pearl culture presentation
                     Pearl culture
Submitted by
Jyoti pal
1892547
Fish Biology
M.Sc. Zoology (final year)
Introduction
Pearls are unique as the only gems produced by a living organism.
These structures are secreted by the mantle (i.e., the skin) of pearl oysters in response to irritations caused by stimuli such as sand grains, molluscs eggs, 
parasites, detritus, and other foreign particles.
History
China is the principal nation which delivered artificial pearl in the 13th century creating the old style Buddha pictures in the freshwater mussel in lake 
Tahu in central china.
 Japan built up the modern pearl culture and furthermore consummated the strategies of pearl culture in marine pearl oyster in the prior part of present 
century. 
India's potential for culture with its asset of P.fucata and innovative achievement came about just in 1973 of every an experimental project of the Central 
Marine Fisheries Research Institute (CMFRI) based at Tuticorin.
Pearl culture in India
India has probably the most appeal for pearls for setting in gems. The pearl oyster fisheries are situated in two principle regions:
1) The Gulf of Mannar of Tuticorin coast   
2) The Gulf of Kutch on the northwest coast 
                                                                                                                                                         
Morphology and Anatomy of pearl oyster
Morphology
Structure of shell
Shell of pearl oyster made up of three layers :
 Outermost layer is consist of organic conchiolin layer or periostracum.
 Middle layer prismatic layer is consist of numerous layers of calcite crystals of calcium carbonate.
 Innermost Nacreous layer is consist of small irregular , roundish or polygonally formed cover of 
aragonite crystals.
  
                                                        Transverse section of shell C.L-Conchiolin layer, P.L-Prismatic layer, N.L-Nacreous layer 
Anatomy
The delicate body of the pearl oyster comprises of a couple of mantle lobes, visceral mass, gills, foot, 
posterior adductor muscle and other musculature.
Mantle
  It follows in the form of the valves (shells) wraps the various delicate pieces of the body. 
 The right and left lobes join dorsally beneath the hinge line.
 The mantle lobe can be separated into three regions:
 The Marginal mantle with folds.
 The pallial mantle quickly inside the folds.
 The central mantle which forms the bigger zone of the lobe.
      Visceral mass
 The visceral mass comprises of the organs worried about feeding and digestion, reproduction, blood circulation and excretion.
 The sexes are isolated with no external differences.
  The Reproductive system comprises of a couple of gonads which, when in mature state, spreads superficially over the 
hepatopancreas and intestine.
                                                                                Silver lip pearl oyster 
Pearl oyster farming
Selection of culture site
Environmental Conditions
Temperature :  (20 – 25 °C)                                                                
Salinity : (above 30 ppt)
Bottom :   (Gravelly)                                                                           
Depth :    (Optimum depth at ~ 15m )
Silt load  : prefer clear water as high turbidity                                    
Water flow : Moderate water currents
Primary productivity :  Good phytoplankton production
Supply of oyster
Rearing method                   (A) Culture raft constructed with teak poles; (B) A FRP styrofoam buoy; (C) A mild steel buoy, and (D) Oyster long-line 
culture system                                                            
Raft culture
Long line culture
On bottom culture
 Rearing containers
Culture of Mother Oyster in Box cages
juvenile pearl oyster are reared in  frame net cages 
                                                (A) A box-cage containing pearl oysters and (B) A frame netcage with oysters 
Organism which harm the oyster
Serious issues in pearl oyster farming are brought about by biofouling organisms which settle and 
develop on the oyster shells.
By boring organisms which perforate through the shells making them weak and friable. 
By predators which feed on the oyster. 
Control measures
For controlling fouling development is by cleaning the oyster, cages.
The boring polychaetes are simply killed by submerge the oyster in freshwater for around 6 hours.
Oyster spat can be furthermore shielded from fish by covering the rearing cages with old fish net. 
                                                                                                                    
