The vocal sac is the flexible
membraneof skin possessed by most male frogs. The purpose of the vocal sac is usually as an amplification of their mating or advertisement call. The presence or development of the vocal sac is one way of externally determining the sex of a frog in many species.
The structure and location of the vocal sac is dependent on the species. There are three main types of vocal sac. The most common, is one large vocal sac located under the chin, called "median subgular". The other two types of vocal sac consist of two separate vocal sacs. The more common of these is two vocal sacs on the edge of the chin, called "paired lateral". The last, and least common, is two separate vocal sacs under the chin, called "paired subgular". All three types have species which inflate internall and externally. If they are inflated externally, the vocal sac can usually be clearly seen. If inflated internally, the body will look inflated. Usually, species which inflate their vocal sacs internally call from within the water or ground where lower frequencies travel better. Also, aquatic frogs would have problems with
buoyancyif the vocal sacs inflated externally.
The vocal sac is open to the mouth cavity of the frog, with two slits on either side of the tongue. To call, the frog inflates its lungs.Clarifyme|date=October 2007 The air is then expelled from the lungs, through the
larynx, and into the vocal sac. The vibrations of the larynx emits a sound, which resonates within the vocal sac. The resonance causes the sound to be amplified, and allows the call to carry further. Muscles within the body wall force the air back and forth between the lungs and vocal sac. The frogs mouth and nose are kept shut for the duration of the call.
The development of the vocal sac is different in most species, however they mostly follow the same line. The development of the unilobular vocal sac begins with two small growths on the floor of the mouth. They begin to grow, until they form two small pouches. The pouches expand until they meet in the centre of the mouth, and form one large cavity, which grows until it is fully developed.
The primary purpose of the vocal sac is to amplify the advertisement call of the male, and attract females from as large an area as possible. Species of frog without vocal sacs may only be heard within a radius of a few metres, whereas some species with vocal sacs can be heard over convert|1|km|mi|abbr=on away. Modern frog species (
Neobatrachians and some Mesobatrachians) which lack vocal sacs tend to inhabit areas close to flowing water. The sound of the flowing water overpowers the advertisement call, so they must advertise by other means.
An alternative use of the vocal sac, is that employed by the frogs of the
Rhinodermatidaefamily. The males of the two species of this family will scoop recently hatched tadpoles into their mouth, where they will move into the vocal sac. The tadpoles of Darwin's Frog("Rhinoderma darwinii") will remain in the vocal sac until metamorphisis, whereas the Chile Darwin's Frog("Rhinoderma rufum") will transport the tadpoles to a water source.
*cite book| last=Tyler| first=M. J.| year=1994| title=Australian Frogs A Natural History| publisher=Reed Books| id=ISBN 0-7301-0468-0
*cite web| title = The Seattle Times: Natural Wonders| url=http://seattletimes.nwsource.com/news/local/naturalwonders/links/chorusfrog.html| accessdate=2006-06-15
*cite book| last=Cogger|first=H.G.|coauthors=R.G. Zweifel, and D. Kirschner| year=2004| title=Encyclopedia of Reptiles & Amphibians Second Edition| publisher=Fog City Press| id=ISBN 1-877019-69-0
*cite book| last=Duellman| first=Willam E.| title=Biology of Amphibians| publisher=The Johns Hopkins University Press| year=1994| coauthors=Linda Truels| id=ISBN 080184780X
*cite web| title=Anurans - Vocal| url=http://cal.man.ac.uk/student_projects/2000/mnzo7cas/vocal.htm| accessdate=2006-06-19
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vocal sac — ▪ amphibian anatomy the sound resonating throat pouch of male frogs (frog) and toads (toad) (amphibians (amphibian) of the order Anura). Vocal sacs are outpocketings of the floor of the mouth, or buccal cavity. Frogs display three basic types… … Universalium
vocal sac — noun also vocal pouch : one of a pair of inflatable resonating sacs in the mouth of various frogs; also : the unpaired sac in the true toads of the genus Bufo … Useful english dictionary
vocal sac — noun The flexible membrane of skin possessed by most male frogs … Wiktionary
vocal pouch — noun see vocal sac … Useful english dictionary
Sac vocal — (Litoria chloris). Le sac vocal est un sac gulaire destiner à amplifier les sons par la formation d une caisse de résonance. Cet organe constitué de la membrane souple de peau extensible est présent chez les mâles de la plupart des anoures mâles … Wikipédia en Français
Vocal fold cyst — Vocal fold cysts are collections of fluid in sac like formations on the vocal folds.Cysts can deteriorate the quality of human speech production, causing diplophonia, a condition where the vocal cords produce multiple tones at the same time, or… … Wikipedia
Sac gulaire — d une Frégate superbe Le sac gulaire est une poche membraneuse dilatable visible sur la gorge de certaines espèces comme les pélicans, les marabouts et les frégates. Leur utilisation dépend de l espèce, ceux utilisés pour amplifier les sons sont… … Wikipédia en Français
sac — 1. sac [ sak ] n. m. • 1050 « étoffe grossière »; lat. saccus, gr. sakkos, d o. sémitique I ♦ A ♦ 1 ♦ (1120) Contenant formé d une matière souple pliée, assemblée, et ouvert seulement par le haut. ⇒ 1. poche. Grand, petit sac (⇒ sachet) . Sac… … Encyclopédie Universelle
Vocal folds — Infobox Anatomy Name = Vocal folds Latin = plica vocalis GraySubject = 236 GrayPage = 1079 Caption = Laryngoscopic view of the vocal folds. Caption2 = Abduction and adduction Precursor = |Sixth pharyngeal arch System = Artery = Vein = Nerve = |N … Wikipedia
croaking sac — noun : vocal sac … Useful english dictionary