Axis determination in polyspermic Xenopus laevis eggs.
Polyspermic Xenopus laevis eggs can be identified easily because of regions of pigment accumulation and white stripes, which arise by a nocodazole-sensitive process. Eggs containing up to four sperm are capable of forming a single embryonic axis. Dispermic eggs display two regions of pigment accumulation, one around each sperm entry point (SEP), and one white stripe between the SEPs. Such eggs with a 180 degree separation between the SEPs were bisected before first cleavage along the white stripe, creating dorsal and ventral halves in many cases. Each half cleaved and formed a tadpole. When eggs were bisected early in the period of cytoplasmic reorganization (0.5-0.6 normalized time), each half could form a complete tadpole. When eggs were bisected after the period of reorganization (0.8-0.9), often one half formed a tadpole with a complete head but reduced or absent tail and the other half formed a tadpole with a complete tail but reduced or absent head. These results demonstrate that sperm cooperate to give a single embryonic axis in polyspermic eggs and the development of dorsal and ventral egg halves differs after egg reorganization before first cleavage.
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D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D005260:Female; D005306:Fertilization; D008297:Male; D010060:Ovulation / Q000187:drug effects; D010063:Ovum / Q000166:cytology; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000166:cytology; D013737:Testis / Q000502:physiology; D014981:Xenopus
D006063:Chorionic Gonadotropin