Here is a compilation of essays on ‘Pearl Culture’ for class 11 and 12. Find paragraphs, long and short essays on ‘Pearl Culture’ especially written for school and college students.
Essay on Pearl Culture
Essay Contents:
- Essay on the Introduction to Pearl Culture
- Essay on the Pearl Formation Process
- Essay on the Composition and Quality of Pearl
- Essay on the Pearl Production Process and Its Industry
- Essay on the Problems and Suggestions for Pearl Industry
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Essay # 1. Introduction to Pearl Culture:
Pearls have always been a source of attraction for ladies and gents. People of all age group and all the profession have the same attraction for pearls. Pearls have been a rare and one of the most valuable objects for people and they are supposed to be done of the best and most loving thing for people of all ranks either rich, poor or of medium economic status.
The proverb “Soft and flawless like a pearl” itself is sufficient to explain the character and quality of a pearl as well as its rank in a society. They have always attracted businessmen, doctors and kings for their price medicinal value and luster. It ranks high amongst the animal products.
Pearl is produced by a special kind of Mollusca commonly known as “Pearl oyster”. It is a small bivalve shelled animal living in seawater, they are found in undisturbed areas of the sea, away from the coasts at a depth of 10-15 fathoms.
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All the pearl oysters are not able to form pearl; its rare occurrence is due to its mode of formation. It is known to Chinese since 2300 B.C. but remained in closed-door practice. For Indian Vaidhyas it was known for its medicinal value and is termed as “Mukta” or “Moti”.
It is a small about 100 mm diameter, rounded, flawlessly white, coloured, pinkish, yellowish or bluish coloured calcareous product. In most of the cases the outer structure may be rounded but in general reshaped, oblong and distorted pearls are also founded.
Rounded pearls are supposed to be the best. The nucleus of the pearl may contain a foreign object of different nature otherwise it is a simple deposition of calcium carbonate. The iridescent luster its shooting effect makes it precious. The quality of pearl and its cost depends upon the nucleus of the pearl and its luster along with the shape and size.
Essay # 2. Pearl Formation Process:
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Pearl formation is a rare and accidental phenomenon, which takes about 2-6 years for attaining a good diameter. The longer time the bigger would be the size of the pearl but the pearl which develops within span of 3-4 years are very good in luster where as those which develop for 6 years or more loose their luster. This is due to the excess deposition of calcium carbonate, which is deposited in concentric rings. The pearls cannot be produced in all the oceans.
They are found in the warmer parts of the world and inhibit the warm water oceans. They are more common in Indian, ocean, coast of China, Japan and Pakistan. Japan is the most advanced country as far as pearl production is concerned.
But India too is one of the first few nations which are pioneer in production of pearl. In India it is found in Gulf of Kutch, Mannar, Bay of Bengal, Kanyakumari, Rameshwaram and at various other centres. Pak bay, Cyclone, Bangladesh and other coastal countries to produce pearl on small scale.
Pearl is produced by bivalve mollusc belonging to class Bivalvia, Family- Pteriidae and genus Pinctada. Some of the selected species are able to produce pearl and they are P. vulgaris, P.chemnitzi, P- margaritifera, P. anomiodes and P. atropurpurea. These are commonly known as Pearl-oysters. Besides this few other marine mollucans are able to produce pearl but their product is of inferior grade and does not have economic value.
These species are Haliotes (Linn.) mytelus, Placuna blanceta and Margratifera erythroseusis. Not only the marine bivalves but some of the fresh water bivalves too are able to produce pearl e.g., Unio and anodonta species but hey are of low grade and have no luster and economic value. Species of P. maxima and P. margaritifera are bigger in size and much healthier so they produce pearl of bigger size and best luster.
Size of a pearl depends upon the size of foreign particle, health and age of the oyster and condition of the seawater. A smaller nucleus requires more deposition as compared with a bigger nucleus. In the same way the shape of the foreign particle also is responsible for the shape of the pearl.
A healthy oyster will produce more calcium carbonate as compared with the weak and young oyster. At the same time the temperature of the water current activates the oyster. In oceans where temperature of water varies periodically the development of pearl oyster is affected and this badly affects the formation of pearl.
Formation of pearl is an interesting phenomenon. It is a protective device against the foreign invaders. It is just a chance that some of the unwanted material likes sand particle, seaweeds, crustacean larvae or any other parasite or object reaches in between the shell and the wall of the maritle.
This area is without any extra device and is unable to expel the object. In general practice the outer margin of the maritle is always attached along all sides with the nacre of the shell and no particle is allowed to invade it. But in case an object reaches this area it starts developing as a pearl.
