Induction of triploidy and tetraploidy in stinging catfish, Heteropneustes fossilis (Bloch), using heat shock

Induction of triploidy and tetraploidy was attempted in Heteropneustes fossilis using heat shock. The optimal age of zygote, temperature level and duration of thermal shock required for effective induction of triploidy and tetraploidy was investigated in a series of experiments. A maximum of 82+-7% triploids (3n=87) were obtained when fertilized eggs (2.5-min old) were heat shocked at 40(degree)C for 4-min duration. A maximum of 40+-8% tetraploids (4n=116) was obtained when the fertilized eggs (30-min old) were heat shocked at 40(degree)C for 4-min duration. The triploid and tetraploid red blood cells (RBCs) nucleus volumes were 1.4 and 2.1 times greater, respectively, than that of the diploid RBC nucleus.