ALL-TRIPLOID PACIFIC OYSTERS (CRASSOSTREA-GIGAS THUNBERG) PRODUCED BYMATING TETRAPLOIDS AND DIPLOIDS

To document the reproductive characteristics of tetraploids and determ ine whether they can be used for triploid production, factorial crosse s 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). Su rvival to spat in TD and DT groups was about the same as in normal dip loids, and significantly higher than in the 3nCB and TT groups, As det ermined by flow cytometry, all surviving oysters from DT and TD crosse s were triploids, and only 46% of oysters from the 3nCB group were tri ploids. ?T crosses produced primarily tetraploids despite low survival . At 8 and 10 months of age, triploid oysters from DT and TD groups we re 13-51% larger than normal diploids, possibly due to polyploid gigan tism. These results suggest that mating tetraploids and diploids is th e 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.