Performing Department
WILDLIFE & FISHERIES SCIENCES
Non Technical Summary
The U.S. is the primary provider of freshwater mussel shell nuclei and a major consumer of pearls, but the economic benefits of pearl culture accrue mainly to foreign companies, while environmental and economic externalities negatively affect the economy and environment of the Southeastern States. The purpose of this project is to develop the tools and methodology required to initiate pearl culture in Texas.
Animal Health Component
40%
Research Effort Categories
Basic
30%
Applied
40%
Developmental
30%
Goals / Objectives
Economic participation of the U.S. in the global pearl industry has been minimal in terms of economic benefits received, although critical in terms of supporting the industry. The U.S. is the primary provider of freshwater shell mussel shell nucleus and a major consumer of pearls, but economic benefits accrue mainly to foreign companies while environmental and economic externalities affect the economy and environment of the Southeastern States. The economic role of the U.S. mussel shell industry and aquaculture sector can be enhanced if the mussel shellfishery is stabilized and if options to extract higher returns for the stakeholders are explored. More than 300 species of freshwater mussels are found in the watersheds of the Southeastern U.S., of which at least 12 have been identified as potential pearl farming species. The results of this proposal will establish economic parameters to enhance coastal economic development and together with other sea grant researchers,
establish a cooperative and comprehensive research program aimed at the enhancement of implantation technology . Pearl farming is poised to make significant economic contributions to the U.S. economy. Currently, cultured pearls are primarily produced by marine pearl oysters. Cultured pearls are formed by the deposition of nacre onto a spherical nucleus. The tissue that secretes the nacre (taken from a donor mussel), as well as the nucleus itself, must be implanted into a living mussel that will serve as the host for pearl production. Rejection, infection, inferior pearls, and mortality are among the potential pitfalls. For decades, techniques for successful implantation of oysters remained a closely guarded secret of the Japanese. Now, biologists are beginning to understand some of this process and these techniques are being made available to people around the world interested in developing pearl production capabilities. Much remains to be understood about implantation in marine
bivalves, however, and far less is known about the process with freshwater mussels. Thus, the expansion of marine and freshwater pearl farming in the U.S. holds great promise. However, the biology, culture and grafting technology related to pearl production has been closely held trade secrets until recently, and much of the basic technology is still unavailable. Most critically, basic knowledge of the physiology and biochemistry of nacre and pearl formation remains patchy. Lack of published data in these areas has hampered pearl farmers, nucleus producers, and sea grant personnel from providing technical assistance to the industry. Specific Objectives 1.Develop 2 economically viable pearl demonstration farms. 2.Establish implantation procedures for 3 pearl producing species in Texas. 3.Initiate research into pearl sac development.
Project Methods
Our current research indicates that 2000 implanted animals a unit that scales linearly relative to implantation and culture costs up to a 30,000 animal farm. Therefore we have chosen to establish 2 demonstration projects of 2000 animals each using the washboard (Megalonaias nervosa). The first will be established on a rice farm. The second, in the Colorado watershed, will be established in cooperation with Aquaculture America. Grafting methods for freshwater pearl production differ from those used for marine pearl oysters. Grafting is the key technology in pearl production. Pearl farming is unique in that it is the only form of aquaculture that relies on the use of surgical methods and the induction of biomineralization. Formation of cultured pearls is initiated by a surgical procedure, in which a shell bead is implanted in the tissues of a host bivalve, along with a piece of mantle tissue taken from a donor bivalve. The grafted tissue grows around the nucleus, forming
the pearl sac. The lining of the pearl sac contains epithelial cells that deposit layers of nacre around the nucleus, forming a cultured pearl. The waters of Texas are inhabited by at least 12 pearl producing mussel species. Our research indicates that the implantation procedures for each may be unique. In particular, our results indicate that anesthesia procedures may differ among species. Anesthesia is much more important in mussel implantations than among oysters since mussels have both anterior and posterior adductor muscles. Our preliminary results indicate that the vast majority of post surgical mortalities occur because one or both of these muscles are torn while prying the valves open. We will conduct a series of experiments to test a variety of molluscan anesthetics for effectiveness and temperature dependencies. The site of implantation and the instruments used to insert the nuclei differ among species due largely to anatomical variations. Our goal is to establish the
procedures and tools to add 3 additional species, giving potential farmers 4 species to work with. Likely candidates include several members of the maple leaf family, pimplebacks and bank climbers. Finally, will initiate a sustainable research program designed to enhance the technology of pearl production. We will concentrate on the characterization of pearl sac development by histological and molecular techniques. In addition growth factors will be tested to determine if tissue growth is accelerated when exposed to these substances as a means of increasing the rate of pearl sac formation. In essence, the formation of the pearl sac is a wound healing process. Thus, like in wound healing, it is thought that the faster the pearl sac forms, the more likely a desirable outcome will be.