Scientists at FAU’s Harbor Branch Oceanographic Institute achieve a major breakthrough in the culturing of queen conch pearls, which hitherto had defied other research scientists and pearl culturists.

Research Scientists at the Florida Atlantic University’s Harbor Branch Oceanographic Institute have achieved a sensational breakthrough by successfully culturing high-quality queen conch pearls, a feat that had evaded research scientists and pearl culturists for over 25 years, according to a report published on November 3, 2009, on the Florida Atlantic University’s Harbor Branch website

Queen Conches are an endangered species after continuous exploitation for centuries as a source of food

 The Queen Conch (Strombus gigas), is a gastropod mollusk, a sea-snail, whose geographic range is the neo-tropical Atlantic waters of the Caribbean and the Gulf of Mexico. These sea-snails are found in the waters off Bermuda, Southern Florida, Southern Mexico, the entire Caribbean region, Venezuela and Brazil. The queen conch meat is considered a delicacy, and had been consistently harvested by people living in the region since ancient times. The queen conch fishery had been a thriving industry in the region until the 1960s, and in the Caribbean the annual wholesale value of its output had been around US $60 million. Over fishing and poaching to meet the unprecedented local and international demand for conch meat, and habitat degradation such as loss of nursery habitats like shallow-water sea grass meadows, led to rapid decline in populations of queen conch throughout its range, that led to restrictions and total ban on fishing in many countries, including the US State of Florida, Bermuda, Cuba, Colombia, Venezuela, Mexico, Virgin Islands, Antilles etc. The Queen Conch is now considered an endangered species and listed in Appendix II of the CITES (Convention for the International Trade on Endangered Species).

Queen conch- Strombus gigas

Queen conch- Strombus gigas

Credit: FAU’s Harbor Branch Oceanographic Institute

Conch pearls are a by product of the queen conch fishery

While the queen conch was mainly harvested as a source of food since ancient times, an important by product of this industry was the occasional conch pearl that was found in some of the sea-snails. The frequency of occurrence of these pearls was about 1 in 10,000 snails, out of which only 1 in 100 was of gem quality. Thus, good quality conch pearls were indeed very rare, with a probability of occurrence of 1 in 1,000,000. Yet the annual catch of queen conches was so enormous, that a considerable quantity of these pearls continued to be produced annually, even after the demand for such pearls decreased after its initial popularity during the Belle Époque period from 1901 to 1915.

CIBJO definition of conch pearls

The CIBJO (The World Jewelry Confederation) defines conch pearls as non-nacreous pearls consisting of calcium carbonate arranged concentrically in a crossed lamellar micro-architecture. This structural characteristic usually produces a flame-like surface pattern and porcellaneous sheen. Such pearls are produced by various gastropods including the Queen Conch (Strombus gigas), Horse Conch (Pleuroploca gigantea), and the Emperor Helmet (Cassis madagasgerensis).

Conch pearls are non-nacreous because nacre, the substance that is responsible for the luster and iridescence of nacreous pearls are not formed in these pearls. Hence non-nacreous pearls have a matte-like appearance of porcelain or ceramic, and are described as porcellaneous. However, in the case of conch pearls, the lack of luster and iridescence, seem to be compensated by another spectacular shimmering effect on the surface, known as a “flame structure.” This is an optical effect, a form of chatoyancy caused by the interaction of light, with microcrystalline fibers of calcite (crystalline calcium carbonate), arranged in concentric layers in a crossed lamellar pattern. The shimmering effect of the “flame structure” like a fire burning on the surface, is so spectacular, that it surpasses the luster and iridescence of some low grade nacreous pearls. 

The popularity of conch pearls drop after the Belle epoque period, and the pearls become valueless

The successful production of cultured Akoya pearls in Japan, in the 1920s, spelt the doom of the natural pearl industries, in the traditional pearl producing areas of the world, such the Persian Gulf, the Red Sea and the Gulf of Mannar. The popularity of natural conch pearls also decreased after this, due to the availability of cheap alternatives. However, the exploitation of the queen conch sea-snail continued in the Caribbean and the Gulf of Mexico, on an unprecedented scale, with the output increasing annually, not for the conch pearls, but for their delicious meat, for which there was an ever increasing demand both in the region as well as internationally. Thus, conch pearls continued to be produced in the region, but there were no takers for these pearls, due to the drastic drop in demand.

Conch pearls become a collectors item after they lose their commercial value

Conch pearls were now purchased only by connoisseurs and collectors, as there was no commercial value for the pearls. One such collector was Susan Hendrickson, the marine archaeologist, paleontologist and professional diver, who shot into international fame in 1990 for her discovery of the most complete fossil skeleton of T. Rex, in the Black Hills of South Dakota. During her diving expeditions to the Caribbean, she developed an interest in conch pearls, which were available abundantly in the region and began a collection, which eventually became one of the largest collections of conch pearls in the world.

