Hatching rates and percentage of hatched tetraploid larvae of Siberian sturgeon relative to the timing of the heat shock. Eggs were immersed in a water bath at 37°C for 2 min. (duration of 1 mitotic cycle during the period of synchronous cleavage division [τo] is approximately 59 min at a cultivation temperature of 16°C according to Gisbert and Williot ). The data from groups treated with heat shock for 3 min are not presented. Data with the same superscript (a–dLatin for hatching rate and α,β,γ,δGreek for percentage of tetraploid larvae) did not differ significantly at P < 0.05.