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The composition of a pearl and shell is almost the same. The wall of the maritle on its outer peripheral zone secretes a substance, which is deposited on the margin of the shell, and the shell grows in size but the inner margin of the shell is always attached with the epithelial layer of maritle.
This layer is a secretary layer and produces calcium carbonate and conchyolin spreaded uniformly alternating with each other. This gives a white, soothing, luster to the inner layer of the shell. This is termed as “mother of the pearl” also.
The same technique is applied in the formation of pearl also. The moment an object reaches in between the above said area it creates a pressure on the maritle wall and causes irritation.
This activates the nacre secreting cells of the maritle and the secretion is deposited around the object which is termed now as nucleus. The continuous growth of the nucleus causes more and more irritation and higher glandular discharge. This causes regular growth of the nucleus and thus a pearl is formed in nature.
Essay # 3. Composition and Quality of Pearl:
Pearl comprises of water, organic matter, calcium carbonate and the residue:
(1) Water- 2.4%
(2) Organic matter- 3.5-5.9%
(3) Calcium carbonate- 90%
(4) Residue- 0.1-0.8%
Quality of Pearls:
The pearls obtained are of variable shapes and sizes. They may be white or cream red or pink red in colour. The spherical pearls of rainbow colour are rarely found. The best quality of pearl is known as ‘Lingha pearl’ and obtained from marine oysters. Pearl obtained from freshwater bivalves are not as valuable as those obtained from the marine oysters.
Artificial Pearls:
Keeping in mind the high demand and the cost of the pearl, European people have developed a new technology to form the pearl. This pearl is an artificial structure, which is formed by using the by-products of fishing industry. The scales of a cyprinid fish Alburnus species which are commonly known as Bleaks are scraped and the silvery white substance is collected and polished on the inner side of specially prepared hollow glass bead.
This produces a silvery white luster to the glass bead and this artificially coloured bead is sold as pearl. The central hollow space is filled with wax which provides strength and weight to the bead. The fish is confined to the north of Pyrenees and Alps in Europe so, such artificial pearls are common in European countries.
Essay # 4. Pearl Production Process and Its Industry:
Although pearl industry may be established only on natural basis of pearl formed by oysters in the natural conditions but an artificial device to insert the nucleus as foreign particle in the shell of oyster has proved useful for the production of pearls in greater number.
This whole process is very much complicated, technical and time taking and can be managed as given below:
Collection of Oysters:
The oysters are collected from the bottom sea by the divers particularly women divers in Japan who are called as ‘AMA’ which in Japan means ‘the girls of sea.’ The divers usually have got training for proper diving into the seawater since their childhood for the search of seashells or seaweeds. The well-protected suits of cotton with cap are used at the time of diving. Each diver has a small hand net at the time of diving when she goes upto 5 metre depth. The net helps in the collection of oysters from the bottom.
The oysters collected by nets are stocked in the wooden bucket attached to the diver’s left wrist by a cord and the diver with bucket comes up on the surface of water. An experienced diver can remain under water up to about one and half minute and can collect 2 to 10 oysters per dive. The best time for diving is form the early morning to mid-day. The best period for the collection of the oysters is of two months in the summer season when the water is nearer and the sea is calm.
During diving in deep seawater the divers operate directly from the side of boat and a rope remains tightly fitted to the diver’s wrist through which the operating boatman pulls the diver out with force up to the surface after receiving any signal from the partner. Thus, the whole collected oysters are stored and stored out.
The oysters of same age group are segregated and two years old are kept in shallow water for future. Three years old oysters are sent to shallow water and in the months of April and May they are taken out. For pearl industry and proper supply of oysters, its eggs are incubated artificially which solves the problem of obtaining oysters for pearl culture.
Oysters are also caught by special type of cages (84 × 54 × 20 cm) by covering a heavy wire frame with two centimeter wire mesh. This cage is dipped into hot coltar as a measure against corrosion. Now this cage is dipped into the sand-cement mixture providing rough surface to the cages are suspend at a depth of 6 month from July to November where spots are easily available. These collected oysters are now transferred to rearing cages.
Rearing of Oysters:
The collected oysters are stocked and reared in special type of cages called as rearing cage. These cages are almost similar to those of collection cages except that they are further divided into 4 to 6 smaller chamber and lack the diagonal sub-divisions. They are also covered with metal mesh and with netting of cotton.
These cages are well protected from natural enemies of oysters like Octopus, Eel, and Devilfishes etc. The collected oysters are first cleaned and then placed into the culture cages for a period of about 10 to 20 days to recover the strain due to excessive handling and for the physiological adjustment to the shallow water conditions.
Insertion of Nucleus:
The insertion of nucleus as foreign particle is very much technical process and is of great important for pearl industry. A number of methods are devised but most practicable and efficient method is one adopted by Nishikows. In this method a piece of mantle of living oyster is cut off and inserted together with a suitable nucleus inside the living tissue of another oyster.
