Analysis of gamete compatibility and zygote fertility for Crassostrea angulata and Crassostrea sikamea

To evaluate the gamete compatibility and zygote fertility between Crassostrea angulata and C.sikamea, the fertilization rate and hatching rate of two oysters at different temperature(18, 21, 24, 27 and 30 ℃)and salinity(16, 20, 24, 28 and 32)were studied, and then the F₅₀ critical values were determined under the different sperm concentration.Results clearly demonstrate that hybridization between C.angulata and C.sikamea is achievable in one direction due to asymmetric gamete compatibility.Fertilization and hatching level of SS, AA and SA was raised with temperature increasing, while these max values were severally 99.1?Dd#177;0.3%, 98.4?Dd#177;1.2% and 81.3?Dd#177;2.8% for fertilization rate, and 99.1%±0.5%, 96.8%±2.8% and 67.1%±5.5% for hatching rate at 27 ℃, respectively.Fertilization rate and hatching rate of SS, AA and SA at a salinity of 24 were severally 98.8%±1.3%, 94.8%±4.5%, 81.1%±7.4% and 75.9%±3.7%, 86.4%±4.2%, 66.1%±4.5%, respectively.Fertilization rate and hatching rate of SS, AA and SA at sperm concentration of 10³ ind./μL were severally 92.5%±2.2%, 87.2%±5.7%, 92.4%±1.2%, and 79.8%±4.3%, 78.9%±7.8%, 82.2%±7.0% at temperature of 27 ℃ and a salinity of 24, respectively.The F₅₀ critical values of gamete compatibility and zygote fertility were calculated, and were 58.88 ind./μL and 208.93 ind./μL, respectively.This study provided the theory and practice for reproductive isolation mechanism and interspecific hybridization between C.angulata and C.sikamea.