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Hematologic reference intervals for koi (Cyprinus carpio), including blood cell morphology, cytochemistry, and ultrastructure.

BACKGROUND
Hematologic data are used routinely in the health care of humans and domestic mammals. Similar data for fish are largely fragmentary or have not been collected.


OBJECTIVES
The primary purpose of this study was to determine hematologic reference intervals for koi, an ornamental strain of the common carp (Cyprinus carpio). Secondarily, the morphology, cytochemical reactions, and ultrastructure of koi blood cells were characterized.


METHODS
A CBC was performed manually on heparin-anticoagulated blood specimens using Natt and Herrick's diluent and a Neubauer-ruled hemacytometer. Leukocyte differential counts were done on Wright-Leishman- and Diff-Quik-stained blood smears. Cytochemical reactions of koi leukocytes were determined using commercial kits. Transmission electron microscopy was performed to characterize the ultrastructural features of koi blood cells.


RESULTS
Hematologic reference intervals were established for healthy koi for PCV (30-34%), hemoglobin concentration (6.3-7.6 g/dL), RBC count (1.7-1.9 X 10(6)/ microL), WBC count (19.8-28.1 X 10(3)/ microL), RBC indices, and differential leukocyte counts. Lymphocytes were the predominant leukocyte (accounting for up to 80% of all leukocytes), whereas eosinophils were rare. Basophils were positive with PAS staining. Naphthol AS-D chloroacetate esterase activity was observed only in eosinophils. alpha-Naphthyl butyrate esterase and beta-glucuronidase activities were positive in monocytes. Some lymphocytes were reactive for alpha-naphthyl butyrate esterase and acid phosphatase activity. Ultrastructurally, leukocytes, erythrocytes, and thrombocytes were identified on the basis of cytoplasmic organelles and granule appearance.


CONCLUSION
Hematologic reference intervals and knowledge of the cytochemical reactions and ultrastructural characteristics of koi leukocytes will help standardize hematologic studies in this species.