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

Revision as of 00:55, 15 August 2008

Template:Sea shell topics Template:Redirect Nacre, also known as mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer. It is exceptionally strong, resilient, and iridescent. Nacre is found in some bivalves, some gastropods and some cephalopods. The inner shell layer in most mollusks however is merely porcellaneous, in other words shiny like a china plate, not iridescent.

Pearls and the inside layer of the pearl oyster shells and the freshwater pearl mussel shells are made of nacre. Many other families of mollusks also have an inner shell layer which is nacreous, including gastropods such as the Haliotidae, the Trochidae and the Turbinidae.

Description

The iridescent nacre inside a Nautilus shell

Nacre is composed of hexagonal platelets of aragonite (calcium carbonate (CaCO₃) crystals) 10-20 µm wide and 0.5 µm thick, arranged in a continuous parallel lamina. These layers are separated by sheets of organic matrix composed of elastic biopolymers (such as chitin, lustrin and silk-like proteins). This mixture of brittle platelets and the thin layers of elastic biopolymers makes the material strong and resilient. Strength and resilience are also likely to be due to adhesion by the "brickwork" arrangement of the platelets, which inhibits transverse crack propagation. This design at multiple-length sizes increases its toughness enormously, making it almost equivalent to that of silicon.

Nacre appears iridescent because the thickness of the aragonite platelets 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.

Nacre is secreted by the epithelial cells of the mantle tissue of some species of mollusk. The nacre is deposited onto the inner surface of the shell, the iridescent nacreous layer, commonly known as mother of pearl. This smooths the shell and defends against parasites and damaging detritus by entombing them in successive layers of nacre, forming a pearl. The process is called is encystation and continues while the mollusk lives.

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 regions.

Decorative uses

Mother of pearl powder flask from circa 1750, mostly consisting of a polished Turbo marmoratus shell

Mother of pearl has been used over many centuries for all kinds of decorative purposes.

Inlay with nacre tesserae
Bagdad pavilion, Topkapı Palace, Istanbul

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 tesserae may be cut into shapes and laminated to a ceramic tile or marble 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. The tesserae are then lacquered and polished creating a durable, glossy hard surface.

Instead of using a marble or tile base, the mother of pearl tesserae can be 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.

Clothes & accessories

Mother of pearl buttons can be found on a variety of clothing such as shirts, skirts and coats. Nacre is also used as a decorative feature of watch faces, knives, guns and jewelry.

Musical instruments

Key touches and various decorations on musical instruments such as saxophones, trumpets, violins, banjos, tamburitzas and guitars are sometimes made of mother of pearl. It is used as inlays on many guitar fretboards.

Synthetic key touches made of Pyralin or similar imitation nacre materials have been affectionately referred to as mother of toilet seat by musicians.

