Thermal induction of diploid gynogenesis and triploidy in the eggs of the rainbow trout (Salmo gairdneri Richardson).

Sporadic diploid gynogenetic fry resulted from fertilization with gamma-irradiated sperm. Their frequency increased appreciably when thermal shock treatments, beginning during the first hour of development (--0.4 degrees C lasting 6 hrs 45 min; 26-30 degrees C lasting 10 min), were used. When the eggs were fertilized with normal sperm, a good triploidization rate was induced by means of heat shocks (27-30 degrees C lasting 10 min). It is supposed that the retention of the second polar body caused the gynogenetic diploidy observed.