Triploidy induction in Pacific oyster Crassostrea gigas by caffeine with thermal shock

Zygotes of Pacific oyster (Crassostrea gigas) were treated for triploid induction with caffeine (10 mmol/L, 15mmol/L and 20mmol/L) in combination with thermal shocks (at 40 minute post-fertilization) lasting for 5 and 10 minutes. The highest yield of triploids, 41.5%, was obtained from the treatment with 20 mmol/L caffeine at 34°C lasting 10 minutes. The triploid levels were less than 30.0% in other treatments. Triploid induction was more effective in treatment with 15-20 mmol/L caffeine at 34-38 °C than with lower concentrations of caffeine at temperatures below 32 °C. Our results suggest that triploid induction with caffeine in combination with thermal shocks is less efficient than some other methods reported previously. © 1998 Science Press.