Determination of Triploidy in Rainbow Trout, Oncorhynchus mykiss using Erythrocyte Measurements

In this study, effects of thermal shock (26°C) on Oncorhynchus mykiss egg at different duration time (5, 10, 15 and 20 min.) to triploid rate was determined. Level of triploid induction for each treatment was evaluated by erythrocyte measurements. For this purpose, the caudal peduncles of 40fry for each group were cut off and blood smears prepared. The cell and nucleus lengths (major and minor axis) of 30 erythrocytes for each individual were determined with the aid of a microscope camera (with ScopImage 9.0®) and using a micrometer. There was considerable variation in major axisof erythrocytes cell and nucleus both within individual fish and among individuals of a given ploidy. In the major axis length of erythrocyte, cell and nucleus of 10, 15, 20 min thermal shocked groups were statistically significant compared to the control groups (p<0.05). The presented study demonstrated that the increases of triploid yields are correlated to length oferythrocyte major axis. In conclusion, the best triploid yield for O. mykiss was at 26°C for 15 min initiated 15 min after fertilization.