Production of triploid Pacific oyster (Crassostrea gigas) spat. A practical manual.

Naturally spawned oysters are typically diploid, each cell containing two sets of chromosomes. Diploid oysters exhibit seasonal variability in condition because they spawn during the summer months following a period of ripening as sea temperatures warm. Often this coincides with the peak period for selling oysters in many countries. Triploid oysters contain three sets of chromosomes and because they are for the most part sterile, they can maintain suitable market quality throughout the year and have organoleptic qualities that are preferred by many consumers. Growth of triploids is generally much faster than diploids grown under the same conditions. For these reasons, many hatcheries produce triploid oysters. Triploid oysters can be readily produced in hatcheries using either direct induction techniques or by first producing tetraploid oysters and then using sperm from male tetraploids to fertilise eggs from diploid females. There are several different direct techniques to induce triploidy, including physical treatments such as pressure, temperature or salinity shock or chemical treatments using either cytochalasin B or 6-Dimethyl aminopurine (6-DMAP).