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

Revision as of 00:55, 15 August 2008

Contents

Description

Decorative uses

Clothes & accessories

Musical instruments

References

See also

@@ Line 1: / Line 1: @@
-{{honor_header|3|1949|Nature|General Conference}}
+{{sea shell topics}}
+{{redirect|Mother of Pearl|the novel|Mother of Pearl (novel)}}
+'''Nacre''', also known as '''mother of pearl''', is an organic-inorganic [[composite material]] produced by some [[mollusk]]s as an inner [[seashell|shell]] layer.  It is exceptionally strong, resilient, and [[Iridescence|iridescent]].  Nacre is found in some [[bivalves]], some [[gastropods]] and some [[cephalopods]]. The inner shell layer in most mollusks however is merely porcellaneous, in other words shiny like a china plate, not iridescent.
-==1. Have the Shell Honor. ==
+[[Pearl]]s and the inside layer of the [[pearl oyster]] shells and the [[freshwater pearl mussel]] shells are made of nacre. Many other families of mollusks also have an inner shell layer which is nacreous, including gastropods such as the [[Haliotidae]], the [[Trochidae]] and the [[Turbinidae]].
-{{Ay prerequisite|Nature|Shells}}
-==2. Define the term "mollusca" or "mollusk." ==
-The word ''mollusc'' is derived from the French ''mollusque'', which originated from the Latin ''molluscus'', meaning thin-shelled, from ''mollis'', soft
-The body of a mollusk consists of three sections; a head, with eyes or tentacles; a muscular foot; and a visceral mass housing the organs.
+==Description==
+[[Image:NautilusCutawayLogarithmicSpiral.jpg|thumb|left|200px|The iridescent nacre inside a [[Nautilus]] shell ]]
+Nacre is composed of hexagonal platelets of [[aragonite]] ([[calcium carbonate]] (CaCO<sub>3</sub>) [[crystals]]) 10-20 [[µm]] wide and 0.5 µm thick, arranged in a continuous parallel lamina. These layers are separated by sheets of organic matrix composed of [[Elasticity (physics)|elastic]] [[biopolymers]] (such as [[chitin]], [[lustrin]] and [[silk]]-like [[protein]]s). This mixture of brittle platelets and the thin layers of elastic biopolymers makes the material strong and resilient. Strength and resilience are also likely to be due to adhesion by the  "brickwork" arrangement of the platelets, which inhibits transverse crack propagation. This design at multiple-length sizes increases its [[toughness]] enormously, making it almost equivalent to that of [[silicon]].
-==3. Learn the classification terms of mollusks, know the distinguishing characteristics of each, and become acquainted with several species under each class. ==
+Nacre appears [[iridescent]] because the thickness of the aragonite platelets 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.
-There are ten classes of molluscs; eight of the classes have living representatives, the other two classes are known only from fossils. More than 250,000 species of mollusc are recognized and named. Snails (Gastropoda) account for about 80% of living mollusc diversity.
-<center>
+Nacre is secreted by the [[epithelial]] [[cell (biology)|cells]] of the [[Mantle (mollusc)|mantle tissue]] of some species of [[mollusk]]. The nacre is deposited onto the inner surface of the shell, the iridescent ''nacreous layer'', commonly known as ''mother of pearl''.  This smooths the shell and defends against [[parasite]]s and damaging detritus by entombing them in successive layers of nacre, forming a [[pearl]].  The process is called is ''[[encystation]]'' and continues while the mollusk lives.
-{| border=1 cellpadding=5
-|width="110" | '''Class'''
-|width="300" | '''Major organisms'''
-|width="120" | '''Extant species'''
-|width="120" | '''Distribution'''
-|-
-| Caudofoveata     || worm-like organisms || 70 || deep ocean
-|-
-| Aplacophora      || solenogasters, worm-like organisms || 250 || deep ocean
-|-
-| Polyplacophora   || chitons || 600 || rocky marine shorelines
-|-
-| Monoplacophora   || limpet-like organisms || 11 || deep ocean
-|-
-| Gastropoda       || abalone, limpets, conch, nudibranchs, sea hares, sea butterfly, snails, slugs  || 150,000<ref>Ponder, Winston F. and Lindberg, David R. (Eds.) (2008) [http://www.ucpress.edu/books/pages/10802.php ''Phylogeny and Evolution of the Mollusca'']. Berkeley: University of California Press. 481 pp. ISBN 978-0520250925.</ref> || marine, freshwater, land
-|-
-| Cephalopoda      || squid, octopus, cuttlefish, nautilus || 786 || marine
-|-
-| Bivalvia         || clams, oysters, scallops, mussels || 8000 || marine, freshwater