Recent surge in popularity of conch pearls

There has been a surge in popularity of conch pearls in recent times. Among the reasons attributed for the increase in popularity of conch pearls are, a general increase in demand for natural pearls in a market dominated by cultured for over eight decades; the rarity of occurrence of conch pearls; the availability of conch pearls in a wide array of colors, such as pink, white, yellow, brown and golden, a salmon-colored orange-pink being the most sought after color; the presence of the unique flame structure, in the pinkish and whitish tones of conch pearls that added to their value; the high specific gravity, hardness and resistance to wear and tear compared to other pearls. Susan Hendrickson, who had the largest conch pearl collection in the world also made a significant contribution to the popularity of the pearls by going into partnership with the renowned Geneva-based jewelry manufacturer Georges Ruiz, to produce conch pearl jewelry and popularize their usage.

Previous attempts to culture conch pearls

Several attempts had been made by pearl culturists and scientists, from countries in the geographic range of the sea-snail, to culture conch pearls during the last 25 years. However, none of these attempts had been successful, probably due to the sensitivity of the sea-snail to the traditional pearl seeding techniques and the difficulty in gaining access to the gonads of the sea-snail, where pearls are usually cultured, due to the spiral shape of its shell.

The successful breakthrough in culturing conch pearls was achieved by scientists, Dr. Héctor Acosta-Salmón and Dr. Megan Davis of FAU/HBOI

The successful breakthrough in the culturing of conch pearls came as a result of around two years of research and experimentation carried out by scientists, Dr. Héctor Acosta-Salmón and Dr. Megan Davis from Florida Atlantic University’s Harbor Branch Oceanographic Institute. The two scientists who are considered as the co-inventors of the novel and proprietary seeding techniques to produce beaded and non-beaded cultured pearls from the queen conch, have successfully produced more than 200 high-quality cultured conch pearls applying this technique. The achievement of the two scientists have been hailed as  significant and comparable to Mikimoto’s successful culturing of Akoya pearls in 1916, that revolutionized the international pearl industry, making pearls available and affordable to the common man, previously enjoyed only by a privileged few. Like cultured Akoya pearls, the new discovery gives a unique opportunity for the introduction of a new and much-sought-after pearl to the industry, that has the potential of galvanizing the cultured pearl industry.

Drs. Megan Davis and Héctor Acosta-Salmón

Drs. Megan Davis and Héctor Acosta-Salmón

Credit: FAU’s Harbor Branch Oceanographic Institute

The seeding techniques used were modification of the seeding techniques used for producing saltwater and freshwater pearls

Cultured pearls are of two types – beaded (nucleated) and non-beaded (non-nucleated). Nucleated pearls are produced in saltwater oysters and non-nucleated pearls are produced in freshwater mussels. Nucleated pearls are produced by inserting a spherical shell nucleus, usually obtained from the shell of a freshwater mussel, into the gonad or mantle tissue of a recipient saltwater oyster, followed by a piece of mantle tissue obtained from  a sacrificial oyster. Non-nucleated pearls are produced in freshwater mussels by inserting only a piece of mantle tissue into the mantle or gonad of a recipient freshwater mussel. In the production of nucleated pearls from saltwater oysters, usually only a single grafting is possible at a time, but in the case of non-nucleated pearls produced in freshwater mussels, several graftings are possible at a time, producing many pearls. According to Dr. Héctor Acosta-Salmón two different seeding techniques were used in inducing pearl formation in the queen conch. One was a modification of the conventional technique used to produce cultured pearls in freshwater mussels. This was obviously for the production of non-beaded cultured conch pearls. The second was a modification of the conventional technique used for the production of pearls in saltwater pearl oysters, and was undoubtedly for the production of beaded cultured conch pearls. Apart from this, details of how the two modified techniques were carried out; how the inaccessible gonads were approached; how the harvest was taken without killing the snail etc. are not disclosed.

The culturing process developed by the scientists are efficient and environmentally sustainable

The seeding techniques developed by the two scientists were superior to the techniques used in the culturing of other pearls due to two reasons. 1) The technique ensured a 100% survival rate of queen conches after seeding, unlike in other techniques where a certain percentage of the seeded mollusks perished soon after seeding. 2) After harvesting the first pearl the queen conch can be used again for culturing a second pearl. Thus the continued survival of the queen conch during the first and second culturing periods, makes this process more efficient and environmentally sustainable, especially in the light of the dwindling populations of wild queen conches in their natural range due to over fishing, causing the species to be listed as endangered under CITES.

