A cell-free system based upon the egg extracts from gynogenetic gibel carp (Carassius auratus gibelio)or bisexual red common carp (Cyprinus carpio red variety) was developed to investigate developmentalbehaviors of the demembranated sperm nuclei. Both red common carp and gibel carp sperm nuclei coulddecondense fully and form pronuclei in the red common carp egg extracts. Gibel carp sperm nuclei couldalso decondense fully and form pronuclei in the gibel carp egg extracts, but red common carp sperm nucleicould not decondense sufficiently in the same extracts. The significant differences of morphological changeswere further confirmed by ultrastructural observation of transmission electron microscopy. The data furtheroffer cytological evidence for gonochoristic reproduction in the gynogenetically reproducing gibel carp. Inaddition, the sperm nuclei in vitro decondensation is dependent on the pH in the extracts, and the decon-densed efficiency is optimal at pH 7. However, no DNA replication was observed in the two kinds of eggextracts during the incubation period of the sperm nuclei. It is suggested that the egg extracts preparedfrom the gynogenetic gibel carp should be a valid in vitro system for studying molecular mechanism ongynogenesis and reproduction mode diversity in fish.
CHANG JIAN LI,JIAN FANG GUIState. Key Laboratory of Freshwater Ecology and Biotechnology,Wuhan Center for Developmental Biology,Institute of Hydrobiology,Chinese Academy of Sciences,Wuhan 430072,China
