Morphology of red blood cells in tetraploid rainbow trout, Oncorhynchus mykiss larvae

The aim of this study was to evaluate some red blood cell abnormalities in diploid and tetraploid rainbow trout. Tetraploidy induction was done using heat shock 28°C for 10 min، starting at 65 degree-hour post fertilization on fertilized eggs from Iranian brood stock. Eggs from the same lot، without heatshock treatment were selected as control (diploid) group. Ploidy status was verified using red blood cell dimensions as well as the number of nucleular organizing regions in the cell. The results showed that tetraploidy increased all red blood cell dimensions in comparison to diploids (P<0. 05). Red blood cell abnormalities were significantly higher in tetraploids compared to diploids (P<0. 05). The most frequent cell abnormalities were segmentation of the nucleus، 8. 2%; amitosis، 4. 1%; immature cell 3. 8% and cell with incomplete membrane about 1%. The imbalanced increase in red blood cell dimensions plus significant elevation in cell abnormalities would affect the tetraploid fish welfare and fitness in comparison to diploids.