Induction of triploidy in grass carp Ctenopharyngodon idella Valenciennes, ۱۸۴۴: Comparison of cold & heat shocks

Triploidy in grass carp, Ctenopharyngodon idella Valenciennes, ۱۸۴۴, was induced on fertilized eggs to compare cold and heat shocks. Two simplified methods explained for verification of triploidy in grass carp. The cold shock (۷ ?C) was given in three treatments for ۳۰ min starting ۲.۰, ۲.۵ and ۴.۰ min after fertilization. In cold shock, the start point (۲.۰ min after fertilization) showed the highest rate of triploidy (۶۰.۹%). Heat shocks were given at ۳۸ ?C, ۴۰ ?C and ۴۲ ?C, at ۴.۰ min after fertilization and lasted for ۱.۰ min. Produced larvae using heat shock ۳۸ ?C showed ۱۰.۸% triploidy, but no signs of triploidy were seen in other heat shock treatments. Verification of triploidy in grass carp was carried out using karyotyping and measurment of erythrocytes surface area and volume in fingerlings. Ratio of erythrocytes dimention and the size of their nuclei in triploids to diploids was ۲.۳۵ and ۱.۸۰, respectively. Comparison of results obtained from the application of cold and heat shocks indicated that cold shocks are more effective than heat shocks in the induction of triploidy in grass carp.

Keywords:

cold shocks , heat shocks , Grass carp , triploidy