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Perle
Les perles sont de petites billes, generalement de couleur blanche, créées par certains mollusques, principalement les huîtres. Quand un objet irritant passe à l'intérieur de la coquille, l'animal réagit en entourant l'objet d'une couche de carbonate de calcium CaCO3 sous la forme d'aragonite ou de calcite. Ce mélange est appelé nacre.
Autrefois uniquement obtenues par le hasard, les perles font aujourd'hui l'objet d'une culture (perliculture). Elle a été mise au point par les Japonais du début du XXe siècle aux années 1970. Depuis, le secret de leur technique s'est répandu dans tout les archipels de l'océan Pacifique, et la Polynésie française est le principal producteur. Biochimie
La nacre est un carbonate de calcium cristallisé sous forme orthorombique (maille parallélépipédique) formant des cristaux d'aragonite. Ces cristaux se forment sur un substrat de protéines et de sucres complexes qui lui confére une grande solidité. Il s'agit, de fait, d'une bio-minéralisation, qui peut servir de mécanisme de défense vis-à-vis de l'intrusion d'un corps étranger[1].
La qualité esthétique de la perle dépend de l'épaisseur de la nacre (plus importante lorsque la perle est naturelle) mais aussi de la régularité de la cristallisation. Sa coloration est probablement multifactorielle (race de l'huitre mais également, nutrition de cette dernière).
Le vin est une boisson alcoolisée obtenue par la fermentation du raisin, fruit de la vigne (Vitis vinifera).
En Europe, selon la définition légale, le vin est le produit obtenu exclusivement par la fermentation alcoolique, totale ou partielle, de raisins frais, foulés ou non, ou de moûts de raisins[1].
La transformation du raisin en vin est appelée la vinification. L'étude du vin est l'œnologie (du grec œno = vin et logie = science).
Le secteur viticole se sépare en deux professions : les vignerons indépendants (représentés en France par les Vignerons Indépendants de France) qui assurent la production de leur vin, du cep de vigne à la mise en bouteille, en passant par la vinification et qui constitue la branche artisanale, et les vignerons coopérateurs qui n'effectuent pas la vinification.
The term "fish" is most precisely used to describe any non-tetrapod chordate, i.e., an animal with a backbone that has gills throughout life and has limbs, if any, in the shape of fins.[1] Unlike groupings such as birds or mammals, fish are not a single clade but a paraphyletic collection of taxa, including hagfishes, lampreys, sharks and rays, ray-finned fishes, coelacanths, and lungfishes.[2][3]
A typical fish is cold-blooded; has a streamlined body that allows it to swim rapidly; extracts oxygen from the water using gills or an accessory breathing organ to enable it to breath atmospheric oxygen; has two sets of paired fins, usually one or two (rarely three) dorsal fins, an anal fin, and a tail fin; has jaws; has skin that is usually covered with scales; and lays eggs that are fertilized internally or externally.
Fish come in many shapes and sizes. This is a sea dragon, a close relative of the seahorse. Their leaf-like appendages enable them to blend in with floating seaweed
To each of these there are exceptions. Tuna, Swordfish, and some species of sharks show some warm-blooded adaptations, and are able to raise their body temperature significantly above that of the ambient water surrounding them.[4] Streamlining and swimming performance varies from highly streamlined and rapid swimmers which are able to reach 10-20 body-lengths per second (such as tuna, salmon, and jacks) through to slow but more maneuverable species such as eels and rays that reach no more than 0.5 body-lengths per second.[5] Many groups of freshwater fish extract oxygen from the air as well as from the water using a variety of different structures. Lungfish have paired lungs similar to those of tetrapods, gouramis have a structure called the labyrinth organ that performs a similar function, while many catfish, such as Corydoras extract oxygen via the intestine or stomach.[6] Body shape and the arrangement of the fins is highly variable, covering such seemingly un-fishlike forms as seahorses, pufferfish, anglerfish, and gulpers. Similarly, the surface of the skin may be naked (as in moray eels), or covered with scales of a variety of different types usually defined as placoid (typical of sharks and rays), cosmoid (fossil lungfishes and coelacanths), ganoid (various fossil fishes but also living gars and bichirs, cycloid, and ctenoid (these last two are found on most bony fish.[7] There are even fishes that spend most of their time out of water. Mudskippers feed and interact with one another on mudflats and are only underwater when hiding in their burrows.[8] The catfish Phreatobius cisternarum lives in underground, phreatic habitats, and a relative lives in waterlogged leaf litter.[9][10]
Fish range in size from the 16 m (51 ft) whale shark to the 8 mm (just over ¼ of an inch) long stout infantfish.Many types of aquatic animals commonly referred to as "fish" are not fish in the sense given above; examples include shellfish, cuttlefish, starfish, crayfish and jellyfish. In earlier times, even biologists did not make a distinction - sixteenth century natural historians classified also seals, whales, amphibians, crocodiles, even hippopotamuses, as well as a host of aquatic invertebrates, as fish[11]. In some contexts, especially in aquaculture, the true fish are referred to finfish to distinguish them from these other animals.
