Difference between revisions of "AY Honors/Shells - Advanced/Answer Key"

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The '''mantle''' is an organ found in [[mollusk]]s. It is the dorsal body wall covering the main body, or visceral mass. The [[epidermis]] of this organ secretes [[calcium carbonate]] to create a shell.
 
 
== Shell formation ==
 
  
[[Nacre]] is secreted by the [[germ layer|ectodermic]] [[cell (biology)|cells]] of the mantle tissue of most mollusks. Mollusk [[blood]] is rich in a liquid form of [[calcium]]. In these mollusks the calcium is concentrated out from the blood where it can crystallize as calcium carbonate (CaCO<sub>3</sub>). The individual crystals of each layer differ in shape and orientation. Nacre is continually deposited onto the inner surface of the animal's [[animal shell|shell]] (the [[iridescent]] ''nacreous layer'', also known as ''[[Nacre|mother of pearl]]''), both as a means to smoothen the shell itself and as a defense against [[parasite|parasitic organisms]] and damaging detritus.
 
 
The calcium carbonate layers are generally of two types: an outer, chalk-like prismatic layer and an inner pearly, lamellar or nacreous layer. The layers may incorporate a substance called [[conchiolin]], often in order to help bind the calcium carbonate crystals together. Conchiolin is composed largely of [[quinone]]-tanned [[protein]]s.
 
 
Some shells may also contain pigments, which accounts for the fabulous colours of some [[seashell]]s. These shell pigments may include compounds like [[pyrrole]]s and [[porphyrin]]s, which are also proteins.
 
 
== The mantle cavity ==
 
A mantle skirt is a double fold of mantle that encloses a water space. This space is called the ''mantle cavity'', and it is a central feature of mollusk biology, containing the mollusk's [[gill]]s, [[anus]], [[osphradium]], [[nephridiopore]]s, and [[gonopore]]s. The mantle cavity may function as a [[Respiration (physiology)|respiratory]] chamber (all mollusks), feeding structure ([[bivalve]]s), brood chamber (several forms), or locomotory organ ([[cephalopod]]s and some bivalves).
 
 
The mantle is highly muscular. In cephalopods it is used to force water through a tubular siphon, the [[hyponome]], to propel the animal quickly through the water. In other mollusks, it is used as a kind of "foot" for locomotion.
 
 
== See also ==
 
* [[Aperture (mollusc)|Aperture]]
 
* [[Columella]]
 
* [[Operculum (gastropod)|Operculum]]
 
 
[[Category:Animal anatomy]]
 
[[Category:Molluscs]]
 
 
[[pt:Manto (molusco)]]
 

Revision as of 02:25, 21 April 2006