Induced gynogenesis in black crappie

This study reports the results of initial experiments on induced diploid gy nogenesis in black crappie Pomoxis nigromacalatus. White bass Morone chryso ps were an effective sperm donor for gynogenetic experiments with black cra ppies. White bass spermatozoa fertilized black crappie eggs, but hybrid lar vae were not viable and died after hatching. In a series of experiments, we determined the ultraviolet (UV) light dose required to inactivate the sper m genome and the heat shock parameters needed to restore diploidy. Black cr appie eggs were inseminated with white bass sperm irradiated with UV dosage s ranging from 25 to 2,500 J/m(2). A typical "Hertwig effect" in the yield of hatched larvae was observed with dosages greater than 100 J/m(2). The ge netic inactivation of paternal chromosomes was confirmed by how cytometry m easurement of DNA content in larval cells. Larvae resulting from sperm irra diated at a dose of 1,000 J/m(2) were haploid. Time durations of mitotic in terval (tau(0)) at different temperatures for black crappies have been dete rmined to standardize data on heat shock timing in experiments with differe nt preshock temperatures. The resultant regression equation (tau(0) = 70.96 -2.32T where T is water temperature) was used for calculation of the value of tau(0) for any water temperature observed in the experiments. Applicatio n of heat shock was effective for suppression of the second meiotic divisio n in eggs and resulted in morphologically normal diploid gynogenetic larvae . The effectiveness of shock was dependent on its parameters. The best yiel d of diploid gynogens (8.3% from the initial number of eggs) was observed a fter application of 37 degrees C shock and 1.5-min duration at 0.05 tau(0) after insemination. Future experiments will be directed to increase the eff ectiveness of heat shock by further optimization of its parameters.