Morphologic, cytochemical staining, and ultrastructural characteristics of blood cells from eastern diamondback rattlesnakes (Crotalus adamanteus)

Objective-To evaluate light microscopic, cytochemical, and ultrastructural characteristics of blood cells from eastern diamondback rattlesnakes. Animals-10 healthy snakes. Procedure-Various stains, including Wright-Giemsa, benzidine peroxidase, Sudan black B, chloroacetate esterase, cc-naphthyl butyrate esterase, acid phosphatase, leukocyte alkaline phosphatase, periodic acid-Schiff with diastase, and toluidine blue, were used to stain leukocytes differentially on multiple blood smears. Electron microscopy also was performed. Results-Lymphocytes were the most commonly observed leukocyte and could be distinguished from thrombocytes, using periodic acid-Schiff stain with diastase. Azurophils also were commonly observed; their granules stained with peroxidase. Eosinophils were not identified; however, 2 morphologic variations of heterophils were seen in the blood of ail snakes and were considered the same cell type at different stages of cytoplasmic granule development. Heterophil granules were better preserved, using a one-step Wright-Giemsa method that did not require alcohol fixation prior to staining. Degranulated heterophils were observed in all preparations. Conclusions-Most leukocytes of eastern diamondback rattlesnakes can be identified easily on Wright-Giemsa-stained preparations. However, hematologic stains that do not require alcohol fixing prior to staining may be preferred for leukocyte evaluation in certain reptiles. A limited degree of heterophil maturation may continue in the blood of healthy snakes. This, along with degranulation of heterophils, may result in a Variable staining pattern in this cell type, regardless of the stain used. Clinical Relevance-Results provide baseline data for use in hematologic testing in diagnosis of disease and monitoring of treatment of sick or injured snakes.