-|-
-| Scaphopoda       || tusk shells || 350 || marine
-|-
-| Rostroconchia †  || fossils; probable ancestors of bivalves || extinct || —
-|-
-| Helcionelloida † || fossils; snail-like organisms such as ''Latouchella'' || extinct || —
-|-
-|}
-</center>
-==4 Distinguish between univalve and bivalve mollusks from the following considerations: ==
+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.
-===a. Shell   ===
-The terms ''univalve'' and ''bivalve'' refer to the configuration of the shells of the mollusks.  Univalves, such as snails, have shells consisting of one (thus ''uni-'') piece.  Bivalves, such as mussels, have shells consisting of two (thus ''bi-'') pieces hinged together.
-===b. Mollusk body  ===
+== Decorative uses ==
-;Univalves: Univalve bodies could almost be described as ''folded'' such that the mouth and anus both appear the the shell's opening.
+[[Image:Powder flask img 2091.jpg|thumb|left|Mother of pearl powder flask from circa 1750, mostly consisting of a polished ''[[Turbo marmoratus]]'' shell]]
-;Bivalves: Bivalves on the other hand, have flattened bodies.
+Mother of pearl has been used over many centuries for all kinds of decorative purposes.
-===c. Reproduction===
+[[Image:Istanbul.Topkapi046.jpg|thumb|right|200px|<center> Inlay with nacre tesserae </center> <br /> <small> Bagdad pavilion, [[Topkapı Palace]], [[Istanbul]]</small>]]
-;Univalves: All land snails are hermaphrodites, producing both spermatozoa and ova. In other words, each individual is both male and female.  Some freshwater snails, such as Apple Snails, and marine species, such as periwinkles, have separate sexes; they are male and female. Most snails can mate when they are around 1 year old.
+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 [[:wikt:tessera|tesserae]] may be cut into shapes and laminated to a [[ceramic]] [[tile]] or [[marble]] 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.  The tesserae are then lacquered and polished creating a durable, glossy hard surface.
-:Prior to reproduction, most land snails perform a ritual courtship before mating. This may last anywhere between two and twelve hours. Prolific breeders, pulmonate land snails inseminate each other in pairs to internally fertilize their ova. Each brood may consist of up to 100 eggs.
+Instead of using a marble or tile base, the mother of pearl tesserae can be 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.
-:Pulmonate land snails and slugs have a reproductive opening on one side of the body, near the front, through which the outer reproductive organs are extruded so that exchange of sperm can take place. After this, fertilization occurs and the eggs develop.
+=== Clothes & accessories ===
+[[Image:Masa perłowa3.jpg|thumb|left]]
-:Garden snails bury their eggs in shallow topsoil primarily while the weather is warm and damp, usually 5 to 10 cm down, digging with their foot. Egg sizes differ between species, from a 3 mm diameter in the grove snail to a 6 cm diameter in the Giant African Land Snail. After 2 to 4 weeks of favorable weather, these eggs hatch and the young emerge. Snails may lay eggs as often as once a month.
+Mother of pearl buttons can be found on a variety of clothing such as shirts, skirts and coats.  Nacre is also used as a decorative feature of watch faces, knives, guns and jewelry.
-;Bivalves: In bivalves, the sexes are usually separate, but some hermaphroditism is known. Bivalves practice external fertilization.  External fertilization is a form of fertilization in which a zilo cell is united with an egg cell external to the body of the female. Thus, the fertilization is said to occur "externally". This is distinct from internal fertilization where the union of the egg and sperm occur inside the female after insemination through copulation.
+=== Musical instruments ===
+Key touches and various decorations on musical instruments such as [[saxophone]]s, [[trumpet]]s, [[violin]]s, [[banjos]], [[tamburitza]]s and [[guitar]]s are sometimes made of mother of pearl. It is used as inlays on many guitar fretboards.
-:In sexual reproduction, there must be some way of getting the sperm to the egg. Since sperm are designed to be mobile in a watery environment, aquatic mollusks can make use of the water in which they live. Eggs and sperm are simultaneously shed into the water, and the sperm swim through the water to fertilize the egg in a process known as broadcast fertilization.
