Regurgitation (digestion)

Regurgitation is the expulsion of material from the pharynx, or esophagus, usually characterized by the presence of undigested food or blood.^[1]

Flesh fly, from the family Sarcophagidae "blowing a bubble". One explanation for this behaviour is that it concentrates the fly's meal by the process of evaporation. The diet of the flesh fly is very high in water content. The fly regurgitates the liquid portion of the food, holds it while evaporation reduces the water content and the fly then swallows a much more concentrated meal without the water content. This continues until sufficient amount of liquid is left for the fly. – Australian Museum

Regurgitation is used by a number of species to feed their young.^[2] This is typically in circumstances where the young are at a fixed location and a parent must forage or hunt for food, especially under circumstances where the carriage of small prey would be subject to robbing by other predators or the whole prey is larger than can be carried to a den or nest. Some bird species also occasionally regurgitate pellets of indigestible matter such as bones and feathers.^[3]

It is in most animals a normal and voluntary process unlike the complex vomiting reflex in response to toxins.

Humans

In humans it can be voluntary or involuntary, the latter being due to a small number of disorders. Regurgitation of a person's meals following ingestion is known as rumination syndrome, an uncommon and often misdiagnosed motility disorder that affects eating. It may be a symptom of gastroesophageal reflux disease (GERD).^[4]

In infants, regurgitation – or spitting up – is quite common, with 67% of 4-month-old infants spitting up more than once per day.^[5]

Some people are able to regurgitate without using any external stimulation or drug, by means of muscle control. Practitioners of yoga have also been known to do this.^[6] Professional regurgitators perfect the ability to such a degree as to be able to exploit it as entertainment.^[7][8]

Birds

 

Moorhen chick being fed regurgitated food by an adult

For birds that transport food to their mates and/or their young over long distances — especially seabirds — it is impractical to carry food in their bills because of the risk that it would be stolen by other birds, such as frigatebirds, skuas and gulls. Such birds often employ a regurgitative feeding strategy. Many species of gulls have an orange to red spot near the end of the bill (called a "subterminal spot") that the chicks peck in order to stimulate regurgitation.

All of the Suliformes employ a regurgitative strategy to feed their young. In some species — such as the blue-footed booby, masked booby, and the Nazca booby — a brood hierarchy exists, in which the older chick is fed before the younger, subordinate chick. In times when food is scarce, siblicide may occur, where the dominant chick kills its younger sibling in order to sequester all of the resources of the parents.^[9] Penguins chicks are fed regurgitated food by both parents.^[10][11] Researchers found that the practice may potentially cause metabolic alkalosis in certain penguins.^[12]

Some birds, such as fulmars, employ regurgitation as a defense when threatened.

Other animals

Ruminants regurgitate their food as a normal part of digestion. During their idle time, they chew the regurgitated food (cud) and swallow it again, which increases digestibility by reducing particle size.^{[citation needed]}

Honey is produced by a process of regurgitation by honey bees, which is stored in the beehive as a primary food source.

•  
  Bubbling fly
•  
  Bubbling fly (Calliphora vicina)
• Pollenia sp. blowing bubbles (video, 3m 1s)

See also

• Trophallaxis

References

1. Nelson, R.W. and C. G. Couto. Small Animal Internal Medicine, 4th ed. 2009.
2. Keeling, Linda K.; Gonyou, Harold W. (2001). Social behaviour in farm animals. CABI Publishing. p. 69. ISBN 0-85199-717-1.
3. Loon, Rael; Loon, Hélène (2005). Birds: the inside story. Struik Publishers. p. 183. ISBN 1-77007-151-2.
4. "Rumination Syndrome". Mayo Clinic. Retrieved Jan 26, 2011.
5. Hyman, Paul E.; Milla, Peter J.; Benninga, Marc A.; Davidson, Geoff P.; Fleisher, David F.; Taminiau, Jan (April 2006). "Childhood functional gastrointestinal disorders: neonate/toddler". Gastroenterology. 130 (5): 1519–1526. doi:10.1053/j.gastro.2005.11.065. ISSN 0016-5085. PMID 16678565.
6. Chari, C. T. K. (1973) '"Regurgitation, mediumship and yoga." Journal of the Society for Physical Research 47, 757, 156
7. "Stevie Starr, Professional Regurgitator". The Museum of Hoaxes. Retrieved Jan 26, 2011.
8. Price, Haydn (2007). Chris Needs:Like It Is. Y Lolfa Cyf. p. 112. ISBN 978-1-84771-015-4.
9. Drummond, Hugh; Edda Gonzalez; Jose Luis Osorno (1986). "Parent-Offspring Cooperation in the Blue-footed Booby (Sula nebouxii): Social Roles in Infanticidal Brood Reduction". Behavioral Ecology and Sociobiology. 19 (5): 365–372. doi:10.1007/bf00295710. S2CID 36417383.
10. Ancel, André; Beaulieu, Michaël; Gilbert, Caroline (2013-01-01). "The different breeding strategies of penguins: A review" (PDF). Comptes Rendus Biologies. 336 (1): 1–12. doi:10.1016/j.crvi.2013.02.002. ISSN 1631-0691. PMID 23537764.
11. Janes, Donald N. (1997). "Osmoregulation by Adélie Penguin Chicks on the Antarctic Peninsula". The Auk. 114 (3): 488–495. doi:10.2307/4089249. ISSN 0004-8038. JSTOR 4089249.
12. Sakamoto, Kentaro Q.; Sato, Katsufumi; Kato, Akiko; Fukui, Daisuke; Bando, Gen; Naito, Yasuhiko; Habara, Yoshiaki; Ishizuka, Mayumi; Fujita, Shoichi (2013). "Metabolic alkalosis due to feeding chicks in breeding Adélie penguins Pygoscelis adeliae under natural conditions". Physiological and Biochemical Zoology. 83 (2): 232–238. doi:10.1086/597517. hdl:2115/48302. ISSN 1537-5293. PMID 19302032. S2CID 18496199.