The natural habitat, the feeding habit and growth of queen conches

Queen conches attain their maximum growth and size when they are around 3 to 5 years old. They can reach a maximum length of about 30 cm (12 inches), attaining a weight of about 2.3 kg (5 lbs). In their natural habitat, they can have a life span of about 30-40 years. The habitat of queen conches are the shallow sea grass beds, consisting of turtle grass (Thalassia)  and Manatee grass (Cymodocea), in the warm and shallow waters of the sub-tidal zone, at depths of 1 to 30 meters. However, the main source of food of the adult conches are the algae associated with the sea grass, such as Cladophora and Polysiphonia. The veliger larvae survive mainly on plankton floating in the environment. It is their herbivorous feeding habit, that confines them to shallow and warm waters, with plenty of sunlight, known as the “photic zone” that supports the luxuriant growth of sea grass, and algae that are associated with it.

The size of the cultured pearls produced depends on the size of the bead and the culture time

 The first step in attempting the culturing of pearls in queen conches  was the farming of sufficient numbers of queen conches in aquaculture tanks, in the aquaculture facility at FAU/HBOI. The process begins with eggs laid by adult queen conches raised in captivity. The eggs hatch to form veliger larvae, which after a short period settles down and  transforms into a young shell, which is about 1 cm in length in 3 months. The young shell grows rapidly and in 12 months attains a length of 10 cm. The shell continues to grow until it is about 3 to 4 years old, when the length of the shell is between 20 to 30 cm. The shell then stops growing and begins to form a broad flared lip, an indication that the conch has attained maturity and is now ready for reproduction. It is not known at which stage in its growth the queen conches are seeded to produce cultured pearls, but in all probability it must be after the conch had attained maturity. The researches found that the size of the cultured pearls produced, was controlled by the size of the bead and the duration of the culture period. They experimented with culture times varying from 6 months to 2 years, and found that as the culture time increases, the size of the cultured pearl also increases.

Characteristics of the cultured conch pearls produced

The cultured conch pearls produced by the Acosta-Salmón and  Megan Davis technique were of the highest quality, and had a variety of shapes, such as oval or egg-shaped, spherical, near-spherical, button-shaped and baroque. Most of the pearls had a pink or rose color, one of the most popular colors in conch pearls. The pearls also have the spectacular flame structure characteristic of rose-colored conch pearls, which compensates for the lack of luster, characteristic of nacreous pearls.

Some cultured pearls produced at harbor branch

Some cultured pearls produced at harbor branch

The cultured conch pearls are handed over to the GIA for testing at its laboratories, and the results of these tests are to be published in a future issue of Gems & Gemology, published by the GIA

The FAU/HBOI handed over the cultured conch pearls to the Gemological Institute of America (GIA) for extensive testing at its state-of-the-art laboratories, using techniques, that included conventional gemological examination, determination of the chemical composition, spectroscopy, spectrometry and microscopy. It is said that the GIA together with the FAU/HBOI are planning to publish the results of these tests in one of the upcoming issues of the GIA’s scientific journal, “Gems & Gemology.” According to Tom Moses, the senior vice-president of the GIA Laboratory and Research, the culturing of conch pearls was a significant development for the pearl industry. He further stated hat scientists at the GIA were very excited at having the opportunity to closely examine the unique cultured conch pearls in their laboratory. He said that several of the pearls examined were truly top-quality gems, and the GIA was now busy trying to work out identification criteria, to separate queen conch cultured pearls from their natural counterparts.

Dr Héctor Acosta-Salmón and Dr. Megan Davis set the twin records for the first conch pearls as well as the first non-nacreous pearls to be ever cultured

There are many different types of non-nacreous pearls, produced both from bivalve as well as univalve mollusks. Among the bivalve non-nacreous pearls are quahog pearls, scallop pearls and giant clam pearls. Non-nacreous pearls produced by univalve mollusks (Gastropoda) such as sea-snails, include the queen-conch pearls, horse-conch pearls and melo-melo pearls. However, none of these non-nacreous pearls have ever been  successfully cultured before. Thus, Dr. Héctor Acosta-Salmón’s and Dr Megan Davis’ achievement in successfully culturing conch pearls, apart from setting the record as the first conch pearls to be ever cultured, also sts the record for the first non-nacreous pearls to be ever cultured.