+Synthetic key touches made of [[Pyralin]] or similar imitation nacre materials have been affectionately referred to as ''mother of [[toilet seat]]'' by musicians.
-===d. Movements===
+==References==
-[[Image:Snail climbing grass SMC 07.jpg|thumb|250px|right|Snail climbing a blade of grass]]
+* {{cite journal
-;Univalves: Most snails move by gliding along on their muscular foot, which is lubricated with mucus. This motion is powered by succeeding waves of muscular contraction which move down the undersurface of the foot. This muscular action is clearly visible when a snail is crawling on the glass of a window or aquarium. Snails move at a proverbially low speed (1 mm/s is a typical speed for adult ''Helix lucorum''). They produce mucus in order to aid locomotion by reducing friction, and the mucus also helps reduce the snail's risk of mechanical injury from sharp objects. This means that they can 'walk' over sharp objects like razors without being injured.
+| first = A.
+| last = Lin
-;Bivalves: Razor shells (''Ensis spp.'') can dig themselves into the sand with great speed to escape predation. Scallops can swim to escape an enemy, clapping their valves together to create a jet of water. Cockles can use their foot to leap from danger. However these methods can quickly exhaust the animal. In the razor shells the siphons can break off only to grow back later.
+| coauthors = Meyers, M.A.
-{{clear}}
+| date = 2005-01-15
+| title = Growth and structure in abalone shell
-===e. Securing food===
+| journal = [[Materials Science and Engineering]] A
-;Bivalves: Bivalves are unique among the molluscs for lacking a radula; they feed by siphoning and filtering large particles from water.
+| volume = 390
+| pages = 27&ndash;41
-;Univalves: Univalves include some that are herbivores, detritus feeders, predatory carnivores, scavengers, parasites, and also a few ciliary feeders, in which the radula is reduced or absent. The radula of a univalve is usually adapted to the food that a species eats. The simplest univalves are the limpets and abalones, herbivores that use their hard radulas to rasp at seaweeds on rocks.  Many marine univalves are burrowers, and have soft siphons or tubes that extend from the mantle. Sometimes the shell has a siphonal canal to accommodate this structure. A siphon enables the animal to draw a small flow of water into their bodies. The siphon is used primarily to "taste" the water, in order to detect prey from a distance. Univalves with siphons tend to be either predators or scavengers.
+| url = 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
+| doi = 10.1016/j.msea.2004.06.072
-===f. Self-preservation===
+}}
-;Univalves: When retracted into their shells, many snails with gills (including many marine, some freshwater and some terrestrial species) are able to protect themselves with a door-like anatomical structure called an operculum.  Some snails hibernate during the winter (typically October through April in the Northern Hemisphere). They may also estivate in the summer in drought conditions. To stay moist during hibernation, a snail seals its shell opening with a dry layer of mucus called an epiphragm.
+* {{cite journal
+| first = G.
-;Bivalves:  The radical structure of the bivalves affects their behaviour in several ways. the most significant is the use of the closely-fitting valves as a defence against predation and, in intertidal species such as mussels, drying out. The entire animal can be contained within the shell, which is held shut by the powerful adductor muscles. This defence is difficult to overcome except by specialist predators such as the Starfish and Oystercatcher.  The file shells (''Limidae'') can produce a noxious secretion when threatened, and the fan shells of the same family have a unique, acid-producing organ.
+| last = Mayer
+| year = 2005
-==5. Identify from shells or drawings and know the meaning of the following concho logical terms: ==
+| doi =  10.1126/science.1116994
-===a. Valve  ===
+| title = Rigid biological systems as models for synthetic composites
-===b. Apex   ===
+| journal = Science
-The apex is a word most often used to mean the tip of the spire of the shell of a gastropod. It is the first-formed, and therefore the oldest, part of the shell. To be more precise, the apex would usually be where the tip of the embryonic shell or protoconch is situated, if that is still present in the adult shell.
+| volume = 310
+| pages = 1144&ndash;1147
