Hematology of the sandbar shark, Carcharhinus plumbeus: standardization of complete blood count techniques for elasmobranchs

Abstract

Standardized hematologic methods and reference intervals have not been established for cartilaginous fishes (sharks, skates, and rays) despite the large number of animals displayed in zoos and aquariums worldwide. The focus of this study was to validate CBC methods for sandbar shark (Carcharhinus plumbeus) blood, based on criteria established in human medicine, for the following tests: RBC count, total WBC count, PCV, hemoglobin (Hgb) concentration, and WBC differential percentages. Replicate CBCs were performed using blood samples from 5 captive sandbar sharks. Three protocols for RBC and total WBC counts were compared, as were different centrifugation times for PCV determination, and 2 methods for Hgb concentration. Means, minimum and maximum values, and CVs were compared to CAP and CLIA performance guidelines for human tests. Total WBC counts in a diluent modified for elasmobranch blood, Hgb concentration by the cyanmethemoglobin method after removal of nuclei, and WBC differential percentages showed acceptable performance. PCV results were acceptable when tubes were centrifuged for at least 5 minutes. Total RBC counts by all 3 methods exceeded the acceptable error for manual counts of human cells. Standardized CBC tests can be used as health assessment tools for elasmobranchs. Total RBC counts should be viewed as estimates.