A seashell is the common name for a hard, protective outer layer created by a marine organism or sea creature. Marine is an Umbrella term. As an adjective it is usually applicable to things relating to the Sea or Ocean, such as Marine biology, Marine In addition to seashells, there are also several different types of non-marine animal shell in the natural world.
Seashells are very often found in beach drift, which is deposited along strandlines on beaches. These shells are often washed up empty and clean, the animal having already died, and the soft parts having rotted away or having been eaten by other creatures. This is how most shells are found by beachcombers, and collecting these shells is a harmless hobby. Beachcombing or Beachcomber is a term with multiple but related meanings which have evolved over time However, the majority of seashells which are offered for sale commercially have been collected live, killed and cleaned specifically for the commercial trade, and this type of exploitation can sometimes have a strong negative impact on rarer species, and on local ecosystems. An ecosystem is a natural unit consisting of all plants animals and micro-organisms( Biotic factors in an area functioning together with all of the non-living physical (
The kind of seashells which are perhaps most familiar, and most commonly encountered, both in the wild and for sale as decorative objects, are the external shells of marine mollusks. Marine is an Umbrella term. As an adjective it is usually applicable to things relating to the Sea or Ocean, such as Marine biology, Marine Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 These are usually primarily composed of calcium carbonate, in the form of calcite or aragonite crystallised out in an organic matrix. Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3 Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Aragonite is a Carbonate mineral, one of the two common naturally occurring polymorphs of Calcium carbonate, Ca[[carbon C]] O 3 Calcium carbonate in mollusk shells can take different crystalline forms, one being nacre, otherwise known as mother of pearl. Nacre, also known as mother of pearl, is an organic-inorganic Composite material produced by some Mollusks as an inner shell layer
Other kinds of sea animals have exoskeletons or shells which may after death be found in beach drift and picked up by beachcombers, and these include other invertebrate remains such as crab shells, horseshoe crab shells, and sea urchin tests. An exoskeleton is an external Skeleton that supports and protects an animal's body in contrast to the internal Endoskeleton of for example a Human. An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy The horseshoe crab or Atlantic horseshoe crab ( Limulus polyphemus) is a marine Chelicerate Arthropod. Sea urchins are small globular spiny sea cat animals composing most of class Echinoidea.
Despite this variety of shells, it is quite often the case that only the shells of marine molluscs, (spelled "mollusks" in the USA), are meant when the word seashells is used. Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000
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Mollusc shells
The majority of shell-forming molluscs belong to two classes: Gastropoda (univalves, or snails) and Bivalvia (bivalves or clams, oysters, scallops, etc). The gastropod shell is a shell which is part of the body of a gastropod or Snail. The bivalve shell is one kind of Seashell, and in life it is composed of two parts two valves The tusk shells or scaphopods are a class of marine Mollusks which vary in size from very small to medium sized A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. The class Gastropoda or the gastropods, also previously known as gasteropods, or univalves, and more commonly known as Snails Bivalves are Molluscs belonging to the class Bivalvia. They have two-part shells and typically both valves are symmetrical along the hinge line There are, in addition, three other classes of mollusks which routinely create a shell, and those are: Scaphopoda (tusk shells), Polyplacophora (chitons, which have eight articulating shelly plates), and Monoplacophora (single-shelled chiton-like animals which live in very deep water, and which superficially resemble minute limpets. The tusk shells or scaphopods are a class of marine Mollusks which vary in size from very small to medium sized Chitons are small to large primitive marine Mollusks in the class Polyplacophora. Monoplacophora, meaning “bearing one plate” is a class of shelled Mollusks These organisms were known only from the Fossil record ranging from the
Nautiluses are the only extant cephalopods which have an external shell, although octopuses, cuttlefish and squid (especially Spirula spirula), have small internal shells. The Palau Nautilus ( Nautilus belauensis) is a species of Nautilus native to the waters around the Pacific Island nation of Palau Nautilus (from Greek ναυτίλος, 'sailor' is the common name of any marine creatures of the Cephalopod family Nautilidae, the sole The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by The Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class (which also includes Squid, Octopuses Squid are marine Cephalopods of the order Teuthida, which comprises around 300 species Spirula spirula is a Species of deepwater Squid -like Cephalopod. Females of the octopus genus Argonauta secrete a specialised paper-thin eggcase in which they partially reside, and this is popularly regarded as a shell, although it is not attached to the body of the animal. The argonauts ( Genus Argonauta, the only extant genus in the Argonautidae family are a group of Pelagic Octopuses
Malacology, the scientific study of molluscs as living organisms, has a branch devoted to shells, called conchology - although it should be noted that these terms used to be, and to a minor extent still are, used interchangeably, even by scientists (this is more common in Europe). Malacology is the branch of Invertebrate Zoology which deals with the study of Mollusks the second-largest Phylum of animals in terms of described Conchology is the scientific, semi-scientific or Amateur study of mollusk shells (in the UK spelled mollusc shells
Creating the shell
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. In Japanese cuisine, Geoduck (mirugai is sometimes referred to as "giant clam" The mantle is an important part of the anatomy of Molluscs It is the dorsal body wall which covers the visceral mass 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.
