Induction of Gynogenetic Diploids the Tropical Oyster, Crassostrea belcheri 1873 (Ostreids: Ostreoidea)

Abstract

The induction of diploid gynogenesis in the Tropical oyster, Crassostrea belcheri 1873, was carried out through two main experiments: 1) the destruction of spermatozoa DNA using ultraviolet (UV) irradiation, and 2) the induction of gynogenetic diploids. UV light source was placed 30 cm over the sperm for various durations, including 0 (control), 30, 60, 90, and 120 seconds. The study revealed that the highest survival rate was observed in trochophore at 90 minutes (42.5 ± 2.50%) compared to the normal control C. belcheri (p>0.05). Based on cytogenetic study, haploid (n=10), diploid (2n=20), and aneuploid were observed in all trials, while only diploid (2n=20) could be seen in the control group. Diploid gynogenesis was induced using 100 µmol 6-DMAP for 10 minutes. The study found that the survival rate and developmental stages in both trochophore and D-shape were gradually decreasing as the duration of UV rays increased. The highest survival rate of trochophore in the control group was 75.20 ± 4.84%, while survival rates in other experimental groups ranged from 52.22 ± 4.82% to 59.33 ± 13.57%. However, regarding the survival rate of D-shape larvae, their survival rates were relatively low across all trials. They displayed abnormal embryo development, distorted shape, unnatural swimming, and were smaller than normal (40-50 µm). Moreover, haploid (n=10), diploid (2n=20), triploid (3n=30), tetraploid (4n=40), and aneuploid were observed in all trials, while only diploid (2n=20) could be discovered in the control group. However, gynogenesis in this tropical oyster is still limited at this time. Therefore, suitable conditions for inducing gynogenesis in oysters should be further developed.