WO2020160975A1

WO2020160975A1 - Process for the production of pearl from edible bivalvia and gastropoda

Info

Publication number: WO2020160975A1
Application number: PCT/EP2020/052135
Authority: WO
Inventors: Francesco Paolo PATTI; Sara FIORETTI
Original assignee: Stazione Zoologica Anton Dohrn
Priority date: 2019-02-04
Filing date: 2020-01-29
Publication date: 2020-08-13
Also published as: IT201900001577A1

Abstract

A method for the production of pearls from edible bivalvia and gastropoda is disclosed by drilling the shell in a defined position inserting a water resistant inert thermoplastic material mixed with powder of shell and closing the hole by moulding water resistant inert thermoplastic material by heating.

Description

PROCESS FOR THE PRODUCTION OF PEARL FROM EDIBLE BIVALVIA AND

GASTROPODA

Background of the invention

The present invention refers to the field of biology since it refers to a method for the production of pearls from edible bivalvia and gastropoda.

State of the Art

Several shelled molluscs in the world are industrially used to produce pearls. Oysters are the most common pearl-molluscs, particularly oysters of Pteriidae family: Pinctada fucata, Pinctada maxima , Pinctada margaritifera , Pinctada mazatlantica and Pteria penguin, (Gervis M.A. and Sims N.A. The biology and Culture of Pearl Oysters. (1992) ICLARM Stud. Rev. 21, p.49; M. Haws. The basics of pearl farming: a Layman's manual (2002) . Center for Tropical and Subtropical Acquaculture, publication n. 127; Southgate P.C. and Lucas J.S. The pearl oyster (2011) Ed. Elsevier) . Other pearl-molluscs are other bivalves molluscs like the freshwater mussel Margaritifera margaritifera , the mussels Mytilus coruscus (Chinese patent n. CN107079856) gastropods as Strombus gigas (Creswell L., Davis M. (1991) . Queen conch, the well-bred queen of the Caribbean. World Aquae. 22 (1), 28-40) and Haliotis spp . (Korean patent KR20180009761 ) .

Molluscs can produce a pearl in reaction a stress stimulus. The stress agent could be natural or human-induced, so pearls could be natural pearls or cultured pearls . In both cases the mollusc triggers a defence mechanism to isolate the foreign element, covering it with nacre layers in order to close it off. For natural pearls, their formation is generally induced by an organic material that ends accidentally up inside the animal, like a parasite or a small fragment of sponge or corals or other animals. The production of a cultured pearl is human-induced, the irritant element is a surgically implanted bead or a piece of shell, sometimes covered by mantle tissue of a donor mollusc. Pearls have fascinated man thousands of years ago and continue to do so today, they can be used above all as jewels but they can also be used in pharmaceuticals or cosmetics; their use depends on the quality. The pearls quality, both natural and human induced, depends on several factors: nacre thickness, shine, surface imperfections, shape, colour and dimension. The higher quality pearls are used in jewellery; in which since ancient times they have always been much appreciated. The lower quality pearls are not generally used in jewellery, so are pulverized in order to have very high quality of pure calcium for cosmetics or pharmaceutical use. In cosmetics, the pearls powder could be one of the main ingredient in anti-aging products; for pharmaceuticals it is an excellent source of calcium useful for dietary supplement.

