Hematology, Blood Biochemistry and Cytochemical Characteristics of Blood Cells of Captive Aldabra giant tortoise (Aldabrachelys gigantea) in Thailand

Aldabra giant tortoises (Aldabrachelys gigantea), well-known pet tortoises worldwide, were classified as Appendix II by The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This study aims to investigate the hematological, blood biochemical, and cytochemical characteristics of blood cells in healthy Aldabra giant tortoises in captivity. Blood samples were collected from the dorsal tail vein of 12 tortoises (6 males and 6 females) during May and October 2022. The hematological values showed no statistically significant differences between male and female tortoises. However, in female tortoises, calcium and phosphorus levels were significantly higher than in male tortoises (P<0.05). Conversely, uric acid levels in males were significantly higher than in females (P<0.05). The staining techniques employed included Wright-Giemsa, Sudan Black B, Acid Phosphatase, Alkaline Phosphatase, Periodic Acid Schiff, and Peroxidase staining. Wright-Giemsa staining is the most suitable stain for basic hematology and differential counts. The morphology of red blood cells was characterized by oval cells with round or oval concentric nuclei. The white blood cells were classified into five categories: heterophils, eosinophils, basophils, lymphocytes, monocytes or azurophils, and thrombocytes. Each type of white blood cell exhibited different staining results, depending on their characteristic or physiological properties. The results of this study can be instrumental for future health care, research in veterinary medicine, and the conservation of Aldabra giant tortoises.