The hematology of captive Bobtail lizards (Tiliqua rugosa): blood counts, light microscopy, cytochemistry, and ultrastructure

Introduction: Bobtail lizards (Tiliqua rugosa) are native to Australia. The only previous study on the hematology of this species documented just 6 animals. Objectives: The aims of this study were to characterize the light microscopy, ultrastructure and cytochemistry of blood cells, and evaluate CBCs of captive Bobtail lizards. Methods: Over 2 consecutive summers, heparinized venous blood was collected from the ventral coccygeal vein of 46 clinically healthy, captive indoor- or outdoor-housed adult Bobtails. Complete blood cell counts and smear evaluations were performed, and cytochemical stains and transmission electron microscopy were used to further characterize blood cells. Results: The eosinophils of this species were uniformly vacuolated: a unique feature not previously reported in reptiles. Heterophils were the predominant leukocyte, with fewer lymphocytes, azurophilic and nonazurophilic monocytes, occasional eosinophils, and basophils. Thrombocytes were frequently clumped. Slight polychromasia (0–15% of erythrocytes) was typically present. Hemogregarine parasites were seen on some smears. The range of CBC results was often wide. The PCV ranged from 11% to 38%. Total plasma proteins by refractometry were between 3.5 and 7.8 g/dL. Hemoglobin ranged between 2.6 and 12.6 g/dL by the modified hemoglobin-hydroxylamine method. Manual RBC count was 0.35–1.27 × 106/μL, and WBC count was 2.86–22.66 × 103/μL. Bobtail lizards housed outdoors had lower PCVs than indoor-housed animals. Bobtails with hemogregarine infections had lower PCVs than noninfected lizards. Conclusions: Ranges for CBC data were often very wide, influenced by preanalytic and analytic factors. Hemogregarine infection is associated with a decreased PCV, suggesting that some hemogregarine species are pathogenic in this population.