View source for Biology:Dewlap

{{Short description|Skin hanging below the jaw of animals}}
[[File:Mastif angielski pregowany 768.jpg|thumb|right|A mastiff with a dewlap, seen connecting from the neck to the lower jaw.]]
A  '''dewlap''' is a longitudinal flap of [[Biology:Skin|skin]] or similar flesh that hangs beneath the lower jaw or [[Medicine:Neck|neck]] of many [[Biology:Vertebrate|vertebrate]]s. More loosely, it can be various similar structures in the neck area, such as those caused by a double chin or the submandibular [[Biology:Vocal sac|vocal sac]] of a [[Biology:Frog|frog]]. More generally, it can be any hanging mass of skin, such as a fold of loose skin on an elderly [[Biology:Human|person]]'s neck, or the [[Biology:Wattle (anatomy)|wattle]] of a [[Biology:Bird|bird]].  Dewlaps can be considered as a [[Biology:Caruncle (bird anatomy)|''caruncle'']], defined as "a small, fleshy [[Biology:Tubercle|excrescence]] that is a normal part of an animal's anatomy".<ref>{{cite web|url=http://www.lexic.us/definition-of/caruncle|title=Definition of caruncle|author=Lexic.us|access-date=April 20, 2013}}</ref>

==Etymology==
The word is first attested in the mid 1300s as ''dewelappe'' ("fold of skin that hangs from the throat of oxen and kine"), from ''lappe'' ("loose piece", from [[Social:Old English|Old English]] {{wiktang|læppa}}), but the first element ''*dew(e)-'' is of nebulous origin and meaning; it probably was altered by [[Social:Folk etymology|folk etymology]] with "dew". Old English had ''fræt-læppa'' in the aforementioned sense (and [[Social:Middle English|Middle English]] ''fresh-lappe''). There also seems to be a cognate to Danish dialectal {{wiktda|doglæp}} ("flap of skin that sweeps dew from grass, especially on the neck of an ox"),<ref>{{Cite web |title=doglæp — Den Danske Ordbog |url=https://ordnet.dk/ddo/ordbog?query=dogl%C3%A6p |access-date=2022-03-25 |website=ordnet.dk}}</ref> but this might be a parallel independent development.

From the 1580s onward, it was applied to the fleshy fold or [[Biology:Wattle (anatomy)|wattle]] of a [[Biology:Turkey (bird)|turkey]] and also to a flaccid, elderly human throat.<ref>{{Cite web|last=Harper|first=Douglas R.|title=dewlap (n.)|url=https://www.etymonline.com/word/dewlap#etymonline_v_8497|website=Online Etymological Dictionary}}</ref>

==Mammals==
[[File:Bos taurus indicus.jpg|thumb|right|A zebu with a large dewlap.]]
Many mammals such as dogs, [[Biology:Rabbit|rabbit]]s and moose possess dewlaps. In [[Biology:Zebu|zebu]] cattle, the dewlap is colloquially known as the "briefcase folds".{{citation needed|date=November 2016}} The dewlap is also seen in both sexes of moose.

===Rabbits===
[[File:Palomino rabbit with kit.jpg|thumb|A palomino rabbit displaying her dewlap beside a month-old kit]]
In rabbits, the dewlap is a secondary sex characteristic of [[Biology:Female|female]] rabbits which grows once the doe reaches sexual maturity. In laboratory conditions, when a butyl alcohol extract of the urine of [[Medicine:Pregnancy|pregnant]] women was administered to male rabbits, they developed a dewlap, which then gradually disappeared once the administration ceased. If a female rabbit is ovarectomized before reaching maturity, the dewlap never develops, and even when an ovarectomy is performed on a mature female rabbit with a dewlap, the dewlap disappears gradually afterwards.<ref>{{Cite journal |last1=Hu |first1=C.-k. |last2=Frazier |first2=C. N. |date=1938-02-01 |title=Relationship Between Female Sex Hormone and Dewlap in the Rabbit |url=http://ebm.sagepub.com/lookup/doi/10.3181/00379727-38-9761 |journal=Experimental Biology and Medicine |language=en |volume=38 |issue=1 |pages=116–119 |doi=10.3181/00379727-38-9761 |s2cid=87987542 |issn=1535-3702}}</ref> Near the end of pregnancy, the female rabbit will pluck fur from the dewlap to line a nest for her young.<ref>{{Citation |last1=Vennen |first1=Kristine M. |date=2009-01-01 |journal=Manual of Exotic Pet Practice |pages=375–405 |editor-last=Mitchell |editor-first=Mark A. |place=Saint Louis |publisher=W.B. Saunders |language=en |doi=10.1016/b978-141600119-5.50017-2 |isbn=978-1-4160-0119-5 |pmc=7152457 |last2=Mitchell |first2=Mark A. |title=Rabbits |editor2-last=Tully |editor2-first=Thomas N.}}</ref>

