Induced diploid gynogenesis and polyploidy in the ornamental (koi) carp, Cyprinus carpio L. : 4. Comparative study on the effects of high- and low-temperature shocks.

The effects of high- and low-temperature shock treatments, applied at different phases of the 2nd meiotic division within the limits of 0.05-0.60 τ0 (τ0 = relative unit of embryological age) in order to induce gynogenesis in the common carp, were studied. A remarkable difference in the effect of two temperature treatments applied at the same biological age after insemination (expressed in τ0) was revealed. The curves of embryo survival and diploid gynogenetic larva output showed a bimodal response in cold-shocked gynogenetic progenies, with the highest level of diploid larva output at the periods 0.05-0.10 τ0 and 0.30-0.40 τ0 (after insemination), separated by a period of high sensitivity to cold shock (0.15-0.25 τ0). In contrast to this, the curves of embryo survival and diploid gynogenetic larva output showed a single, narrow, peak corresponding to 0.15-0.25 τ0 in heat-shocked gynogenetic progenies. The results obtained are in general accord with those of previous experiments on induced gynogenesis and triploidy in common carp, in which either cold- or heat-shock was used.