DNA-REPLICATION CYCLE IN PARTHENOGENETICALLY DEVELOPING EGGS OF THE STARFISH ASTERINA-PECTINIFERA

Starfish oocytes artificially activated by a calcium ionophore will de velop normally if the formation of polar bodies is suppressed. In the present paper, schedules of the DNA replication period (S phase) of th ese parthenogenotes were explicitly timed using 5-bromo-2'-deoxyuridin e (BrdU) and anti-BrdU monoclonal antibody. Their schedule of S phase was identical to that of fertilized eggs. Consequently an S phase regu lation system is triggered even in parthenogenotes raised by dual trea tment of egg activation and polar body suppression. The S phase schedu le of parthenogenotes confirms the temporal pattern of chromosome dupl ication, observed by other researchers, leading to tetraploid partheno genotes. The S phase determination also provides a basis for argument concerning the number of centrioles participating in parthenogenetic d evelopment. If polar body formation of activated eggs was not suppress ed, the first S phase was normal, but the second S phase did not recur on time. A rigidly regulated system of DNA replication cycle, which s hould be an essential prerequisite for parthenogenesis, thus requires the content of polar bodies.