Surgery in pearl oyster
In culture pearl creation, a mantle piece from the giver oyster is grafted into the gonad of the recipient oyster, alongside a 
circular nucleus to give the two expected conditions to the formation of pearl. The operation on the pearl oyster is done by a 
skillful surgery. 
Surgical tools which are used in surgery is oyster knife, clamp, speculum, graft knife, incising-cum-grafting needle, nucleus 
implanting needle, needle hook, spatula and scalpel. 
Selection of oysters for operation
age: above 1.5-2 years
Weight > 25 g (40 mm) 
Stage of maturity spent resting stage 
Overall health: Good, free from infections 
Preparation of graft tissue:                                                                            Steps for graft tissue preparation
Little pieces cut from the pallial mantle region are utilized as graft tissues for transplantation. 
2-3 mm square mantel pieces are prepared.  
Condition for surgery
 Narcotization of selected oysters by sprinkling  menthol in the sea water.                                        
                                                   
Implantation of Nucleus and Mantle tissue
Nucleus
 6–7 mm, are commonly utilized in single implantation, one nucleus in each oyster 
 4–6 mm are utilized for double implantation
 Nucleus with distances across of 2–3 mm are commonly utilized in multiple implantations, at least five nucleus in a single oyster.
 The perfect site for nucleus implantation is the gonad, especially in its ventral segment. Single implantation is constantly done at 
this site.
  In double implantation, the above site is utilized for the bigger nucleus while a site in the dorsal area of the gonad, near the 
hepato-pancreas, is utilized for the littler nucleus.
 
Post operative care
 Implanted oysters are placed in cages. 
  Healing of operated tissue takes about 3-4 days. 
 Dead oysters are removed. 
  Healthy implanted oysters are transferred to culture cages and suspended at depth of about 2-3 m.
Formation of pearl
 The pearl is formed by a similar procedure as the shell of the pearl oyster because of 
secretion of the mantle tissue. The external epithelial layer of mantle is liable for the 
discharge of the nacreous layers of which the pearl is made out of. The external epithelial 
cells of the mantle may fall unintentionally into the body of the pearl oyster, recovering a 
sac comprising of a solitary layer of cells, the purported pearl-sac, inside which a 
characteristic pearl develops because of the secretion of nacre.
 The formation of natural pearl is affected by foreign bodies incidentally entering the body 
of the oyster. The foreign bodies may get caught between the shell and the mantle. Under 
the upgrade of the foreign body, the external epithelium of the mantle invaginates and 
shapes a pearl-sac and formation of blister pearl or a free pearl inside the mantle. Each 
characteristic pearl has an internal center or nucleus.
 In the cultured pearl technique, the process is manipulated in the pearl oyster. A small 
piece of mantle from a donor oyster is grafted into the gonad of the recipient oyster 
together with a nucleus by a skillful surgery. The outer epithelium of the mantle piece 
regenerates itself around the nucleus to form a pearl-sac which faithfully secretes and 
Process of pearl formation. (A) Round 
deposits nacre or mother-of-pearl on the nucleus, eventually resulting in a pearl. Since this and half-natural pearls; (B) half-
pearl is produced in the oyster by manipulation at surgery and by further cultivation of the cultured pearl; and (C) round cultured 
seeded oyster, it is called the cultured pearl.The half pearls are produced by fixing the pearl with an artificially implanted 
nucleus 
nuclei on the nacreous face of the shell at appropriate sites.                                          
                                                                                                                                                    
Production of cultured pearl
 Net production is the no. of produced cultured pearls by the survived oyster in the farm. In one implantation, rate of 
production accomplished is around 65 %.
  Grade A pearls would comprise of round, shiny pearls of pink, silver or light cream shading with no defect or with 
extremely minor blemishes, for example, a little dimple or with a bulge of the size of the tip of a pin.
 Grade B would comprise of round, radiant pearls of comparable shading as grade A' with the imperfections somewhat 
more articulated yet which can be treated at preparing to make them unclear from Grade-A pearls.
 Grade C has those with more imperfections, stains or anomalies fit as a fiddle, for example, baroques. Grade D, would 
contain all the not properly formed and gravely covered ones. 
 The initial three grades should together records for around 60 % of the gross production. The rest 40% (Grade-D) would 
nearly be rejects. 
 Harvesting of pearl or beaching is finished during times of low temperature and pH. Collection of pearl is done either with 
the assistance of machines or by hand. At the point when re-utilization of oyster for a second yield of pearls is wanted, and 
is conceivable, the pearls alone are painstakingly expelled by opening the pearl-sacs through the gonad and oysters are 
come back to the homestead to anticipate their chance for medical procedure a subsequent time. 
      Thank you