From the 18th century to the beginning of the 19th century in Europe there was intensive research on pearl formation. It was in Japan, from the 19th century, that began the real pearl industry (Nagai K. (2013) . A History of the Cultured Pearl Industry. Zoological Science 30, 783-793) . The first license for pearls production dates back to 1920, by the Japanese Kokichi Mikimoto, the methods consisted of first enwrapping an artificial stimulus in a bag formed by assembling the mantle- parenchyma of a living oyster, sealing the mouth of the mantle- bag so formed with a cord, and introducing it, as a whole, into the subcutaneous tissues portion of the shell-secreting epidermis through the cut or opening surgically provided for the purpose, holding the shell open with a wedge, and introducing there through a suitable tool such as knife or spatula, carefully working along the inner surface of the shell until the ligament thereof is eventually detached therefrom, then the cord of the stimulus is taking off and disinfecting the wound in forming the said cut. To prevent a migration of the stimulus thereby retaining it firmly at rest in its place it is immediately introduced into the said subcutaneous portion of the shell-secreting epidermis of the molluscs. Besides being treated with tannin or other suitable astringent, the latter important because of the reason that the exciting action of the astringent not only positively retains the stimulus in position but at the same time expedites the coagulation of the blood and lymph. The operation requires skill and quick manipulation so that work may be completed while the molluscs is still alive. The cut or wound may be properly disinfected with iodine, ether or other suitable sterilizing substance. The oysters thus operated upon are then regularly planted back to their native water, and remain there for a certain number of years (Japanese patent 312855) . The method disclosed in JP 312855 remained very similar today, it known now as grafting or seeding operation; during the surgical operation two elements are implanted into the gonad of a recipient pearl oyster: a living tissue fragment (saibo) from the mantle of a donor pearl oyster, along with a small inorganic bead or "nucleus", generally obtained from the shell of the Mississippi freshwater mussel, (Ky C . -L . , Molinari N. , Moe E., Pommier S. (2014) . Impact of season and grafter skill on nucleus retention and pearl oyster mortality rate in Pinctada margaritifera aquaculture. Aquacult Int) . Over the years, it has been tried to improve the above grafting technique; like the use of a nucleus-inserting tool (Chinese patent n. CN107494359) or implanting surgery method capable of sending a nucleus and a piece of a mantle donor oyster simultaneously (Chinese patent n. CN107466929) . The obtained pearls could be free inside the body of the molluscs or attached to the shell. Pearls of spherical shape are most valuable ones, but there are pearls with different and non-regular shapes. Furthermore, pearls could have different colours, among the same pearl oyster species the phenotypic diversity of the donor oyster could finally influence pearl colour (Ky C.-L, Blay C., Aiho V. , Cabral P., Le Moullac G. , Lo C. (2017) Macro-geographical differences influenced by family based expression on cultured pearl grade, shape and colour in the black-lip "pearl oyster" Pinctada margaritifera: a preliminary bi-local case study in French Polynesia. Aquaculture Research 48, 270-282).

Despite the technique used is always the same during the years, research on pearl formation is still very active today. New investigations have been performed to improve the technique and to identify the best mantle donors, the best generation, the right combination of light, food, breeding condition to optimize the production and some methods to avoid the nucleus rejection and the high mortality rate (Wada and Komaru (1996) Color and weight of pearls produced by grafting the mantle tissue from a selected population for white shell color of the Japanese pearl oyster Pinctada jixata martensii (Dunker) . Aquaculture 142, 25- 32; Pouvreau S., Tiapari J. , Gangnery A., Lagarde F., Gamier M., Teissier H., Haumani G., Buestel D., Bodoy A. (2000) . Growth of the black-lip pearl oyster, Pinctada margaritifera, in suspended culture under hydrobiological conditions of Takapoto lagoon (French Polynesia) . Aquaculture 184, 133-154; Gueguen Y., Montagnani C., Joubert C., Marie B., Belliard C., Tayale A., Fievet J. , Levy P., Piquemal D., Marin F., Le Moullac G. , Ky C- L., Garen P., Lo C., Saulnier D. (2013). Recent Advances in Pearl Research - Proceedings of the International Symposium on Pearl Research, 184-194; Ky C.-L., Nakasai S., Molinari N., Devaux D. (2015) . Influence of grafter skill and season on cultured pearl shape, circles and rejects in Pinctada margaritifera aquaculture in Mangareva lagoon. Aquaculture 435, 361-370; Ky C-L., Koua M. S., Le Moullac G. (2018). Impact of spat shell colour selection in hatchery-produced Pinctada margaritifera on cultured pearl color. Aquaculture Reports 9, 62-67 , Latchere O, Mehn V, Gaertner-Mazouni N, Le Moullac G, Fievet J, Belliard C, et al. (2018) Influence of water temperature and food on the last stages of cultured pearl mineralization from the black-lip pearl oyster Pinctada margaritifera. PLoS ONE 13(3): e0193863). Furthermore, genetic and molecular investigations on pearls formation are increasing investigations (Inoue N. , Ishibashi R. , Ishikawa T., Atsumi T., Aoki H., Komaru A. (2010) . Can the Quality of Pearls from the Japanese Pearl Oyster ( Pinctada fucata) be explained by the gene Expression Patterns of the Major Shell Matrix Proteins in the Pearl Sac? Marine Biotechnology; Jerry D.R., Kvingedal R. , Lind C. E., Brad S. Evans B. S., Taylor J.J.U., Safari A. E.

