Induced meiotic gynogenesis in shovelnose sturgeon

Gynogenesis was induced in three shovelnose sturgeon (Scaphirhynchus platorynchus) by heat shock after egg activation with UV-treated paddlefish (Polyodon spathula) milt. Ultraviolet dosage (J m(-2)) for the pooled milt samples was calculated using the following linear regression equation: Dosage = 2405.27 - 352.80X + 19.78X(2) (X = percent transmittance of milt). Activated 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 highest 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 viable 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 in the control fertilization of sturgeon eggs with intact paddlefish sperm which verified the gynogenetic origin of the offspring produced.