importance in aquaculture and aquaponics. Tilapia can become a problematic invasive species in new warm-water habitats such as Australia, whether deliberately or accidentally introduced, but generally not in temperate climates due to their inability to survive in cold water.
The Wami tilapia is a tilapiine cichlid that grows to over 20 cm in length and is considered a useful food fish in Tanzania and the island of Zanzibar, where it may have been introduced by man. It is tolerant of brackish water and grows well in saline pools, making it particularly suitable for aquaculture by communities living close to the sea. Like other tilapia it is an omnivore and will feed on algae, plants, small invertebrates, and detritus. The common name refers to the Wami River.
Tropheus moorii is a species of cichlid endemic to Lake Tanganyika in Africa. Over 40 different color morphs of this species are dispersed throughout the lake, ranging from dark green to flame red and yellow. They mostly feed on filamentous algae on the rocky shallows they inhabit. T. moorii is a maternal mouthbrooder, so eggs are fertilized and young are carried in the mouth of the female while they hatch and develop.
The Nile tilapia is a species of tilapia, a cichlid fish native to the northern half of Africa and the Levante area, including Israel, and Lebanon. Numerous introduced populations exist outside its natural range. It is also commercially known as mango fish, nilotica, or boulti. The first name leads to easy confusion with another tilapia which is traded commercially, the mango tilapia.
Pseudotropheus crabro, the Bumblebee Cichlid or Hornet Cichlid, is a species of cichlid endemic to Lake Malawi where it is found in different habitats but most frequently in large caves or in the vicinity of large boulders. This species can reach a length of 16 centimetres (6.3 in) SL.
The Tilapiini are a tribe within the family Cichlidae commonly known as tilapiine cichlids. Formerly this tribe contained many other genera and species, including the economically important Oreochromis and Sarotherodon, but a taxonomic review found that this grouping was paraphyletic and most were moved to Coelotilapini, Coptodonini, Heterotilapini, Oreochromini and Pelmatolapiini. Together, most species in these tribes are called "tilapias". In a more distant past, a number of other, more different genera like Steatocranus also were included in Tilapiini. With these as separate, Tilapiini now is a much more restricted tribe with only three genera and about half a dozen species from Central and Southern Africa.
The Mozambique tilapia is an oreochromine cichlid fish native to southeastern Africa. Dull colored, the Mozambique tilapia often lives up to a decade in its native habitats. It is a popular fish for aquaculture. Due to human introductions, it is now found in many tropical and subtropical habitats around the globe, where it can become an invasive species because of its robust nature. These same features make it a good species for aquaculture because it readily adapts to new situations. It is known as black tilapia in Colombia and as blue kurper in South Africa.
Astatotilapia flaviijosephi, the Jordan mouthbrooder, is a vulnerable species of freshwater fish in the family Cichlidae (cichlids). It is found in the central Jordan River system, including Lake Tiberias (Kinneret), in Israel, Jordan and Syria, making it the only haplochromine cichlid to naturally range outside of Africa. This species is too small to be of significant importance to fisheries, unlike the only other cichlids native to the Levant, the economically important tilapias.
The zebra mbuna is a species of cichlid endemic to Lake Malawi in Africa. This species can reach a length of 11.3 cm (4.4 in). It feeds on aufwuchs, a surface layer of mostly algal material that grows on rocks. This cichlid is a mouthbrooder and the female broods the eggs in her mouth for about three weeks. This fish can sometimes be found in the aquarium trade.
Oreochromis lidole is a species of freshwater fish in the family Cichlidae. This tilapia is native to Malawi, Mozambique and Tanzania, where it is found in Lake Malawi, Lake Malombe, the Shire River and perhaps some crater lakes further north. It is important in fisheries, but has drastically declined; it may already be extinct. This oreochromine cichlid is locally called chambo, a name also used for two other closely related species found in the same region, O. karongae and O. squamipinnis.