-The word apex can also be used to refer to a similar part in other molluscan shells, however, the apex of bivalves is more usually known as the umbos, beaks or prodissoconch.
+| pmid = 16293751
+}}
-The apex of tusk shells is the small, open posterior end, and the opening itself is usually called the apical aperture.
+* {{cite journal
+| last = Bruet
-The phrase apical whorls, or protoconch, means the whorls of the embryonic shell at the apex of the shell, especially when this is clearly distinguishable from the later whorls of the shell, otherwise known as the teleoconch.
+| first = B.
+| coauthors = ''et al.''
-The space under the apex of a patellate gastropod is called the apical cavity.
+| year = 2005
+| month = September
-===c. Aperture ===
+| title = Nanoscale morphology and indentation of individual nacre tablets from the gastropod mollusc ''Trochus niloticus''
-[[Image:Semicassis pyrum (base).JPG|thumb|250px|''Semicassis pyrum'', which has a large aperture.]]
+| journal = J. Mater. Res.
-The aperture is the main (or only) opening in the shell of a gastropod or snail. It is where the soft parts of the animal emerge. In some prosobranch gastropods, the aperture is able to be closed, and even completely sealed, with a sort of door or operculum.
+| volume = 20
+| issue = 9
-The aperture of many snail shells is round, rounded, elliptical or oval. This shape corresponds roughly to the cross-section of the body whorl of the shell.
+| url = http://web.mit.edu/cortiz/www/Ben/BenPaperRevisedFinal.pdf
+| doi = 10.1557/JMR.2005.0273
-The aperture of a snail shell can have many other forms: semicircular, trilobate or auriculate. In some gastropods, the aperture is narrowed by protruding shell folds or "bacon", which help make the soft parts of the animal less vulnerable to predation.
-For convenience of reference, the apertural edge or margin of a gastropod shell is divided into three areas or walls:
-* The parietal wall: the area next to the penultimate whorl of the shell
-* The columellar wall: the wall next to the columella
-* The palatal wall: the outer free wall of the final whorl of the shell
-===d. Byssus   ===
-[[Image:Zebra mussel GLERL 1.jpg|left|thumb|byssus threads on ''Dreissena polymorpha'']]
-Mussels use byssus to attach to rocks and other surfaces. When a mussel's foot encounters a crevice, it creates a vacuum chamber by forcing out the air and arching up, similar to a plumber's plunger unclogging a drain. The byssus, made of keratin and other proteins, is spewed into this chamber, and bubbles into a sticky foam. By curling its foot into a tube and pumping the foam, the mussel produces sticky threads about the size of a human hair. It varnishes the threads with another protein, resulting in an adhesive.
-Byssus is a remarkable adhesive that is neither degraded nor deformed by water as are synthetic adhesives. This has spurred genetic engineers to insert mussel DNA into yeast cells for translating the genes into the appropriate proteins.
-===e. Foot  ===
-===f. Mantle  ===
-[[Image:Loligo vulgaris.jpg|250px|thumb|European Squid (''Loligo vulgaris''). The mantle is all that is visible behind the head.]]
-The mantle is an important part of the anatomy of molluscs. It is the dorsal body wall which covers the visceral mass.
-In many, but by no means all, species of molluscs, the epidermis of the mantle secretes calcium carbonate and creates a shell.
-The word "mantle" (a old word, meaning cloak) is used for this anatomical structure because in many kinds of molluscs, the edge of the mantle extends beyond the main part of the body, forming flaps or double-folded structures.
-{{clear}}
-===g. Operculum===
-[[Image:Viviparus contectus met operculum2.JPG|right|thumb|Gastropod shell of ''Viviparus contectus'' with operculum]]
-The operculum, meaning little lid, (plural: opercula or operculums) is a corneous or calcareous structure which exists in some groups of marine, freshwater, and land snails or gastropods. It is present in most but not all gastropods that have shells and gills. Pulmonate snails do not have have opercula, but some terrestrial species are capable of secreting an epiphragm.
-In its most typical condition, an operculum serves to close the opening or aperture of the shell when the soft parts of the animal are withdrawn into the shell.
-An operculum can vary in shape greatly from one family of gastropods to another, but an operculum is fairly often circular, or more or less oval in shape. In species where the operculum fits snugly, its outline corresponds exactly to the shape of the aperture of the shell.