( 2012 ). Donor-oyster derived heritability estimates and the effect of genotype x environment interaction on the production of pearl quality traits in the silver-lip pearl oyster, Pinctada maxima. Aquaculture, 338-341, 66-71; Gueguen Y., Montagnani C.,

Joubert C., Marie B., Belliard C., Tayale A., Fievet J. , Levy P., Piquemal D., Marin F., Le Moullac G. , Ky C-L. , Garen P., Lo C., Saulnier D. (2013) . Recent Advances in Pearl Research Proceedings of the International Symposium on Pearl Research, 184-194) . Research on pearls formation also focuses on finding new pearl molluscs, as the freshwater mussel Anodonta woodiana (Yoshita S. S. R. , Solihin D. D., Manalu W. , Affandi R. (2013) . Nucleus Pearl Coating Process of Freshwater Mussel Anodonta woodiana (Unionidae). Hayati Journal of Biosciences , Vol . 20 No.

1, 24-30) and the seawater mussel Mytilus coruscus, edible mussel of the pacific area (Chinese patent n. CN107079856 ) , queen conch Strombus gigas (US Patent, publication n. US 2010/0251968) .

US patent N. US1328008 discloses a grafting method to produce pearls in pearl oysters, inserting in the bivalve a bead covered by mantle tissue of a donor mollusc.

Korean patent n. KR20180009761 and Chinese Patent n. identify different species involved in pearls production, as the abalone and the mussel Mytilus coruscus .

Chinese patent n. CN107568120 discloses a method for producing pearls comprising the steps of obtaining pearl nucleus for holing treatment, preparing a small mantle cell piece, inserting the nucleus after holing into a needle of a nucleus insertion tool, sticking the small mantle cell piece to the surface of the pearl nucleus, using a opening knife is used to form a cut in the nucleus position of the mantle after a freshwater mussel is opened, and then adopting a guiding member to form a nucleus- conveying channel in the epidermis of the cut in the nucleus position direction. The pearls nucleus is implanted into the mussel body, removing the nucleus insertion tool, making the freshwater mussel recuperate at first, and transferring the mussel to a freshwater aquaculture area until a nucleus pearl is formed in a pearl sac of the mussel body.

Japanese patent n. 6413929 discloses that after drilling the pearl oyster shell and implanted the nucleus, the hole is covered with a plastic or metal and the cover is connected to the shell with screws or hooks.

Chinese patent n. CN101849522 discloses a technique to improve the position for nucleus inserting and culturing the pearl.

Technical problem

The processes known in the art for the production of pearls from bivalves present several drawbacks.

In general, the pearl oyster farms undergoes several problems to produce marketable pearls, such as grafting operation that can be carried out only by a specialized technician, since the grafter skill could influence particularly the shape of the pearls and the rejected ones.

Commercially valuable pearls need approximately 15 - 24 months for the implantation. To undergo to grafting process, oysters should be least two to three years old, and before this age they are placed in nurseries, suspended metal nets by stainless steel or nylon wires until to be used for pearl culturing. Therefore, the entire procedure to obtain a pearl takes almost 4 years (Gervis M.A. and Sims N.A. The biology and Culture of Pearl Oysters. (1992) ICLARM Stud. Rev. 21, p.49; Arnaud-Haond S., E. Goyard E., Vonau V.,Herbaut C., Prou J. , Saulnier D. (2006) Pearl Formation: Persistence of the Graft During the Entire Process of Biomineralization. Marine Biotechnology 9, 113-116).

The pearl production is threatened by the risk that after the grafting operation, nucleus rejection and oyster's mortality occurs .

In the method of Japanese patent n. 6413929 the plastic or metal do not ensure that after hole covering the animal is completely isolate as the hole is perfectly closed, Moreover screws or hooks are used causing further stress to the treated animal.

In the method disclosed in the Chinese patent n. CN101849522 is not specified if, in the implanted pearl oyster, the hole is closed artificially or if the animal's self-defence mechanisms act alone to repair the damage.

In view of the drawbacks of the techniques known in the art the inventors of the present invention investigated the opportunity of producing pearl from edible bivalvia and gastropoda.

The technical problem of the present invention is to provide a process for the production of pearl from edible bivalvia and gastropoda solving the disadvantages of the known techniques.