Composition of mollusc shells
Shells are composite materials of calcium carbonate, found either as calcite or aragonite and organic macromolecules, mainly proteins and polysaccharides. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Aragonite is a Carbonate mineral, one of the two common naturally occurring polymorphs of Calcium carbonate, Ca[[carbon C]] O 3 Shells can have numerous ultrastructural motifs, the most common being crossed-lamellar (aragonite), prismatic (aragonite or calcite), homogeneous (aragonite), foliated (aragonite) and nacre (aragonite). Nacre, also known as mother of pearl, is an organic-inorganic Composite material produced by some Mollusks as an inner shell layer Although not the most common, the nacre is the most studied layer. Shells of the class Polyplacophora are made of aragonite
Mollusc shells (especially those formed by marine species) are very durable and outlast the otherwise soft-bodied animals that produce them by a very long time (sometimes thousands of years). Chitons are small to large primitive marine Mollusks in the class Polyplacophora. Aragonite is a Carbonate mineral, one of the two common naturally occurring polymorphs of Calcium carbonate, Ca[[carbon C]] O 3 They fossilize easily, and fossil mollusc shells date all the way back to the Cambrian period. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with Large amounts of shells sometimes form sediment, and over geological time spans can become compressed into limestone deposits. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3
Mother of pearl and pearl formation
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. Nacre, also known as mother of pearl, is an organic-inorganic Composite material produced by some Mollusks as an inner shell layer 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. In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body The ectoderm is the start of a tissue that covers the body surfaces Mollusk blood is rich in dissolved calcium, and during shell deposition, the calcium is concentrated out from the blood and crystallized as calcium carbonate. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells such as nutrients and oxygen—and transports Waste products Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 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. Parasitism is a type of symbiotic relationship between Organisms of different Species. In Biology, detritus is non-living particulate organic material (as opposed to dissolved organic material
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. Parasitism is a type of symbiotic relationship between Organisms of different Species. This process eventually forms what we call pearls and continues for as long as the mollusk lives. A pearl is a hard roundish object produced within the soft tissue (specifically the mantle) of a living shelled Mollusk. 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. Pinctada is a Genus of pearl oysters. These are saltwater clams marine Bivalve Molluscs of the Genus Pinctada
Non-marine mollusks
In fresh water shell-bearing mollusks are represented by families from the orders Unionoida (freshwater mussels) and Veneroida (clams), as well as the class Gastropoda (snails). The white-lipped snail ( Cepaea hortensis) is a medium-sized Species of air-breathing land Snail, a terrestrial Pulmonate The Pulmonata or "pulmonates" are an order (once a Subclass) of Snails and Slugs that have developed a pallial Lung Freshwater is a word that refers to bodies of water such as Ponds lakes rivers and streams containing low concentrations of dissolved Salts and other Total dissolved Unionoida is an order within the class Bivalvia. Members of the order Unionoida which includes the pearly freshwater Mussels are found on six continents The Veneroida or veneroids are an order of Bivalve Molluscs They include some familiar forms such as saltwater Clams and The class Gastropoda or the gastropods, also previously known as gasteropods, or univalves, and more commonly known as Snails The word snail is a Common name that can be used for almost all members of the Molluscan class Gastropoda which have coiled shells in the
The class Gastropoda also includes many land snails, most of which are pulmonates and breathe air. Although the great majority of land snails are small and inconspicuous, the large and highly-colored shells of some tropical species are prized by collectors. In certain tropical islands such as Cuba, or Papua New Guinea, there are almost as many species of land snails as there are of marine. Land snails cannot disperse very easily, so populations frequently become isolated from each other, resulting in situations where adjacent islands, or even adjacent valleys separated by hills or mountains, contain closely-related but clearly separate species of land snails.
