All-triploid Pacific oysters (Crassostrea gigas Thunberg) produced by mating tetraploids and diploids

To document the reproductive characteristics of tetraploids and determine whether they can be used for triploid production, factorial crosses were made between diploids (D) and tetraploids (T), producing DD, DT, TD and ?T groups (female listed first). A normal triploid group was also produced by blocking polar body II with cytochalasin B (3nCB). Survival to spat in TD and DT groups was about the same as in normal diploids, and significantly higher than in the 3nCB and TT groups, As determined by flow cytometry, all surviving oysters from DT and TD crosses were triploids, and only 46% of oysters from the 3nCB group were triploids. ?T crosses produced primarily tetraploids despite low survival. At 8 and 10 months of age, triploid oysters from DT and TD groups were 13-51% larger than normal diploids, possibly due to polyploid gigantism. These results suggest that mating tetraploids and diploids is the best method for triploid production, and triploids produced in this way are better suited for aquaculture than those produced by altering meiosis and are ideal for population control.