-{{clear}}
-===h. Mother of pearl===
-===i. Epidermis===
-===j. Ribs===
-===k. Teeth===
-===l. Concentric lines===
-===m. Canal===
-===n. Spines===
-===o. Whorls===
-===p. Lips===
-==6. Explain the development of a shell. How long do mollusks live?==
-<gallery perrow=3 widths=200>
-Image:Cypraea chinensis with partially extended mantle.jpg|The marine gastropod ''Cypraea chinensis'', the Chinese Cowry, showing partially extended mantle
-Image:Giant_clam_or_Tridacna_gigas.jpg|The giant clam (''Tridacna gigas'') is the largest extant bivalve
-Image:A fossil shell with calcite.jpg|Fossil shell covered in calcite crystals
-</gallery>
-In those mollusks which have a shell, the shell grows gradually over the lifetime of the mollusc by the addition of calcium carbonate to the leading edge or opening, and thus the shell gradually becomes longer and wider, in an increasing spiral shape, to better accommodate the growing animal inside. The animal also thickens the shell as it grows, so that the shell stays proportionately strong for its size.
-A mollusk shell is formed, repaired and maintained by a part of the anatomy called the mantle. Any injuries to or abnormal conditions of the mantle are usually reflected in the shape and form and even color of the shell. When the animal encounters harsh conditions which limit its food supply, or otherwise cause it to become dormant for a while, the mantle often ceases to produce the shell substance. When conditions improve again and the mantle resumes its task, a "growth line" which extends the entire length of the shell is produced, and the pattern and even the colors on the shell after these dormant periods are sometimes quite different from previous colors and patterns.
-Interestingly, within some species of mollusk there is often a surprising degree of variation in the exact shape, pattern, ornamentation, and color of the shell.
-The longest lived mollusk is the ''Arctica islandica'' (Ocean Quahog).  Animals of this species close to 400 years old are not uncommon.
-==7. Give some facts about the life of a strombus pugilis (fighting conch) and explain why this shell is so named. ==
-==8. Explain the activities of the shipworm. ==
-{{:Adventist Youth Honors Answer Book/Nature/Shipworm}}
-==9. What accounts for the distribution of mollusks.==
-==10. Name two mollusks that have no shells. ==
-<gallery>
-Image:Unknown slug on rhubarb.jpg|<center>Slug</center>
-Image:Octopus in sea life Helsinki.jpg|<center>Octopus</center>
-Image:Cuttlefish.jpg|<center>Cuttlefish</center>
-Image:Mastigoteuthis flammea.jpg|<center>Squid</center>
-</gallery>
-==11. Find answers for the following interesting questions: ==
-===a. How are bivalve and univalve animals fastened to their shells? ===
-===b. How is shell color controlled? ===
-[[Image:Nautilus profile.jpg|thumb|300px|The Nautilus, a mollusk with four gills]]
-===c. What mollusk has four gills? ===
-The '''Nautilus'' has two pairs of gills (that's four!).
-===d. From what sea animal was India ink formerly made? ===
-Cuttlefish have ink, like squid and octopuses. This ink was formerly an important dye, called sepia. Today artificial dyes have replaced natural sepia.
-===e. What mollusk spins a silken thread? ===
-Several mollusks spin a ''byssus'' which is used to anchor them to a substrate.  These include mussels in the family ''Mytilidae'' and the zebra mussel (''Dreissena polymorpha'').  However, the mollusk with perhaps the most extensive byssus is the '''rigid pen shell''' (''Atrina rigida'').  Like most pen shells, ''A. rigida'' lives in soft bottoms, with the majority of the shell buried, point down, leaving only a few inches exposed, held in place by an extensive net of byssal threads.
-===f. What shells were used for money by ancient tribes? ===
-Many people find the very rounded, shiny, porcelain-like shells of '''cowries''' pleasing to look at and to handle. Shells of certain species have historically been used as currency in several parts of the world, as well as being used, in the past and present, very extensively in jewelry, and for other decorative and ceremonial purposes.
-===g. What shell is considered sacred by the Tibetans? ===
-Tibetan Buddhists make use of a particular set of eight auspicious symbols, ''ashtamangala'', in household and public art. The '''chank shell''' or '''conch''' is one of these eight symbols:
-# Conch
-# Knot
-# Fish
-# Banner
-# Lotus
-# Parasol
-# Urn
-# Wheel
