Principles of Genetics and Breeding

8.1.5. Polyploidy in shellfishes

The techniques for creating triploid bivalves were first developed in the early 1980s.

• Stanley et al. (1981) succeeded in creating the first triploids using the American (Eastern) oyster and, since then, shellfish polyploidy has been a research priority.
• Polyploidy is highly regarded in China and has been studied in close to 30 shellfish species, including Pacific oysters, Chinese scallop (Chlamys farreri), pearl oyster, and abalone (Haliotis discus hannai).
• The benefits of triploids vary with species, from larger adductor muscles in scallops to increased survival in the Chinese pearl oyster (Pinctada martensi).
• Use of triploids in aquaculture can be advantageous when reproductive efforts negatively affect growth, survival, or product quality.
• For example, during the spawning season, the majority of oyster’s energy is directed toward reproduction, and flesh palatability is reduced as gonad replaces stored glycogen.
• Triploid oyster breeding has developed into an industry in coastal China, with triploid oysters exhibiting increased flesh quality and growth compared to diploids: triploid Pacific oysters are 17% larger than diploids prior to spawning and more than 30% larger after spawning.

Besides advantages such as increased growth rates, use of sterile triploids in aquaculture can help protect the genetic diversity of native populations and prevent establishment of populations of escaped organisms. This could be particularly relevant in addressing concerns over use of transgenic organisms in the aquaculture industry and their possible escapement and subsequent mating with wild brood stocks.