Moult 317695 226113588 2008-07-16T21:45:40Z XLinkBot 6163802 BOT--Reverting edits by [[:en:Special:Contributions/Christobello|Christobello]] to revision 226105391 (\byoutube\.com) {{Refimprove|date=July 2007}} {{otheruses}} In [[biology]], '''moulting''' (or '''molting''',<ref>"Molting" vs. "moulting" -- see [[American and British English spelling differences#Miscellaneous spelling differences|spelling differences]].</ref> also known as '''shedding''' or for some species, '''[[ecdysis]]''') signifies the manner in which an animal routinely casts off a part of its body (often but not always an outer layer or covering), either at specific times of year, or at specific points in its life-cycle. Moulting can involve the [[Epidermis (skin)|epidermis]] (skin), [[hair]] or [[fur]], or other external layer. In some species, other body parts may be shed, for example, [[wing]]s in some [[insect]]s. Examples include old [[feather]]s in [[bird]]s, old [[hair]]s in [[mammal]]s (especially [[dog]]s and other [[canidae]]), old [[skin]] in [[reptile]]s, and the entire [[exoskeleton]] in [[arthropod]]s. ==Examples== {| class="wikitable" ! Species ! Item shed ! Timing ! Known as ! Notes |- | [[Dog]]s and other [[canid]]s | [[Hair]] ([[Fur]]) | Semi-annually, spring and fall | Shedding | Seasonal temperature variations influence shedding; some shed all year, some shed specifically twice a year. |- | [[Snake]]s | [[Skin]] | Regularly, when old skin is outgrown | Moulting | &nbsp; |- | [[Lizard]]s | [[skin]] | Regularly, when old skin is outgrown | Moulting | Lizards consume their shed skin for calcium, grooming, and other nutrients |} ==Specific species notes== ===Birds=== In [[bird]]s, moulting is the periodic replacement of [[feather]]s by shedding old feathers while producing new ones. Feathers are dead structures at maturity, and they become gradually worn down and need to be replaced. Adult birds moult at least once a year, though many moult twice, and a few three times.<ref name="Terres"/> It is a comparatively slow process, as a bird never sheds all its feathers at once; it must keep enough of its feathers to regulate its body temperature and repel moisture. The amount of shed feathers varies. In some moulting periods, a bird may renew only the feathers on the head and body, shedding the wing and tail feathers during a later moulting period.<ref name="Terres"/> Some species of wild bird become flightless during an annual "wing moult" and must seek protected habitat with a reliable food supply during that time. A moulting bird should never have any bald spots. If a pet bird has any bald spots, the bird should be taken to an [[avian veterinarian]] to search for possible causes for the baldness, which may include [[giardiasis]], [[mites]], or [[feather-plucking]]. <!-- "In a nutshell, species that follow the Complex Alternate Strategy have two molts per year as an adult and three molts in their first year of life (also called their first plumage-cycle)." - from Chipping Sparrow article --> The process of moulting in birds is as follows: First, the bird begins to shed some old feathers, then [[pin feathers]] grow in to replace the old feathers. As the pin feathers become full feathers, other feathers are shed. This is a cyclical process that occurs in many phases. In general, a moult begins at a bird's head, progresses down the body to its wings and torso, and finishes with the tail feathers. It is usually [[symmetrical]], with feather loss equal on each side of the body.<ref name="Terres">{{cite book| last =Terres| first =J. K.| authorlink =John Kenneth Terres| title =The Audubon Society Encyclopedia of North American Birds| publisher =Knopf| date =1980| location =New York, NY| pages = 616-617| isbn = 0394466519 }}</ref> Because feathers make up 4-12 percent of a bird's body weight, it takes a large amount of energy to replace them. For this reason, moults are frequently timed to occur right after the breeding season, but while food is still abundant. The plumage produced during this time is called postnuptial plumage.<ref name="Terres"/> ===Canidae=== {{main|Coat (dog)}} [[Dog]]s and other [[canid]]s routinely shed their fur twice a year, in the spring and fall. Seasonal temperature variations influence shedding; some shed all year, some shed specifically twice a year. ===Reptiles=== [[Image:SnakeSkin.JPG|thumb|Moulted Snake Skin]] The most familiar example of moulting in [[reptile]]s is when [[snake]]s "shed their skin". This is usually achieved by the snake rubbing its head against a hard object, such as a rock (or between two rocks) or piece of wood, causing the already stretched [[skin]] to split. At this point, the snake continues to rub its skin on objects, causing the end nearest the head to peel back on itself, until the snake is able to crawl out of its skin, effectively turning the moulted skin inside-out. This is similar to how you might remove a [[sock]] from your [[foot]] by grabbing the open end and pulling it over itself. The snake's skin is often left in one piece after the moulting process. Conversely, [[lizard]]s' skins fall off in pieces. ===Arthropods=== {{main|Ecdysis}} [[Image:Cicada molting animated-2.gif|thumb|right|''[[Tibicen]]'' Dog Day Cicada moulting (time lapse video)]] In [[arthropod]]s, such as [[insect]]s, [[arachnid]]s and [[crustacean]]s, moulting is the shedding of the [[exoskeleton]] (which is often called its [[Animal shell|shell]]), typically to let the organism grow. This process is called [[ecdysis]]. Ecdysis is necessary because the exoskeleton is rigid and cannot grow like [[skin]]. The new exoskeleton is initially soft but hardens after the moulting of the old exoskeleton. The old exoskeleton is referred to as an "[[exuvium]]" (or exuvia). ==References== {{Reflist}} [[Category:Developmental biology]] [[bs:Linjanje]] [[bg:Линеене]] [[de:Häutung]] [[de:Mauser (Vögel)]] [[eo:Mudo]] [[fr:Mue des oiseaux]] [[hr:Mitarenje]] [[it:Muta (biologia)]] [[lt:Šėrimasis]] [[nl:Rui (ornithologie)]] [[no:Myting]] [[pl:Linienie]] [[ru:Линька]] [[sl:Levitev]] [[sr:Митарење]] [[sh:Mitarenje]] [[sv:Ruggning (biologi)]] [[zh:换羽]]