INDUCED DIPLOID GYNOGENESIS AND POLYPLOIDY IN ORNAMENTAL (KOI) CARP, CYPRINUS-CARPIO L .2. TIMING OF HEAT-SHOCK DURING THE 1ST CLEAVAGE

Experiments on timing of heat shock during the first cleavage in order to optimize induced diploidization of the chromosome set were conduct ed on ornamental (koi) carp, Cyprinus carpio L. The effect of heat sho ck on embryo survival and ploidy level was monitored in gynogenetic of fspring and regular ones. Dimensionless measure of embryological age t au0 was used to express the time of heat shock application. The heat s hock was initiated within the limits of 0.6-3.0 tau0 (0.9-2.0 tau0 in most experiments) after insemination. Incubation temperature prior to treatment was either 25-degrees-C or 20-degrees-C. Water temperature o f heat shock was 39.3-40.5-degrees-C, and duration 2-3 min, in differe nt experiments. Embryo survival is characterized by alternating ''sens itive'' and ''non-sensitive'' periods with lowest survival when heat s hock initiation corresponds to 1.6-1.8 tau0. The highest frequency of 2n mitotic gynogenetic embryos (up to 15% relative to total number of inseminated eggs) was observed when heat shock was initiated at 1.5-1. 6 tau0.