Induced meiotic gynogenesis in shovelnose sturgeon

Gynogenesis was induced in three shovelnose sturgeon (Scaphirhynchus plator ynchus) by heat shock after egg activation with UV-treated paddlefish (Poly odon spathula) milt. Ultraviolet dosage (J m(-2)) for the pooled milt sampl es was calculated using the following linear regression equation: Dosage = 2405.27 - 352.80X + 19.78X(2) (X = percent transmittance of milt). Activate d eggs were incubated at 18 degrees C until shocking at 35 degrees C. Shock duration was applied at 0.05 tau(0) intervals from 0.15 to 0.40 tau(0) (8. 25 to 22.00 min post-fertilization; tau(0) at 18 degrees C = 55 min). The h ighest yield of gynogenotes (16%) was observed at 0.25 tau(0) for female 3, 10 % at 0.30 tau(0) for female 2 and 12% at 0.35 tau(0) for female 1. The percentage of viable gynogenotes responded quadratically to the tau index ( tau(s)/tau(0)) when shock treatments were applied. The higher yields of via ble diploid sturgeon gynogenotes were achieved when eggs were heat shocked at embryological ages ranging from 0.25 to 0.35 tau(0) (approximately 14 to 19 min post-activation at 18 degrees C). No viable hybrids were produced i n the control fertilization of sturgeon eggs with intact paddlefish sperm w hich verified the gynogenetic origin of the offspring produced.