INDUCED MEIOTIC GYNOGENESIS OF PADDLEFISH POLYODON SPATHULA

Viable, diploid gynogenetic (gynogenotes) paddlefish Polyodon spathula were produced by activating eggs with ultraviolet-irradiated shovelno se sturgeon Scaphirhynchus platorynchus spermatozoa and heat shocking. Without irradiation treatment, sturgeon spermatozoa appeared to activ ate the eggs (up to gastrulation), but did not result in any viable hy brids. Experiment 1 determined that heat-shock treatment of 35 C for a 2-min duration within the interval of 2-22 min post-activation result ed in highest yield of gynogenotes (12-19%) from eggs incubated at 18 C. Experiment 2 applied the heat shock treatment at 35 C from 14.0 to 28.0 min in 2-min intervals after activation at 18 C for a larger scal e of gynogenetic production. Both experiments showed that the best yie lds of gynogenotes were obtained when the heat shock treatment occurre d at 16, 18, and 20 min after activation. When these times were expres sed in terms of tau(0) units (duration of one mitotic cycle of synchro nous cell division related to water temperatures), optimal activations were 0.26, 0.29, and 0.32 tau(0) (tau(0) @ 18 C = 63.5 min). Experime nt 3 tested the utility of tau(0) at two different pre shock incubatio n water temperatures of 18 C and 16 C, and determined that there was n o significant interaction in percentage of viable gynogenotes between two different incubation temperatures and the mitotic intervals (0.21, 0.26, 0.31, 0.36, 0.41 tau(0)) tested. Best survival of gynogenotes o ccurred when eggs held at either pre-shock incubation water temperatur es mere shocked at 0.26 tau(0). All gynogenotes examined were histolog ically confirmed to have ovarian tissue and were determined to have si milar oocyte development to that of normal female (control) paddlefish .