Osmotic Fragility and Erythrocyte Size in Iguana iguana (Sauria - Iguanidae) in Captivity

The erythrocyte size and osmotic fragility were studied in blood samples from adult (n= 40) and juvenile (n= 40) specimens of Iguana iguana. In fresh preparations the erythrocytes were large, oval cells. The largest diameters were 17.06 ± 2.5 mm (juvenile) and 16.20 ± 1.25 mm (adults), and the smallest diameters were 8.23 ± 1.87 mm (juvenile) and 9.00 ± 1.00 mm (adults). In fixed and stained preparations, the largest erythrocyte diameters were 15.28 ± 3.3 mm (juvenile) and 15.51 ± 1.3 mm (adults), and the smallest were 7.82 ± 0.65 mm (juvenile) and 7.85 ± 0.8 mm (adults). The haematocrit value for both juvenile and adult specimens was 27 ± 2%; the red blood cell counts were 1.3 ± 0.43×10^sup 12^/l (juvenile) and 1.2 ± 0.35×10^sup 12^/l (adults). Although no significant differences were observed in the cumulative osmotic curves, the derivative curve of adult specimens indicates the presence of at least two erythrocyte populations with osmotic fragilities at about 70 and 60 mm NaCI, representing 27% and 73% of the total cells, respectively. In samples from juvenile specimens, a major peak at about 70 mm NaCI was observed, which represented 85% of the total cell population. The difference in osmotic resistance between these erythrocyte subpopulations is correlated with their respective geometrical parameters, and compared to that of erythrocytes from other vertebrates.[PUBLICATION ABSTRACT]