INDUCED DIPLOID GYNOGENESIS IN WHITE BASS

Optimal conditions were determined for induction of meiotic diploid gy nogenesis in white bass Morone chrysops. In two series of experiments, ultraviolet light (UV) irradiation doses to inactivate sperm genome a nd optimal temperature shock to restore diploidy were established. Egg s of white bass were inseminated with sperm from striped bass M. saxat ilis, diluted (1:30) in saline and irradiated with UV at doses ranging from 50 to 1,200 J/m(2). A typical ''Hertwig effect'' was observed wi th increasing UV dose. Larvae obtained at doses of 400 J/m(2) and grea ter were abnormally developed (haploid syndrome) and had a haploid chr omosome number (n = 24). Heat shocks to cause retention of the second polar body were applied. Heat shocks of 2-min duration at 36 degrees C , 38 degrees C, or 40 degrees C were applied at 2 or 3 min after insem ination to white bass eggs inseminated with irradiated (800 J/m(2)) st riped bass sperm. The best results were obtained after application of 36 degrees C heat shock at 3 min after insemination, which induced a s ignificant increase in yield of diploid gynogens (24-39%, from initial numbers of gynogenetic embryos) and provided relatively high postshoc k embryo survival. The gynogenetic origin of diploids obtained was con firmed by the lack of melanophores in putative gynogens (contrary to p igmented control hybrid larvae).