In particular, the proposed method for the production of pearls from edible bivalves is cheap, fast and efficient, ensuring good quality of the final product.

The process of the present invention can be performed in aquafarms without reducing food production, by using the same breeding system, wherein food production and pearls production can be done contemporarily.

The process of the present invention provide a novel drilling step, performed only on the shell, which lower stress and mortality of the animals. The present inventors identified a precise area where to create a hole, in order to optimise the pearl production process without causing any damage and/or stress to the animal.

The present invention does not provide any interaction with the animal body, therefore does not fall within any prohibition top patentability.

It is well known by the person skilled in the field of the invention that bivalves are composed by a shell and a body.

The shell is produced by the body, also indicated as the soft body, by deposition of minerals .

The drilling step within the process of the present invention does not interact and does not cause any damage to the soft body, on the contrary the aim of the present invention is not to stress the animal in order leave it intact after pearl production .

Herein several definitions are reported: "The body of a mollusc is typically enclosed within a shell, and to many this dead product of the animal' s secretory activity is more familiar than the living organism itself" (V. Fretter & A. Graham, 1994. British Prosobranch Molluscs. Their Functional Anatomy and Ecology. Vol 161. Eds. Ray Society, London).

"The molluscan shell is made up basically of crystals of calcium carbonate" (T. Abbot, 1986. A guide to field identification. Seashells of North America. Eds. Golden Books, New York).

"...the inner or mother-of-pearl layer, secreted by the entire surface of the mantle, consists of parallel layers of calcium carbonate" (M. La Greca, 1998. Zoologia. Zoologia degli invertebrati . Vol. 1. Eds. UTET, Torino).

"In simple terms, the shell is best regarded as an external skeleton. As well as supporting the soft body of the mollusc, it serve as a protection" (G.T. Poppe & Y. Goto, 1991. European Seashells . Vol 1. Eds. Verlag Christa Heiranen, Germany).

Object of the invention

With reference to the claims the above technical problem is solved by providing a process for producing pearls from bivalvia and/or gastropoda comprising the following steps: a) Selecting an adult subject of bivalvia and/or gastropoda; b) Drilling the shell of the adult subject of bivalvia and/or gastropoda selected in step a) on the central-apical part of the shell to creates a hole with a diameter comprised between 3 mm and 4 mm; c) Preparing a nucleus consisting of a ball of a diameter comprised between 2 mm and 3 mm made of water resistant inert thermoplastic material mixed with powder of shell of bivalvia and/or gastropoda of the same type of the subject of bivalvia and/or gastropoda selected in step a); d) Inserting the nucleus as prepared in step c) inside the subject of bivalvia and/or gastropoda through the hole created in step b) ; e) Closing the hole created in step b) by moulding the water resistant inert thermoplastic material by heating at a temperature between 60 °C and 70 °C; f) and waiting for the time necessary for production of the final product from the bivalvia and/or gastropoda;

A further object of the present invention are Bivalvia and/or gastropoda as modified at the end step e) and used in the process .

A further object of the present invention is pearl as obtained by the process at the end of step f ) . Further features of the invention will be clear from the following detailed description with reference to the attached drawings and experimental results provided.

Brief description of the drawings

Figure 1 shows in graph the results of mortality test carried out with different techniques and different materials for the nucleus .

Figure 2 shows the morphometric analysis made on the shell of a Mytilus .

Figure 3 shows shell morphometric grid deformation and hole position in ten individuals.

Figure 4 shows shell shape landmarks and hole position and shell x-ray.

Figure 5 shows an X-ray image of a Mytilus, wherein the animal is divided in 4 quadrants and the position of the hole is indicated by a dot.

Detailed description of the invention

The process for producing pearls from bivalvia and/or gastropoda comprises the following steps: a) Selecting an adult subject of bivalvia and/or gastropoda; b) Drilling the shell of the adult subject of bivalvia and/or gastropoda selected in step a) on the central- apical part of the shell to creates a hole with a diameter comprised between and 3 mm and 4 mm; c) Preparing a nucleus consisting of a ball of a diameter comprised between 2 mm and 3 mm made of water resistant inert thermoplastic material mixed with powder of shell of bivalvia and/or gastropoda of the same type of the subject of bivalvia and/or gastropoda selected in step a) ; d) Inserting the nucleus as prepared in step c) inside the subject of bivalvia and/or gastropoda through the hole created in step b) ; e) Closing the hole created in step b) by moulding the water resistant inert thermoplastic material by heating at a temperature between 60-70 °C; f) waiting for the time necessary for production of the final product from the bivalvia and/or gastropoda;