The significance of the research work carried out by FAU/HBOI

As the queen conch was listed as an endangered species by CITES after continuous commercial exploitation for its meat, a ban has been imposed on its fishing by many countries in its natural geographic range, including the State of Florida, where the research on the culturing of conch pearls were conducted. Thus the scientists of FAU/HBOI had to first learn how to spawn and grow queen conches in captivity, so that they do not violate the ban on the fishing of wild stocks. Dr. Megan Davis made a significant contribution in this regard, by making use of her wealth of experience in aquaculture and marine science. Not only were the scientists of FAU/HBOI able to raise queen conches in captivity, but they also learnt how to make them spawn in captivity, thus enabling queen conches to complete their entire life cycle in captivity. This enabled FAU/HBOI to conform to the ban imposed by CITES, and conduct their research work entirely on farm raised queen conches.

The other singular achievement of the scientists of FAU/HBOI was the development of techniques for seeding queen conches, with their peculiar twisted anatomy, that made access to the gonads virtually impossible, and was one of the main reasons that led to the failure of earlier attempts to culture conch pearls. Besides this another important achievement of the FAU/HBOI scientists was the development of a technique for harvesting cultured pearls from seeded conches without killing them, so that they could be used again for a second seeding. This is also an important development in the light of the restrictions placed on the fishing of wild stocks.

Whenever the techniques developed by research scientists of FAU/HBOI are employed on a commercial basis to culture conch pearls, such efforts have to be based entirely on queen conches farmed in tanks by aquaculture, at least until the ban on the fishing of wild stocks are lifted. Thus the technology of farming queen conches by aquaculture, become as important as the new proprietary seeding techniques for producing cultured conch pearls, and their non-lethal harvesting. Both processes should go hand in hand in order to run a successful commercial venture to culture conch pearls by aquaculture.

Profile of the Inventors

Dr. Héctor Acosta-Salmón, Ph.D.

Dr Héctor Acosta-Salmón is a research scientist attached to the FAU/HBOI in Florida, with a wealth of experience on all aspects of pearl culture of more than 12 years. His research experience in pearl culture, covers all the commercial species of pearl oysters such as the Akoya oyster (Pinctada fucata), the Black-lip oyster (Pinctada margaritifera), the Silver-lip oyster (Pinctada maxima), found in the Western Pacific, and the Rainbow-lip oyster and the Panamian pearl oyster (Pinctada imbricata) found in the Eastern Pacific. He did his doctoral studies at James Cook University in Australia, focusing on pearl oyster brood stock management and pearl quality. He joined FAU/HBOI in 2006, serving as a post-doctoral investigator, and applying his knowledge on pearl culture technology, during his post-doctoral studies and research. During his tenure with FAU/HBOI he concentrated his research efforts in developing techniques to culture queen-conch pearls, something that had eluded scientists for over two decades. In addition to his work as a post-doctoral investigator, he also served as an assistant research professor at FAU/HBOI until 2009. He is now associate scientist at Centro de Investigaciones Biológicas del Noroeste in La Paz, B.C.S., Mexico.

Dr Megan Davis Ph.D.

Dr. Megan Davis has longtime experience in aquaculture and marine science, lasting over 30 years. While working on a commercial queen conch farm co-founded by her in the Turks and Caicos Islands, she developed commercial culture of conch from eggs to juveniles and then adults. She joined FAU/HBOI in 1996, and was later appointed as director for aquaculture and stock enhancement. In the year 2000, she successfully led an effort for inducing egg laying in tank-reared conch, thus enabling the entire life cycle of the queen conch to be completed in captivity in aquaculture. This enabled the farming of sufficient numbers of  queen conches in captivity that was subsequently used in the research activities aimed at culturing conch pearls. Her aquaculture skills with queen conch, contributed in no small measure for the successful culturing of queen conch pearls.

Apart from the queen conch she has also done extensive research on the aquaculture of spiny lobsters and marine fish. She has directed her research efforts to develop aquaculture species for food and stock enhancement, that eases fishing pressure on wild stocks that are becoming scarce. Her efforts are also geared at producing aquaculture species and systems, that are cost effective, energy efficient and environmentally sustainable. She has also been actively involved in aquaculture retraining and educational outreach programs, assisting individuals in advancing the aquaculture industry.

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Related :-

1) Queen Mary Conch Pearl Brooch

2) Susan Hendrickson’s Conch Pearls

External Links :- 

1) Scientists at FAU’s Harbor Branch Oceanographic Institute are the First to Unlock the Mystery of Creating High-quality Cultured Pearls from the Queen Conch – 

References :-

1) Scientists at FAU’s Harbor Branch Oceanographic Institute are the First to Unlock the Mystery of Creating High-quality Cultured Pearls from the Queen Conch –

2) The Palm Beach Post – Harbor Branch researches find way to culture conch pearls – by Jeff Ostrowsky.

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