Effects of triploidy on the Caspian salmon Salmo trutta caspius haematology

The aim of this study was a comparison of key haematological features of diploid (2n) and triploid (3n) Caspian salmon (Salmo trutta caspius). Morphometric indices of erythrocytes were determined on blood smears by light microscopy. Triploidy significantly (P < 0.001) increased all morphometric indices measured in the erythrocytes including cell size, cell surface area, and cell volume. The increase in cell size was larger for the major (27%) axis than for the minor (22%) axis, thus making erythrocytes of 3n Caspian salmon more ellipsoidal. The estimated increase in erythrocyte nuclear volume (87%) was bigger than the theoretical expected 50% increase. Haematological indices were measured manually by hemocytometry. Triploids had lower numbers of red blood cells (RBC: 1,120,000 cells/ mL in 2n vs. 700,000 cells/ mL in 3n; P < 0.001) but they were larger in size ( mean erythrocytic volume [MEV]: 363.1 nm(3) in 2n vs. 483.3 nm(3) in 3n; P < 0.001). The decrease in RBC number was not compensated by the increase in MEV and, thus, triploidy affected the haematocrit (Hct: 38.8% in 2n vs. 33.06% in 3n; P < 0.05). Total blood hemoglobin concentration was lower in triploid fish (Hb: 9.9 g/ dL in 2n vs. 8.9 g/ dL in 3n; P < 0.05). In contrast, mean erythrocytic hemoglobin (MEH: 95 mu g in 2n vs. 133.2 mu g in 3n; P\ 0.001) was higher for 3n Caspian salmon as a result of their larger erythrocytes, although MEH concentration ( MEHC: 0.26 g/ dL in 2n vs. 0.27 g/ dL in 3n) did not significantly differ (P > 0.05). White blood cell (WBC) counts (lymphocytes and neutrophiles) were measured and WBC/ RBC ratios were calculated. There were no significant differences in WBC (15,710 cells/ mL in 2n vs. 12,683 cells/ mL in 3n; P > 0.05), lymphocytes, and neutrophils as % WBC as well as WBC/ RBC ratios between two ploidy levels (P > 0.05). Triploid Caspian salmon showed higher erythrocyte abnormalities such as 'twisted', 'tailed', and 'anucleated' cells as well as high portions of immature RBC in blood smears in comparison with diploids (P < 0.001).