Mouthbrooder
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Mouthbrooding, also known as oral incubation and buccal incubation, is the care extended 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, most notably Darwin's frog, fishes are by far the most diverse mouthbrooders. Mouthbrooding has evolved independently in several different families of fish.[1]
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[edit] Families of mouthbrooding fish
Families of fish known to include mouthbrooding species include:
- Apogonidae (cardinalfish): All paternal mouthbrooders
- Ariidae (sea catfish): All paternal mouthbrooders
- Bagridae (Bagrid catfish): One species of biparental mouthbrooders
- Cichlidae (cichlids): Numerous species either paternal, maternal, and biparental mouthbrooders
- Luciocephalidae (pikeheads): All paternal mouthbrooders
- Cyclopteridae (lumpfish): A few species are paternal mouthbrooders
- Opistognathidae (jawfishes): All paternal mouthbrooders
- Osphronemidae (gouramis): A few species are paternal mouthbrooders
- Osteoglossidae (arowanas): All paternal mouthbrooders
[edit] Mouthbrooding behaviour
Paternal mouthbrooders are species where the male looks after the eggs. Paternal mouthbrooders include the arowana, the mouthbrooding betta 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 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 Geophaginae subfamily (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 genera Asprotilapia and Xenotilapia, and a single 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 will be underweight and requiring a period of time to feed and make good 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 parents extent 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.
[edit] Brood parasites
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 will eat the host mouthbrooder's eggs, while spawning and simultaneously laying and fertilizing its own eggs. The mouthbrooder (typically a cichlid) will incubate 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.
[edit] Crocodiles
Mouthbrooding of a sort is also found in crocodiles. Eggs are laid in a nest that the parents guard but otherwise leave alone. However, once the newborn crocodiles start to hatch, they produce high-pitched squeaks that attract the attention of one or both of their parents. The parent will dig up the nest, crack open the eggs with her mouth (displaying a remarkable degree of delicacy for so large an animal), and then transports batches of the hatchlings to the water in her mouth. Typically, as with the Nile crocodile, it is the female that performs these duties, but in some species the male will be involved as well, as is the case with the mugger crocodile.[3]
[edit] References
- ^ Helfman, G., Collette, B, Facey, D.: The Diversity of Fishes, Blackwell Publishing, 1997. ISBN 0-86542-256-7
- ^ Loiselle, P.: The Cichlid Aquarium, Tetra Press, 1985. ISBN 3-923880-20-0
- ^ Alderton, D.: Crocodiles & Aligators of the World, Facts on File, 1985. ISBN 0-8160-2297-6