==Reptiles and birds==
[[File:Blue-Eyed Anole, Corcovado Natl Park, Costa Rica.ogv|thumb|right|An anole lizard in Costa Rica repeatedly protracting and retracting its dewlap.]]
Many reptiles have dewlaps, most notably the anole family and [[Biology:Sitana|Sitana]] genus of [[Biology:Lizard|lizard]]s, which have large skin dewlaps they can extend and retract. The anole family has been found to have enhanced vision for color and depth perception.<ref>{{Cite journal|last=Sigmund|first=William R.|date=1983-01-01|title=Female Preference for Anolis carolinensis Males as a Function of Dewlap Color and Background Coloration|jstor=1563454|journal=Journal of Herpetology|volume=17|issue=2|pages=137–143|doi=10.2307/1563454}}</ref> This family is able to see dewlap coloration from a distance, giving the dewlap use and importance. These dewlaps are usually of a different color from the rest of their body and, when enlarged, make the lizard seem much bigger than it really is. The dewlap is primarily used when indicating territorial boundaries and for males to attract females during the mating season. The pigments generating this color are [[Chemistry:Pterin|pterin]]s and [[Biology:Carotenoid|carotenoid]]s. These two pigments are the most easily seen through the anole's eyes. Pterin and carotenoid pigments are located throughout the tissue of the dewlap, creating yellow and red hues.<ref>{{Cite journal|last1=Steffen|first1=John E.|last2=McGraw|first2=Kevin J.|date=2007-01-01|title=Contributions of pterin and carotenoid pigments to dewlap coloration in two anole species|journal=Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology|volume=146|issue=1|pages=42–46|doi=10.1016/j.cbpb.2006.08.017|pmid=17056290}}</ref> Lizards usually accompany dewlap movement with head bobs and other displays. The dewlap moves through extension and contraction. The muscles creating this movement are the ceratohyoid muscles and are connected to the [[Biology:Hyoid apparatus|hyoid apparatus]] in the throat and larynx area.<ref>{{Cite journal|last=Font|first=Enrique|date=1991-11-26|title=Localization of brainstem motoneurons involved in dewlap extension in the lizard, Anolis equestris|journal=Behavioural Brain Research|volume=45|issue=2|pages=171–176|doi=10.1016/S0166-4328(05)80082-8|pmid=1789924|s2cid=4031506}}</ref> Though the purpose of these displays is unclear, the colors of the dewlap and the movements during the displays are thought to be a way of standing out against visual background noise.

[[File:Iguana Dewlap Labeled.png|thumb|An iguana with an extended dewlap.]]
Many birds also have dewlaps, including domestic chickens, some cracids and some [[Biology:Guan (bird)|guans]].

==See also==
* Crest
* Double chin
* [[Biology:Neck frill|Neck frill]]
* [[Biology:Wattle (anatomy)|Wattle]]

==References==
{{Reflist}}

==External links==
* Weldon Owen Pty Ltd. (1993). ''Encyclopedia of animals&nbsp;— Mammals, Birds, Reptiles, Amphibians.'' Reader's Digest Association, Inc. {{ISBN|1-875137-49-1}}

[[Category:Skin anatomy]]

{{Sourceattribution|Dewlap}}