Cytological observations on fertilization of Scapharca broughtonii from China and Korea

Abstract:

This paper mainly reports on the study on hybridization (K♀×C♂) of two different geographic populations of Scapharca broughtonii from Korea (K) and China (C). Microscopic observations on the fertilization and early embryonic development stained by fluorescent dyes Hoechst 33258 were done by fluorescence microscope. The fertility rate and embryonic malformation rate were counted respectively. The result showed that the sperm could smoothly enter the eggs and activate meiotic division, then the male and female pronucleus formed after two polar body were released in succession. The two pronuclei then moved to each other to fuse into the zygote, which subsequently started the mitosis and early embryonic development. Most embryos developed into D-larvae successfully. The fertility rate and embryonic malformation rate were 92% and 23.5% respectively. The relative high malformation rate was probably attributed to polyspermy which disrupted chromosome separation.