Is also object of the present invention a pearl obtained by the process comprising the following steps: a) Selecting an adult subject of bivalvia and/or gastropoda; b) Drilling the shell of the adult subject of bivalvia and/or gastropoda selected in step a) on the central- apical part of the shell to creates a hole with a diameter comprised between and 3 mm and 4 mm; c) Preparing a nucleus consisting of a ball of a diameter comprised between 2 mm and 3 mm made of water resistant inert thermoplastic material mixed with powder of shell of bivalvia and/or gastropoda of the same type of the subject of bivalvia and/or gastropoda selected in step a) ; d) Inserting the nucleus as prepared in step c) inside the subject of bivalvia and/or gastropoda through the hole created in step b) Closing the hole created in step b) by moulding the water resistant inert thermoplastic material by heating at a temperature between 60°C and 70 °C; e) waiting for the time necessary for production of the pearl from the bivalvia and/or gastropoda;

Preferably, in the shell, the position of the hole drilled in the central-apical part of the shell is defined by coordinates x and Y,

Wherein

X is the distance on x-axis from the intersection centre 0

X is the distance on y-axis from the intersection centre 0

Wherein intersection centre 0 is the intersection between AB and CD

Wherein AB is the maximum shell length CD is maximum shell width

Wherein AB is between 6,01 cm and 6,48 cm CD is between 2,8 cm and 3,24 cm X is between 0,22 cm and 0,47 cm

Y is between 0,41 cm and 0,48 cm.

More preferably AB is 6,01 cm, CD is 2,8 cm, x is 0,22 cm and Y is 0,41 cm.

Preferably bivalvia are selected from the group consisting of Mytilida, Ostreida.

More preferably Mytilida and Ostreida are selected from the group consisting of Mytilidae, Pteriidae, Ostridae, Margaritiferae, Crassostrea. Even more preferably bivalvia are selected from the species group consisting of P. fucata, P. maxima , P. margaritifera , P. mazatlantica , P. penguin , P. fucata , P. maxima , P. margaritifera , P. mazatlantica , P. penguin , O. edulis , , C. gigas , M. margaritifera , Mytilus edulis , M. coruscus , M. galloprovincialis .

Most preferably bivalves are from the species M. galloprovincialis .

Preferably gastropods are from the family Strombidae. Most preferably gastropods are from the species S. gigas.

Preferably in step a) adult individuals of mussel M. galloprovincialis, are of age 18 months.

Preferably in step b) the hole has a diameter of 3 mm.

Preferably in step c) the ball had a diameter of 2 mm. Preferably in step e) the temperature is 60°C.

Preferably the water resistant inert thermoplastic material is selected from the group consisting of: poly ( caprolactone ) diol, poly(vinyl pivalate), poly ( t-cyclohexanedimethyl succinate, poly ( isobomyl methacrylate) and poly ( caprolactone ) . Most preferably the water resistant inert thermoplastic material is poly ( caprolactone ) diol.

In a preferred embodiment adult individuals of mussel M. galloprovincialis (age 18 months) are chosen in a mussels' farms and placed in laboratory tanks, and undergoes to acclimatization for few days. The mussels are ready to be surgically implanted. Mussels are taken out of the water, they generally attach themselves to a substrate with the byssus . Since separation may cause stress and mortality to the animal the grafting step is lead without separating them from each other. One mussel a time undergoes the grafting operation. Mussel's shell is drilled with a thin tip on the central-apical part, to creates a hole from which a ball made of Moldable plastic Thermoform composed by poly ( caprolactone ) diol, m.w. 1250, C4H803 (C6H10O2 ) n, melt at high temperature, of approximately 2-3 mm in diameter is inserted within the animal. The surgically implanted mussel return to the tank and finally put back in seawater area in the original a mussel farm. They produce the first stage of pearl in about six months.

Examples

The Moldable plastic Thermoform is composed by poly ( caprolactone ) diol, m.w. 1250, C4H803 (C6H10O2 ) n verified by ATR (Attenuated Total Reflectance) infrared spectroscopy, Moreover, the DSC (Differential Scanning Calorimetry) highlighted that the plastic material is composed by only one polymer .