Seashell collecting as a hobby
Both the science of studying mollusk shells and the hobby of collecting and classifying them are known as conchology -- the line between professional and amateur enthusiasts is often quite blurry. Conchology is the scientific, semi-scientific or Amateur study of mollusk shells (in the UK spelled mollusc shells
Shells of marine molluscs (some of which wash up on beaches or live in the intertidal or sub-tidal zones and are therefore easily found without specialized equipment) are collected by a large number of enthusiasts. Many shell collectors find their own material or are interested in "specimen shells": shells in good condition which come with full scientific collecting data: information including how, when, where, in what habitat, and by whom, they were collected.
In the tropical and sub-tropical areas of the planet, there are far more species of colorful, large, and intertidally-dwelling seashells than there are in the temperate zones and the regions closer to the poles.
Other sea creatures
The brachiopods, or lamp shells, superficially resemble clams, but the phylum is completely unrelated to molluscs. The double spined urchin or banded sea urchin, Echinothrix calamaris, is a urchin, with a test (shell diameter of about 5 cm. Mictyris is a Genus of brightly coloured Crabs placed in its own taxonomical family, the Mictyridae. Diatoms ( Greek: (dia = "through" + (temnein = "to cut" i Brachiopods (from Latin brachium, arm + New Latin -poda, foot are a small phylum of Benthic Invertebrates Also Most lines of brachiopods were ended during the Permian-Triassic extinction event, and their ecological niche filled by bivalves. The Permian–Triassic (P–Tr extinction event, informally known as the Great Dying, was an Extinction event that occurred, and 70 percent of terrestrial
The construction of the shell-like structures of corals are aided by a symbiotic relationship with a class of algae, zooxanthellae. Corals are Marine organisms from the class Anthozoa and exist as small Sea anemone –like Polyps typically in colonies of many This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Zooxanthellae (plural ˌzoʊoʊzænˈθɛli are golden-brown intracellular Endosymbionts of various marine Animals and Protozoa, especially Anthozoans Typically a coral polyp will harbour particular species of algae, which will photosynthesise and thereby provide energy for the coral and aid in calcification,[1] while living in a safe environment and using the carbon dioxide and nitrogenous waste produced by the polyp. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Coral bleaching is a disruption of the balance between polyps and algae, and can lead to the breakdown and death of coral reefs. Coral bleaching is the loss of color of Corals due to stress-induced expulsion of symbiotic Unicellular Algae or due to the loss of pigmentation within
Some echinoderms (starfish, sea urchins, sand dollars) and some polychaetes (annelid worms) also have hard exoskeletons. Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) Starfish (also called sea stars) are any Echinoderms belonging to the class Asteroidea. Sea urchins are small globular spiny sea cat animals composing most of class Echinoidea. Sand dollars (order Clypeasteroida are flat round marine animals related to sea urchins ( Echinoids, sea stars and other echinoderms The Polychaeta or polychaetes are a class of Annelid worms generally marine The now-extinct ostracoderms ("shell-skins") were a type of armoured marine fish which flourished in North America and Europe during the Ordovician, Silurian and Devonian geological periods. Ostracoderms ("shell-skinned" are any of several groups of extinct, primitive jawless Fishes that were covered in an armor of bony plates The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 The Silurian is a geologic period and system that extends from the end of the Ordovician period about 443 The Devonian is a geologic period and system of the Paleozoic era spanning from to million years ago.
Arthropods
Many arthropods have sclerites, or hardened body parts, which form a stiff exoskeleton made up mostly of chitin. Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " A sclerite ( Greek skleros meaning " hard " is a hardened body part Chitin ( C 8 H 13 O 5 N)n (ˈkaɪtən is a long-chain Polymer of a N-acetylglucosamine In crustaceans, especially those of the class Malacostraca (crabs, shrimp and lobsters, for instance), the plates of the exoskeleton may be fused to form a more or less rigid carapace. Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting The Malacostraca (Greek "soft shell" are the largest class of Crustaceans and include most of the animals that non-experts recognize as crustaceans including A carapace is a dorsal section of an Exoskeleton or shell in a number of animal groups
Chelonians
Sea turtles also form a carapace and plastron of bone and cartilage which is developed from their ribs. Sea turtles ( Superfamily Chelonioidea) are Turtles found in all the world's oceans except the Arctic Ocean. A carapace is a dorsal section of an Exoskeleton or shell in a number of animal groups The plastron is the nearly flat part of the shell structure of a Turtle or Tortoise, what one would call the belly similar in composition to the Carapace Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce Cartilage is a type of dense Connective tissue. It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix In Vertebrate Anatomy, ribs ( Latin costae) are the long curved Bones which form the ribcage.
