Effects of sperm irradiation and heat shock on induction of gynogenesis in muskellunge (Esox masquinongy)

We report here the first induction of gynogenesis in esocid fish by UV irradiation and heat shock. Optimal dosage of sperm UV irradiation was in the range of 1440-2160 J/m2. Eggs fertilized with irradiated sperm at such dosages and not heat shocked yielded 100% abnormal larvae with the fertilization rate at 48.3 ± 8.4% (mean ± SD). There were no significant differences in survival to the eyed stage under the heat shock conditions tested (5-30 min post-fertilization for 5-30 min at 26-30°C). Gynogens were induced in most of the groups with hatching rates at 0.2-3.3%. Optimal conditions for gynogenetic induction of muskellunge (Esox masquinongy) were the application of 30°C for 8-10 min beginning 20 min post-fertilization, with a yield of gynogens at 5.8-6.0% (hatched normal larvae/viable eyed-stage embryos). Ploidy was identified by chromosome preparation, silver staining for nucleolar organizer regions, and flow cytometry measurement of the nuclear DNA content using eyed-stage embryos and larvae. Haploids hatched but died within 1 week.Funding for this project was provided by the Federal Aid in Sport Fish Restoration Program (F-69-P, Fish Management in Ohio) administered jointly by the United States Fish and Wildlife Service and the Ohio Division of Wildlife