Following steps are taken for the insertion of nucleus:
(a) Fitness of Oyster for Operation:
The selected oysters for the insertion of nucleus should be healthy and strong enough to over-come the shocks during operation. It is suggested that if the ovary and testis of oysters are got rid of they would be more resistant to the shocks of operations for this purpose oysters are dipped into cold and warm current of water alternately which initiates them to eject their sperms and eggs in case of males and females respectively.
Before operation, oysters are kept under stress of suffocation as a result they start to open their shells and at once a bamboo peg(piece)is inserted between the gap of two shells due to which shells may not be closed again.
(b) Preparation of Graft Tissue:
The piece of tissue which is inserted inside the mantle is called as ‘Graft’ tissue. A strip of about 7 × 0.75 cm is cut from the edge of mantle of healthy oysters by sharp knife.
This piece is smoothed cleaned and washed off the adhering mucus and again wiped off by wet sponge. The border of gill piece is removed by sharp scalpel. Now this tissue is trimmed to 2 to 3 cms long narrow strip and again cut transversely into small squares according to the size of the nucleus for insertion.
These squares are kept in sea water at 22oC where they can survive for about 48 hours. The outer edges of these graft squares must be known because nacre secreting cells are found only on the outer surface of the mantle so it is essential to keep the outer surface in contact with the inserted nucleus.
(c) Preparation of Nucleus:
Although any small particle may function as nucleus to initiate the pearl formation but it is reported that calcareous nucleus is the best because the deposition of nacre was found to be more satisfactory on calcarious nucleus as compared to any other particle.
Best nucleus is formed by the shell of molluscs with heavy deposition of calcareous shells. Such type of molluscs are easily available in India but Japan depends on U.S.A. for good quality of calcarious shells. It is also not able that spherical nucleus is best for the formation of good quality of spherical pearl.
(d) Insertion of Nucleus:
For the insertion of nucleus, oysters are fixed in a desk clamp in the position of right valve facing upward. Mantle folds are smoothly touched to expose the foot and the main body mass, followed by an incision into the epithelium of the foot and a slender channel in to the main mass. Suddenly one graft tissue piece is placed into the channel and the nucleus is placed over the graft tissue which functions as a bed for the nucleus.
Now the bamboo peg is quickly removed and oyster shells are closed automatically. For the insertion of the second nucleus similar operation is performed from the left side in the gonadial tissue and third insertion should never be tried. In Japan one trained girl can operate 25 to 40 oysters per hour and these girls are called as ‘Tomarine son’ means ‘Miss Nucleus Pusher’. The operation period should not increase beyond 30 minutes and the oysters cannot survive beyond one hour of the operation period. So operation and insertion of nucleus should be performed by experienced persons.
(e) Post Operational Care:
Nucleated oysters are placed into cages and suspended into seawater and attached with floating rafts to a depth of 2 to 3 metres for about 6 to 7 days to recover from the shocks due to operation. This period of 6 to 7 days is known as ‘Recovery period. Now oysters are examined properly and dead individuals are removed from cages. Sometimes, few oysters expel out the nucleus from the body due to heavy shock.
Now-a-days it is examined by X-rays whether oysters are having inverted nucleus or not. About 3000 to 3600 nucleated oysters are kept in different cages suspended in sea water at 2 to 3 meters depth for 3 to 6 years and undisturbed except at the time of clearing and inspection. The pearl oysters grow best in warm shallow waters generally not more than 14 meter deep.
Harvesting of Pearl:
Pearl are harvested in the month of December to February which may slightly vary according to the climatic conditions of the industrial area. After the completion of 3 years of the insertion of nucleus, pearl oysters are harvested from the sea and the pearls are taken out from the shell.
Clearing of Pearls:
After taking out the pearls from the oysters shell they are washed properly, cleared with the soap solution, but pearls should not be rubbed much.
Essay # 5. Problems of Pearl Industry and Suggestions for Improvement:
Problems of Pearl Industry:
Theoretically pearl culture appears to be very much easy but practically several problems crop up during culture. Number of enemies like eel, octopus, devil fishes etc., destroys the oyster. The lethal cold water, low salinity of water, turbidity of water and high range of temperature variation hamper the pearl industry by affecting the proper rearing of the oysters.
Suggestions for Pearl Industry:
1. During pearl fishing the nets used should be of such size from, which smaller than limited sized pearl may not be caught but should pass through the net to get a chance to grow.
2. The fishing of pearl oysters should not be much so as to exhaust the stock soon.
3. During the breeding season, oysters should not be disturbed by fishing, rather allowed to breed freely. This period may be declared as close season for any fishing.