Oreochromis variabilis, the Victoria tilapia, is a species of African cichlid native to Lake Victoria and its tributaries, Lake Kyoga, Lake Kwania, and Lake Bisina (Salisbury), as well as being found in the Victoria Nile above Murchison Falls. This species can reach a standard length of 30 cm (12 in). This species is important to local commercial fisheries and is potentially important in aquaculture. It is also found in the aquarium trade.
Chromidotilapia guntheri, or Günther's mouthbrooder, is a cichlid from Africa. It was previously considered to consist of two subspecies, the common C. g. guntheri ranges from Liberia to Equatorial Guinea and Niger, and the critically endangered C. g. loennbergi which was thought to be restricted to Lake Barombi-ba-Kotto, a small crater lake in Cameroon but these subspecies are not supported by subsequent authorities. The species is noted for being a biparental mouthbrooder. Eggs are laid on a flat open surface and taken in the parents' mouth. Unlike many mouthbrooding cichlid species, both parents participate in the mouthbrooding.
The hardhead catfish is a species of sea catfish from the northwest Atlantic and Gulf of Mexico, and similar to the gafftopsail catfish. It is one of four species in the genus Ariopsis. The common name, hardhead catfish, is derived from the presence of a hard, bony plate extending rearward toward the dorsal fin from a line between the catfish's eyes. It is an elongated marine catfish that reaches up to 28 in (70 cm) in length and 12 lb (5.5 kg) in weight. Their typical weight is less than 1 lb (450 g), but they commonly reach up to 3 lb (1.4 kg). They are often a dirty gray color on top, with white undersides.
Apistogramma barlowi is a species of dwarf cichlid in the Geophagini tribe of the subfamily Cichlinae, the American cichlids. It is found in forest streams northwest of Pebas town in northern Peru. It was first discovered in Peru in 2000 and scientifically described in 2008. Apistogramma barlowi is a freshwater fish that grows to a length of 6.5 cm (2.6 in). There are two forms which occur in separate parts of its range: a red form that is darker and has red marks on the head, and a white form that is paler. The specific name is in honor of the ichthyologist George W. Barlow.
The mango tilapia is a species of fish from the cichlid family that is native to fresh and brackish waters in Africa and the Levant. Other common names include Galilaea tilapia, Galilean comb, Galilee St. Peter's fish, and St. Peter's fish. This is a relatively large cichlid at up to 41 centimetres (16 in) in total length and about 1.6 kilograms (3.5 lb) in weight. It is very important to local fisheries and the species is also aquacultured.
The blackchin tilapia is a species of cichlid native to coastal west Africa. It is a paternal mouthbrooder which has been introduced to Asia and North America.
Oreochromini is a tribe of cichlids in the Pseudocrenilabrinae subfamily that is native to Africa and Western Asia, but a few species have been widely introduced to other parts of the world. It was formerly considered to be part of the tribe Tilapiini but more recent workers have found that the Tilapiini sensu lato is paraphyletic. Despite this change, species in Oreochromini are still referred to by the common name tilapia and some of the most important tilapia in aquaculture —certain species of Oreochromis and Sarotherodon— are part of this tribe. In contrast, several species have small ranges and are seriously threatened; a few are already extinct or possibly extinct.
Vertebrate maternal behavior is a form of parental care that is specifically given to young animals by their mother in order to ensure the survival of the young. Parental care is a form of altruism, which means that the behaviors involved often require a sacrifice that could put their own survival at risk. This encompasses behaviors that aid in the evolutionary success of the offspring and parental investment, which is a measure of expenditure exerted by the parent in an attempt to provide evolutionary benefits to the offspring. Therefore, it is a measure of the benefits versus costs of engaging in the parental behaviors. Behaviors commonly exhibited by the maternal parent include feeding, either by lactating or gathering food, grooming young, and keeping the young warm. Another important aspect of parental care is whether the care is provided to the offspring by each parent in a relatively equal manner, or whether it is provided predominantly or entirely by one parent. There are several species that exhibit biparental care, where behaviors and/or investment in the offspring is divided equally amongst the parents. This parenting strategy is common in birds. However, even in species who exhibit biparental care, the maternal role is essential since the females are responsible for the incubation and/or delivery of the young.
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