The giant panda (Ailuropoda melanoleuca) is a vulnerable species and a charismatic, prominent member of zoological collections worldwide. Despite its importance, few studies have been conducted to determine the hematologic reference of this species,1,2 and no studies to date have been performed to describe normal cell morphology or constituents, achieved by traditional techniques such as cytochemical staining and evaluation of ultrastructural features3-5. The objective of this study was to characterize giant panda leukocytes using a routine modified Wright’s stain, eight cytochemical stains, and transmission electron microscopy (TEM) to further the understanding of accurate cell identification and cytoplasmic contents. Voluntary venipuncture was performed on four healthy individual animals (two adults and two juveniles). Blood was collected from the cephalic vein into calcium ethylenediaminetetraacetic acid (Ca2+ EDTA) for routine and cytochemical stains, and into 2.5% glutaraldehyde preservative for TEM. On routinely stained blood smears, leukocytes could be differentiated into granulocytes (neutrophils, eosinophils, and basophils) and mononuclear cells (lymphocytes and monocytes). Cytochemical staining revealed similar leukocyte staining patterns to that seen in other mammals, with some species differences. On TEM, leukocytes with nuclear and cytoplasmic features of mononuclear cells (e.g., lymphocytes and monocytes) were differentiated from granulocytes, which had a lobulated nucleus and cytoplasmic granules of different electron densities. This study provides novel information on giant panda morphology and cellular constituents and will be clinically applicable for the establishment of hematologic reference intervals, as well as provide a baseline for understanding leukocyte changes in response to disease.
The authors thank Zoo Atlanta for funding this research project and the animal care staff working with the giant pandas at Zoo Atlanta.
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