Conchyliologie

Conchology () is the study of mollusc shells. Conchology is one aspect of malacology, the study of molluscs; however, malacology is the study of molluscs as whole organisms, whereas conchology is confined to the study of their shells. It includes the study of land and freshwater mollusc shells as well as seashells and extends to the study of a gastropod's operculum. Conchology is now sometimes seen as an archaic study, because relying on only one aspect of an organism's morphology can be misleading. However, a shell often gives at least some insight into molluscan taxonomy, and historically the shell was often the only part of exotic species that was available for study. Even in current museum collections it is common for the dry material (shells) to greatly exceed the amount of material that is preserved whole in alcohol. Conchologists mainly deal with four molluscan orders: the gastropods (snails), bivalves (clams), Polyplacophora (chitons) and Scaphopoda (tusk shells). Cephalopods only have small internal shells, with the exception of the Nautiloidea. Some groups, such as the sea slug nudibranchs, have lost their shells altogether, while in others it has been replaced by a protein support structure. The terms shell collector and conchologist can be regarded as two distinct categories. Not all shell collectors are conchologists; some are primarily concerned with the aesthetic value of shells instead of their scientific study. It is also true that not all conchologists are shell collectors; this type of research only requires access to private or institutional shell collections. There is some debate in the conchological community, with some people regarding all shell collectors (regardless of motivation) as conchologists. Shell collecting, the precursor of conchology, dates back thousands of years. Archaeologists have sometimes uncovered Stone Age oceanic seashell necklaces in areas far from the ocean, indicating that they were traded, and shell jewellery has been found at archaeological sites around the world.

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Coquille (mollusque)

Une coquille est le squelette externe d'un mollusque. La majorité des mollusques à coquille se trouve dans la classe des gastéropodes comme les escargots, et dans celle des bivalves comme les huîtres. Trois autres classes de mollusques sécrètent systématiquement une coquille : les scaphopodes (dentales), les polyplacophores (ou chitons) et les monoplacophoress. C'est aussi le cas pour la quasi-totalité des céphalopodes, même si elle est parfois réduite et recouverte par le manteau (« os » des seiches ou « plume » des calmars).

Seashell

A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washed up on beaches by beachcombers. The shells are empty because the animal has died and the soft parts have decomposed or been eaten by another animal. A seashell is usually the exoskeleton of an invertebrate (an animal without a backbone), and is typically composed of calcium carbonate or chitin.

Malacologie

La malacologie (du grec ancien , « mou ») est la branche de la zoologie consacrée à l'étude des mollusques. Une subdivision de la malacologie, la conchyliologie, est consacrée à l'étude des mollusques à coquille. Une autre, la teuthologie, est consacrée à l'étude des céphalopodes. Cette discipline est souvent divisée en malacologie continentale et marine. Sur les continents les mollusques aquatiques constituent à eux seuls un champ d'étude particulier.

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