Producing Triploid Oysters

View the project final report

Commodities

• Animals: shellfish

Practices

• Animal Production: aquaculture

Farming of the Pacific Oyster (Crassostrea gigas) is an important part of the economies and cultures of the West Coast states. Oyster culture supports thousands of jobs in rural areas and provides locally produced seafood at a time when the U.S. imports approximately 90% of its seafood. Oysters are also critical in maintaining water quality and provide other important ecological services in coastal areas. The West Coast oyster industry faces numerous challenges such as ocean acidification impacts, rising labor costs, and permitting difficulties, but now faces a challenge that could almost immediately undermine the entire industry as a key patent expires. The patent (#US5824841 A) on the use of tetraploid oysters expires in January 2015, an event which might otherwise go unnoticed, were it not for the fact that the West Coast industry is heavily dependent on the use of tetraploid oysters to produce triploid oysters, the mainstay of the industry. Triploid oysters (which contain three sets of chromosomes) are essentially sterile, a characteristic that makes them harvestable year round. These generally sterile oysters do not become “spawny” (e.g. full of eggs or sperm) or flaccid and thin during the warmer months, as do fertile diploid oysters. Without triploid oysters, farmers will not be able to harvest during much of the year, thus threatening the economic viability of the farms, hatcheries, and processors. While the importance of the future availability of triploid oysters cannot be underestimated, neither can the current difficulty and cost of obtaining triploid oyster seed. While triploid oysters can in theory be produced using a combination of chemicals, pressure, heat, and other inducers at a precise moment in oyster embryo development, these methods are not efficacious enough to obtain the benchmark of at least 90% triploid progeny to assure summer harvests. The only reliable method of producing greater than 90% triploid oyster progeny is to utilize tetraploid oyster sperm to fertilize diploid eggs. In order for oyster hatcheries to obtain tetraploid oysters for this purpose, a license must be obtained from the 4C’s company. This company was created by Rutgers University, the assignee of the patent for tetraploid oysters, to manage this valuable intellectual property. To fully understand the difficulty in which the West Coast oyster industry now finds itself, a bit of history must be recounted. In 1993, Rutgers University was awarded a patent for the tetraploid oysters with Drs. Ximing Guo and Standish Allan as co-inventors. At this point, the evolution of the use of tetraploid oysters on the East Coast and the West Coast diverged. The two inventors went on to develop thriving research programs at Rutgers University and the Virginia Institute of Marine Science (VIMS), respectively. One of the outcomes of their continued research on the genetics of the Eastern Oyster (Crassostrea virginica), East Coast farmers, and hatcheries now has access to improved lines of diploid and triploid oysters that demonstrated high performance and disease resistance in both high and low salinity environments. VIMS regularly produces and distributes genetically selected tetraploid and triploid oysters for use in hatcheries and on farms. In contrast, the intellectual property represented by the patented tetraploid oyster languished on the West Coast. The reasons for this are subject to conjecture, but the outcome is that one partner hatchery has been used by 4C’s to produce and distribute tetraploid oysters to the rest of the industry. The results have been less than ideal. For example, even once a license for tetraploid use has been granted to a West Coast hatchery, obtaining verified tetraploid broodstock from the distributor is difficult. Often none is available. The tetraploids also produce low-viability sperm and the resulting triploid progeny is weak and difficult to raise to maturity in the hatchery. The triploid progeny also exhibit early mortality, often dying en masse by the end of the second summer of growth. The cause of this mortality is unknown, but is suspected to be related to the probable inbreeding of the tetraploid stock. No information is released on the genetics of the broodstock. Moreover, licensees are required to propagate their own tetraploid broodstock after receiving the first animals, which is difficult due to their fragility. Now that the patent for tetraploids oysters is about to expire, research and development efforts can resume to advance the development and use of tetraploid Pacific Oysters, thus making production of triploid oysters more efficient, reliable, and available. If more reliable methods of tetraploid production are developed and a readily available supply of higher quality broodstock is produced, the continued supply of triploid oysters will be assured. Moreover, developing the capability to produce tetraploids de novo rather than inbreeding existing stocks allows researchers and hatchery managers to continually improve tetraploid lines and integrate tetraploids into breeding programs. This will benefit all stakeholders in the West Coast Shellfish industry which depend on the availability of triploid seed, but it also improves the resilience of the industry since breeding can help adapt oysters to climate change impacts and disease and optimize performance traits. Two producers (Hawaiian Shellfish LLC) and Paepae o He`eia are partnering with the Pacific Aquaculture and Coastal Resources Center (PACRC) at the University of Hawaii Hilo (UHH) to execute this work. The team is fortunate in obtaining the technical assistance of Dr. Ximing Guo, co-inventor of the tetraploid production methods, and Dr. Anu Frank-Lawale, who most recently served as the lead Breeding Manager for the oyster improvement program at VIMS.

The overall goal is to conduct research to develop more reliable methods and refine existing methods for de novo tetraploid oyster production suited for commercial and research hatcheries. This will ensure that tetraploid and triploid oyster supply will continue and increase access for farmers, hatchery managers, and researchers. It will also allow tetraploids to be integrated into West Coast breeding programs which currently focus on diploids. Hatchery managers, researchers, and technicians associated with the Hawaiian Shellfish and the PACRC hatcheries will be trained in methods to produce tetraploids by the co-inventor of the original methods. A manual will be produced to explicitly detail these methods and how to adapt to variable conditions between hatcheries. Associated stakeholders will be trained in holding and tracking tetraploid broodstock performance, as well as monitoring the performance of resulting triploid progeny. These actions constitute an important component of a broader effort between Hawaiian Shellfish LLC, PACRC, and the Molluscan Broodstock Program (MBP) at Oregon State University to develop an oyster industry breeding plan for the benefit of the Western Region (including Hawaii), as well as to incorporate tetraploids into the MBP’s existing genetic selection program.

Objective 1: Conduct research to develop reliable and effective methods for tetraploid oyster production. This research will be conducted with the assistance of Dr. Ximing Guo (Rutgers University), one of the co-inventors of the original patent for the tetraploid oysters. He will be assisted by Dr. Maria Haws (PACRC) who has also conducted trials on de novo tetraploid production and methods for production of triploids. Dr. Frank-Lawale will advise on issues related to breeding.

Objective 2: Grow out and monitor performance of tetraploid oysters with associated producers. Given that genetic selection for oysters is complicated by the magnitude of genetic x environmental interaction found in this species, i.e. the same strain of oyster may perform very differently in different environments, it is important that the tetraploid specimens be monitored under the conditions in which their progeny will develop. We will grow out and monitor tetraploids in four locations: Goosepoint Farm in Washington, He`eia Hawaiian Fishpond in Oahu, Keawanui Fishpond in Molokai, and at the PACRC. Partners will be trained in monitoring and data collection methods.

Objective 3: Produce a manual and video clips that describe tetraploid production methods in sufficient detail that other hatchery operators or researchers can replicate them. Although an extensive body of scientific literature exists for tetraploid and triploid production methods, extensive trials at the PACRC hatchery demonstrates that the methods contained within are not detailed or complete enough to allow for replication. We will produce a manual that contains complete and detailed methods to allow other hatchery operators to more easily replicate these critically needed methods.