The studies were conducted on the edible mussel Mytilus galloprovincialis .

Morphometric analysis was conducted to define the structure and shape of the shell (landmarks) and the hole coordinates referring to the intersection of the AB-CD axes. The software used for the morphometric analysis were tpsDIG2w32 (Rohlf FJ, 2010. tpsDig, version 2.16. Department of Ecology and Evolution, State University, New York at Stony Brook, New York) and Morphologika (O'Higgins P and Jones N (1998) Facial growth in Cercocebus torquatus : An application of three dimensional geometric morphometric techniques to the study of morphological variation. Journal of Anatomy. 193: 251-272). The results of the morphometric analysis are shown in figures 2-5.

The process of the present invention was compared with techniques known in the art.

Compared experiments were also conducted on different nucleus materials . Four different operating modes were tested on four groups of 50 adult mussels for each.

Classical grafting provides for open the valves slightly with a knife or a pointed tool and insert the nucleus into the animal. Different nucleus materials were inserted in each of the four different groups.

In the first group, the nucleus was a small ball of 2 mm in diameter of a bicomponent material made by an epoxy resin of bisphenol A and epichlorohydrin . In the second group, the nucleus was a thermoplastic ball of Moldable plastic Thermoform is composed by poly ( caprolactone ) diol, m.w. 1250,

C4H803 (C6H10O2 ) n , mixed with mussel shell powder, of the same dimension of the previous one. In the third group, the nucleus was a small fragment of donor mussel shell. Finally, in the fourth group the shell fragment was enwrapped in a mantle tissue of a donor mussel of the same species . After the operation, mussels were acclimatized in continuous flow aquarium for 24 hours and then, the survived ones transferred in the sea water. Despite the use of different materials as a nucleus, all the mussels were died after 24 hours.

As regard as the nucleus materials, the fragment shell nucleus both with and without the mantle of a donor mussel, it was always rejected. Unlike the small ball nucleus of thermoplastic and bicomponent material that were no rejected. Between these two groups of mussels, the ones grafted with the bicomponent material were all died after 12 hours from the injection. The other group was more resistant, remaining alive for up to 24 hours. The results are shown in the following table 1.

Table 1

Wherein: "Nucleus material": B = Bicomponent, T = Thermoplastic, S = Shell fragment, SD = Shell fragment in a donor tissue.

Established that with the plastic or bicomponent nucleus there were no rejections and less mortality, the process object of the present invention was tested on other two different mussel groups, each of 50 individuals. The mussels were drilled in the center of the shell and inside the holes were put the nucleus, bicomponent and shell-made for a group and thermoplastic-made for the other one. The hole on the shell in each group was closed with the thermoplastic. All the mussels with the bicomponent nucleus were died (figure 1) The mussels with thermoplastic nucleus were all still alive after six months and started to produce a first stage of pearl.

In the following table 2 are summarize all the experimental results both for the classical grafting and for the process object of the present invention. The process object of the present invention showed no nucleus rejection and long life time .

Table 2

Therefore the production of pearl according to the process object of the present invention shows several advantages compared to the classic grafting technique applied in the pacific pearls oysters.

Such as growth time since Mytilus galloprovincialis, take around 18 months to reach the adult stage, when they are ready to be grafted, while pearl oyster takes from 15 to 24 months.

Such as seed recruitment and juvenile stage since a mussel farm it is an easy process to collect the seed, just some ropes needed. Very young mussels take root on the ropes or on the socks containing the adult mussels, after the young mussels collection they are kept in a socks with a right size mesh and they are left to grow. Young pearl oysters need a different process and technical expedients. Pearl oysters needed special nurseries, suspended metal nets by stainless steel or nylon wires .

The grafting step is very easy. There is no need of a highly specialized technician and no special instrumentation, so there are not economic expenses for the company both for technician formations and for the instruments . The probability of a bad pearls quality is reduced since the process provided is a more industrialized process and there are no chemicals to use both for opening the bivalves' shell and to disinfect the graft area. There are not rejections of the inserted nucleus and no mussels died. The nucleus inserted in the mollusc from the hole is more difficult to be rejected as it is inserted in the central part of the shell, far from the opening of the valves. Moreover the thermoplastic used to close the hole does not bother the animal and is not toxic, mussels could still live quietly. The pearls production in edible mussels could be led from the same mussel farms that produce them as food product. Once the pearl has been removed, the body of the mollusc can be used in packaged products. The production of pearls from edible molluscs would thus be part of its own food production chain, unlike the pacific pearl industries that focus their production only on the pearls .

