Cities do not stop growing and extending their influence; the number of inhabitants is literally mushrooming. Citizens are faced with more difficult challenges every day: How do we manage the mountains of waste they produce? How do we avoid the disastrous consequences for man and the environment?
CyberDodo and the Molluscs (1-26)
In short, one could say that Nature makes something positive of something negative! Why? Because at the origin of each pearl is a strange body that invaded the shelled mollusc (like a grain of sand). To defend itself against this invasion, the mollusc will produce layers of aragonite to seal off the intruding matter.
What is aragonite?
It is actually the same substance that mollusc shells are made of. The phenomenon known as sealing off the intruder involves the mollusc depositing layers of said substance in concentric layers which explains the round shape of the pearl!
Can all molluscs produce pearls?
Many bivalves naturally have this capacity, but given their keen and long-standing interest in pearls, man has developed a way to culture pearls, picking out three species of oyster in particular:
Who invented pearl cultivation?
Although there have been many attempts during the centuries, it was in fact the Japanese that were successful. Until the end of the 19th century, man had to rely on Nature and sheer chance in order to obtain pearls. At the turn of the century, however, Kokichi Mikimoto, Tatsuhei Mise and Tokishi Nishikawa invented pearl cultivation.
Their work allowed for an understanding of the mollusc's defence mechanism that is responsible for the creation of pearls, and also for the development of a method involving inserting a ball called a nucleus- along with a piece of membrane inside the oyster so that nacre is created - hence, upon demand a pearl is created!
The total process requires several years and the level of rejection can be significant only 10 to 20% of oysters in which seeds are sown will produce a pearl fit to be placed on the market.
At present, numerous countries, primarily in the Pacific, are pearl producers including French Polynesia, Australia, Japan and China, etc.
A celebrated pearl, among others
This pearl illustrates perfectly the interest that man has long accorded these fascinating natural creations. Found at the beginning of the 16th century in the Gulf of Panama the exceptional Peregrina pearl... first, it would be in the possession of the French Emperor Napoleon III, then the British Marquis of Abercorn, and then, in 1969 it became the property of American actress Elizabeth Taylor!
Just to dream a bit this pearl weighs around the equivalent of 200 grains that is, just around fifty carats; it is pear-shaped and is the colour white....
Are molluscs endangered?
The term mollusc refers to animals that live protected by an external shell; pearl-producing oysters are part of this family - which is actually quite huge it comprises over 100,000 species!
The branch of science that studies them is known as conchology.
As with so many other species today, many molluscs are threatened by extinction because of pollution, the disappearance of their habitat, global warming and over-harvesting, prompting the near collapse of certain regions!
Once again as well, the principle of good sense should prevail! We should ensure that future generations will be able to take advantage of the same natural resources that we inherited from our parents .
To see the cartoon on molluscs, click here
To take the quiz, click here
For the game, click here
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