Production of tetraploid pearl oyster (Pinctada martensii Dunker) by inhibiting the first polar body in eggs from triploids

All previous attempts to produce viable tetraploid pearl oyster (Pinctada m artensii Dunker) by inhibiting the first polar body and the first mitosis h ave failed. This study aims to test the possibility of producing viable tet raploids by the intentional process of crossing triploid females and diploi d males following the inhibition of the first polar body. When 0.5mg/L CB w as applied to inhibit the release of the first polar body, about 16.69% of embryos developed as tetraploids, the majority of embryos were aneuploids ( 65.48%); about 82% embryos developed as aneuploids in the control group (TD 1), but no tetraploid embryos were found. Ploidy of embryos in the TD1 grou p mainly fell between 2n and 3n, bur ranged from 2n to 5n in the TDCB group . During rearing period, larvae died heavily. At Day 51 post-fertilization, 2125 spat were harvested, averaging 0.033% of D-larvae cultured. Chromosom e analysis revealed that 115 one-year-old pearl oysters consisted of 28.70% diploids (n = 33), 40.87% triploids (n = 47), 1.74% tetraploids (n = 2) an d 28.70% aneuploids (n = 33) with 29, 30, 40, 41, and 43 chromosomes. Compa rison of growth showed that aneuploids was not significantly different from diploids in both shell length and body weight (P > 0.1), but significantly smaller than triploids (P < 0.05). This study demonstrated that the produc tion of viable tetraploid pearl oysters with eggs from triploids is possibl e, and certain levels of aneuploidy can be tolerated in this species.