Planktons and protists
Plant-like diatoms and animal-like radiolarians are two forms of plankton which form hard silicate shells. Diatoms ( Greek: (dia = "through" + (temnein = "to cut" i Radiolarians (also radiolaria) are Amoeboid Protozoa that produce intricate Mineral Skeletons typically with a central capsule Plankton consist of any drifting Organisms ( Animals Plants Archaea, or Bacteria) that inhabit the Pelagic zone of The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide
Foraminifera and coccolithophore create shells called "tests" of calcium carbonate. The Foraminifera, ("Hole Bearers" or forams for short are a large group of Amoeboid Protists with reticulating Pseudopods fine Coccolithophores (also called coccolithophorids) are single-celled Algae, Protists and Phytoplankton belonging to the Division
Shells as decorative items in human culture
Throughout the history of humanity, shells of many types and from many different kinds of animals have been popular as human adornments. They are often used whole and drilled so that they can be threaded like a bead, or cut into pieces of various shapes.
The uses have included all kinds of pendants, beads, buttons, brooches, rings, and hair combs among other uses. A bead is a small decorative object that is pierced for threading or stringing In Clothing and Fashion design, a button is a small plastic or metal disc- or knob-shaped typically round object usually attached to an article of Clothing A brooch (also known in ancient times as a fibula, and not to be confused with broach) is a Decorative jewelry item designed to be attached to A finger ring is a band worn as a type of ornamental Jewellery around a finger it is the most common current meaning of the word ring. A comb is a device made of solid material generally flat always toothed and is used in hair care for straightening and cleaning hair or other fibers
The Moche culture of ancient Peru worshipped animals and the sea and often depicted shells in their art. The Moche civilization (alternately the Mochica culture Early Chimu Pre-Chimu Proto-Chimu etc Peru (Perú Piruw Piruw officially the Republic of Peru ( reˈpuβlika del peˈɾu is a country in western South America. [2] Native American used shells for wampum and hair pipes. For indigenous peoples in the United States other than Hawaii and Alaska see also Native Americans in the United States. Wampum is a string of creamy white colored shell beads fashioned from the North Atlantic Channeled whelk ( Busycotypus canaliculatus) shell and is traditionally used A Hair Pipe is a term for a long narrow Bead, more than 15 inches long which were popular with American Indians. [3]
Small pieces of colored and iridescent shell have been used to create mosaics and inlays which have been used to decorate larger items such as boxes and furniture. Art History Mosaics of the 4th century BC are found in the Macedonian palace-city of Aegae, and they enriched the floors of Hellenistic Inlay is a decorative technique of inserting pieces of coloured materials into depressions in a base object to form patterns or pictures Large numbers of whole seashells, arranged to form patterns, have been used to decorate man-made grottos. A grotto (Italian grotta) is any type of natural or artificial Cave that is associated with modern historic or prehistoric use by humans
See also
- The Bailey-Matthews Shell Museum
- Seashell surface, a mathematical construct
References
- ^ Madl, P. The Bailey-Matthews Shell Museum is a museum of Seashells and Conchology located in the city of Sanibel Florida on Sanibel Island on the In mathematics a seashell surface is a surface made by a circle which spirals up the z -axis while decreasing its own radius and distance from the z -axis and Yip, M. (2000). Field Excursion to Milne Bay Province - Papua New Guinea. Retrieved on 2006-03-31. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 307 - After divorcing his wife Minervina, Constantine marries Fausta, the daughter of the retired Roman Emperor
- ^ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. The Larco Museum (Museo Larco is located in the Pueblo Libre District in Lima, Peru. New York: Thames and Hudson, 1997. Thames & Hudson (also Thames and Hudson and sometimes T&H for brevity are a Publisher, especially of Art and Illustrated Books
- ^ Shell Hair Pipes used in Indian Adornment
External links
Dictionary
seashell
-noun
-adjective
- (color) of a very light pink colour, like that of some seashell.
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