INDUCTION OF ENDOMITOTIC GYNOGENESIS IN THE NISHIKI-GOI, JAPANESE ORNAMENTAL CARP

Endomitotic gynogenesis was induced in batches of eggs obtained from J apanese ornamental carp, nishiki-goi, by exposing the eggs, activated with saline-diluted (1:9) UV-irradiated (500-800 J/m2) common carp spe rm, to heat shock (38.0-degrees-41.0-degrees +/- 0.5-degrees-C for 1.5 or 2 min). The wild-type color of the common carp, dominant over the known koi colorations, served as a marker to monitor the induction of gynogenesis. Heat shocks were applied at various biological ages, dete rmined by a dimensionless factor termed tau-o. Typical normal survival curves were produced in all experiments. The highest survival rates ( 20%-40%) were observed in 24 and 48-hour-old embryos shocked at 1.2 to 1.4-tau-o, and the lowest survival rates at the age of 1.0-tau-o and above 1.6-tau-o. Survival of embryos increased again to approximately 40% in eggs exposed to thermal shock at the age of 2.3-2.4-tau-o, in e ggs presumably shocked before the second mitotic cleavage. Shocking tw o large batches of eggs at 1.3-tau-o and 1.6-tau-o resulted in surviva l rates of 55.4% and 27.1%, respectively. The use of endomitotic gynog enesis in order to produce clones with desired color patterns is discu ssed.