Efficiency and optimization of heat shock in production of rainbow trout tetraploid

Interploid triploid rainbow trout were produced by mating of female tetraploid and male diploid fish and this method is suitable and economical for sterilization of fish. In order to produce tetraploid fish by heat shock, the most appropriate temperature and shock time were investigated. 6 treatments with three replications including control group (fertilized eggs without heat shock) and fertilized eggs greater than 5 mm in diameter and also those less than 5 mm in diameter with shocks of 1, 5 and 10 minutes after Fertilization was investigated at temperatures 28, 30 and 32 °C, respectively. Determination of tetraploidy was done by comparing the DNA content of red blood cell nuclei in different treatments using flow cytometry. The highest tetraploid levels were observed in temperature of 28 ° C in eggs above 5 mm in diameter and below 5 mm (p>0.05) 19.8% and 11.9%, respectively. Based on the results, temperatures of 28, 30 and 32 ° C were induced tetraploidy in the eggs below 5 mm dimeter, and in those above 5 mm, only 28 and 32 °C induced tetraploidy. The favorite temperature for Induction of tetraploidy in trout is 28 ° C and the appropriate time to initiate shock is 65 hour-degree after fertilization for 7 minutes shocking.