Gynogenesis in northern pike: UV-inactivation of spermatozoa and the heat shock inducing meiotic diploidization

Gynogenetic northern pike (Esox lucius L.) were produced using UV irradiated sperm and heat shock applied to inseminated eggs shortly after gamete activation. Milt was diluted in immobilizing solution (1:9) and UV irradiated (6.4 W*m-2) for 2-20 min, with dosage in the range of 768-7680 J*m-2. Genetic inactivation of spermatozoa was most efficient when milt was irradiated for 8 min (3072 J*m-2). Insemination of eggs with irradiated milt yielded 100% haploid larvae with hatching rate at 72.1۪.8% (mean±SD), expressed as a percentage of inseminated eggs. Haploid embryo developed and most of them hatched (showing "haploid syndrome") but all haploid larvae died within 48 hours after hatching. After insemination with irradiated sperm the eggs were exposed to a thermal shock of 34°C or 34.5°C, lasting 3 or 5 min, applied 11-16 min after gamete activation. The efficiency of heat shock and survival in experimental groups significantly depended on the source (individual female effect) and quality of eggs. The time of application and duration of the heat shock also affected the survival of embryo and percentage of gynogenetic larvae. Gynogenetic larvae were obtained in all experimental groups with hatching rate as high as 24.2ۭ.6%.