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

Revision as of 23:28, 6 February 2006

The mantle is an organ found in mollusks. 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 ectodermic 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 (CaCO₃). The individual crystals of each layer differ in shape and orientation. Nacre is continually deposited onto the inner surface of the animal's shell (the iridescent nacreous layer, also known as mother of pearl), both as a means to smoothen the shell itself and as a defense against 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 proteins.

Some shells may also contain pigments, which accounts for the fabulous colours of some seashells. These shell pigments may include compounds like pyrroles and porphyrins, 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 gills, anus, osphradium, nephridiopores, and gonopores. The mantle cavity may function as a respiratory chamber (all mollusks), feeding structure (bivalves), brood chamber (several forms), or locomotory organ (cephalopods 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.

The nervous system of cephalopods is the most complex of the invertebrates. The giant nerve fibers of the cephalopod mantle have been a favorite experimental material of neurophysiologists for many years.

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-[[image:nacre.jpg|thumb|200px|A piece of nacre]]
+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.
-[[image:Nacre_microscopic_structure.png|thumb|200px|A schematic of the microscopic structure of nacre, showing how the layers of aragonite platelets are separated by protein.]]
+== 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.
-'''Nacre''', also known as '''mother of pearl''' or '''sadaf''', is a naturally occuring organic-inorganic composite. It is formed of layers of [[calcium carbonate]] (CaCO<sub>3</sub>) platelets ([[crystals]]), in the form of [[aragonite]] and [[conchiolin]] (a [[scleroprotein]]), separated by [[elastic]] [[biopolymers]] (such as [[chitin]] and [[lustrin]]). This mixture of hard and elastic domains makes the material strong and resilient. Strength and resilience is also likely to be due to the offset or "brickwork" arrangement of the platelets, which inhibits transverse crack propagation.
+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.
-The [[iridescent]] appearance of the nacre is due to the fact that the thickness of the aragonite platelets are about 0.5 micron, which is comparable to the wavelength of visible light. This results in constructive and destructive [[interference]] of different wavelengths of light, resulting in different colors of light being reflected at different viewing angles.
+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.
-Nacre is secreted by the [[epithelial]] [[cell (biology)|cells]] of the [[Mantle (mollusc)|mantle tissue]] of certain species of [[mollusk]]. In these mollusks, nacre is continually deposited onto the inner surface of the animal's shell (the [[iridescent]] ''nacreous layer'', commonly known as ''mother of pearl''), both as a means to smooth the shell itself and as a defense against [[parasite|parasitic organisms]] and damaging detritus.
+== 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 iridescent inner layer is considered highly attractive by many cultures and is often used in making [[jewelery]] or as inlays in wood [[furniture]] and [[guitar]]s.
+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.
-When a mollusk is invaded by a [[parasite]] or is irritated by a foreign object that the animal cannot eject, a process known as ''[[encystation]]'' entombs the offending entity in successive, concentric layers of nacre. This process eventually forms what we call [[pearl]]s and continues for as long as the mollusk lives.
+The [[nervous system]] of cephalopods is the most complex of the [[invertebrate]]s. The giant [[nerve]] fibers of the cephalopod mantle have been a favorite experimental material of [[Neurophysiology|neurophysiologists]] for many years.
-Chief sources are the pearl [[oyster]], found in warm and tropical seas, primarily in [[Asia]]; freshwater pearl mussels, which live in many rivers of the [[United States]], [[Europe]], and Asia; and the [[abalone]] of [[California]], [[Japan]], and other [[Pacific Ocean|Pacific]] regions.
+Am I allowed to edit this?
-==Decorative uses==
-Tiles: Small, hand-cut shapes with straight edges, called 'tesserae', are laminated to either a [[marble]] or a [[ceramic]] base. The tesserae are hand placed and closely sandwiched together, creating an irregular mosaic or pattern (such as a weave). The laminated material is typically 1/16 of an inch thick.
-Sheets: Instead of using a marble or tile base, the mother of pearl tesserae are glued to a [[fiberglass]] mesh. The result is a lightweight material that offers a seamless installation, and there is no limit to the sheet size. Mother of pearl sheets may be used on interior floors, exterior and interior walls, countertops, doors and ceilings. Insertion into architectural elements, such as columns or furniture is easily accomplished.
-Both black and white mother of pearl are used for architectural purposes. The natural mother of pearl may be artificially tinted to almost any color.
-Mother of pearl is also used to clad porcelain sinks. Mother of pearl tesserae may be cut into artistic shapes and be laminated to ceramic tile and surrounded by numerous coats of colored lacquer to create an artistic design. The lacquer and the mother of pearl are polished at the same time, creating a durable, glossy hard surface.
-It is also available in thin laminated sheet form, allowing easy inlay and cladding work, and modern ceramic tiles.
-Shirt buttons were once often made of mother of pearl, though plastic has largely replaced its use.  Some of the finer quality clothing companies still use it, however.
-==Reference==
-*Lin, A., and Meyers, M.A. 2005. Growth and structure in abalone shell, ''Materials Science and Engineering A'' '''390'''(Jan. 15):27&#8211;41 ([http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXD-4DH2DRS-1&_coverDate=01%2F15%2F2005&_alid=256050522&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=5588&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=f4efd0a3d7cf3b4a0b8f9861cff4514d ])
-*Mayer, George, "Rigid Biological Systems as Models for Synthetic Composites", ''Science'' '''310''' (18 Nov 2005):1144&#8211;1147
-([http://www.sciencemag.org/cgi/content/abstract/310/5751/1144])
 == See also ==
-{{Wiktionary}}
+* [[Aperture (mollusc)|Aperture]]
-* [[Ammolite]]
+* [[Columella]]
+* [[Operculum]]
-[[Category:Mollusc products]]
+[[Category:Animal anatomy]]
-[[Category:Gemstones]]
+[[Category:Molluscs]]
-[[de:Perlmutt]]
+[[pt:Manto (molusco)]]
-[[fr:Nacre]]
-[[pl:Masa perłowa]]
-[[sv:Pärlemor]]