Claims

1) Process for producing pearls from bivalvia and/or gastropoda comprises the following steps: a) Selecting an adult subject of bivalvia and/or gastropoda; b) Drilling the shell of the adult subject of bivalvia and/or gastropoda selected in step a) on the central- apical part of the shell to creates a hole with a diameter comprised between and 3 mm and 4 mm; c) Preparing a nucleus consisting of a ball of a diameter comprised between 2 mm and 3 mm made of water resistant inert thermoplastic material mixed with powder of shell of bivalvia and/or gastropoda of the same type of the subject of bivalvia and/or gastropoda selected in step a) ; d) Inserting the nucleus as prepared in step c) inside the subject of bivalvia and/or gastropoda through the hole created in step b) ; e) Closing the hole created in step b) by moulding the water resistant inert thermoplastic material by heating at a temperature between 60 °C and 70 °C; f) Waiting for the time necessary for the production of the final product from the bivalvia and/or gasteropoda.

2) Process according to claim 1 wherein the position of the hole drilled in the central-apical part of the shell is defined by coordinates x and Y, wherein X is the distance on x-axis from the intersection centre 0, Y is the distance on y-axis from the intersection centre 0, Wherein intersection centre 0 is the intersection between AB and CD, Wherein AB is the maximum shell length CD is maximum shell width, Wherein AB is between 6,01 cm and 6,48 cm, CD is between 2,8 cm and 3,24 cm, X is between 0,22 cm and 0,47 cm, Y is between 0,41 cm and 0,48 cm.

3) Process according to claim 2 wherein AB is 6,01 cm, CD is 2,8 cm, x is 0,22 cm and Y is 0,41 cm.

4) Process according to claim 1 wherein bivalvia is selected from the group consisting of: Mytilid-a, Ostreida.

5) Process according to claim 3 wherein Mytilidaand Ostreida are selected from the group consisting of: Mytilidae, Pteriidae, Ostridae, Margaritiferae, Crassostrea.

6) Process according to claim 3 wherein Mytilida and Ostreida are selected from the group consisting of P. fucata, P. maxima , P. margaritifera , P. mazatlantica , P. penguin, P. fucata , P. maxima , P. margaritifera , P. mazatlantica , P. penguin, O. edulis , , C. gigas, M. margaritifera , Mytilus edulis , M. coruscus, M. galloprovincialis .

7) Process according to claim 1 wherein gastropoda are selected from the group consisting of Strombidae.

8) Process according to claim 5 where in Strombidae is S. gigas .

9) Process according to claim 1 wherein in step b) the hole has a diameter of 3 mm.

10) Process according to claim 1 wherein in step c) the ball had a diameter

mm. 11) Process according to claim 1 wherein in step e) the temperature is of 60 °C.

12) Process according to anyone of claims 1-9 wherein water resistant inert thermoplastic material is selected from the group consisting of: poly ( caprolactone ) diol, poly(vinyl pivalate), poly ( t-cyclohexanedimethyl succinate, poly ( isobomyl methacrylate) and poly ( caprolactone ) .

13) Process according to claim 10 wherein the water resistant inert thermoplastic material is poly ( caprolactone ) diol.

14) Bivalvia and/or gastropoda as used in the process of anyone of claims 1-11 and as modified at the end of step e) .

15) Pearl obtained by the process comprising the following steps : a) Selecting an adult subject of bivalvia and/or gastropoda; b) Drilling the shell of the adult subject of bivalvia and/or gastropoda selected in step a) on the central-apical part of the shell to creates a hole with a diameter comprised between and 3 mm and 4 mm; c) Preparing a nucleus consisting of a ball of a diameter comprised between 2 mm and 3 mm made of water resistant inert thermoplastic material mixed with powder of shell of bivalvia and/or gastropoda of the same type of the subject of bivalvia and/or gastropoda selected in step a); d) Inserting the nucleus as prepared in step c) inside the subject of bivalvia and/or gastropoda through the hole created in step b) ; e) Closing the hole created in step b) by moulding the water resistant inert thermoplastic material by heating at a temperature between 60 °C and 70 °C; f) Waiting for the time necessary for the production of the pearl .