-===h. Purple dye of ancient times came from the secretion of what mollusk? ===
+| pages = 2400}}
-''Hexaplex trunculus'' (also known as ''Murex trunculus'' or the '''banded dye-murex''') is a medium-sized species of sea snail.
-This species of sea snail is important historically because its hypobranchial gland secretes a mucus that the ancient Canaanites/Phoenicians used as a distinctive purple-blue indigo dye. One of the dye's main chemical ingredients is indigotin, and if left in the sun for a few minutes before becoming fast, its color turns to a blue indigo (like blue jeans).
+==See also==
+{{Commonscat|Mother of pearl}}
+{{Wiktionary}}
+* [[Ammolite]]
+* [[Pearl]]
+* [[Raden]]
-===i. What is the source of pearls? How are they formed? ===
+[[Category:Mollusc products]]
-Nacre, also known as mother of pearl, is an important part of the shell structure in many gastropod and bivalve mollusks especially the more ancient families such as top shells and pearl oysters. Like the other calcareous layers of the shell, the nacre is created by the epithelial cells (formed by the germ layer ectoderm) of the mantle tissue. Mollusk blood is rich in dissolved calcium, and during shell deposition, the calcium is concentrated out from the blood and crystallized as calcium carbonate. Nacre is continually deposited onto the inner surface of the animal's shell (the iridescent nacreous layer or mother of pearl). This is done both as a means to thicken, strengthen and smooth the inner surface of the shell itself and as a defense against parasitic organisms and damaging detritus.
+[[Category:Pearls]]
-When a mollusc 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 inner shell material, which in some cases is nacre. This process eventually forms what we call pearls and continues for as long as the mollusk lives. Almost any species of bivalve or gastropod is capable of producing "pearls", even mollusks which have no inner nacreous layer. However, only a few species, such as the famous pearl oysters, can create pearls which are highly prized.
-==12. Name six commercial uses for shells. ==
-;Musical Instruments: Key touches and various decorations on musical instruments such as saxophones, trumpets, violins, banjos, tamburitzas and guitars are sometimes made of mother of pearl. It is used as inlays on many guitar fretboards.
-;Clothing: Mother of pearl buttons can be found on a variety of clothing such as shirts, skirts and coats.
-;Decorative Inlays: Nacre is also used as a decorative feature of watch faces, knives, guns and jewelry.
-;Building Material: Instead of using a marble or tile base, the mother of pearl tesserae can be 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.  Conch shells are occasionally used as a building material, either in place of bricks or as bulk for landfill.
-;Jewelry: Pearls are highly prized jewelry components.
-;Souvenirs: In some countries, cleaned Queen Conch (''Strombus gigas'') shells or polished fragments are sold, mainly to tourists, as souvenirs or in jewelry. Without a permit, however, export is a breach of CITES regulations and may lead to arrest. This is most likely to occur on return to the tourist's home country while clearing customs. In the UK conch shells are the ninth most seized import.
-;Pets: Snails are often kept in aquariums along with fish.
-==13. Do one of the following: ==
-===a. Personally find and collect 40 species of shells representing the five classifications. List each shell as to the place and date it was found, common name, scientific name, and class. ===
-===b. Make a collection of 50 species of shells you have found, received, or purchased representing the five classifications. List each shell collected as follows: if personally found, give the information called for under letter "a" above; if received or purchased, give the name of the person from whom the shell was received, the habitat of the shell, the date of its acquisition, and its common name, scientific name, and class.===
-==References==
-* http://depts.washington.edu/natmap/mollusks/glossary.html
-* http://www.informaworld.com/smpp/content~content=a793157051~db=all~jumptype=rss
-[[Category:Adventist Youth Honors Answer Book|{{SUBPAGENAME}}]]
+[[bg:Седеф]]
+[[da:Perlemor]]
+[[de:Perlmutt]]
+[[es:Nácar]]
+[[eo:Perlamoto]]
+[[fr:Nacre]]
+[[it:Madreperla]]
+[[he:אם הפנינה]]
+[[lt:Perlamutras]]
+[[mn:Тана]]
+[[nl:Parelmoer]]
+[[no:Perlemor]]
+[[pl:Masa perłowa]]
+[[pt:Madrepérola]]
+[[ru:Перламутр]]
+[[sv:Pärlemor]]
+[[vi:Xà cừ (vật liệu)]]
+[[tl:Binga]]