Abstract

There are few literature references for hematology values or white blood cell morphology descriptions for Amazon freshwater stingrays (Potamotrygon spp.). Data for these parameters from healthy animals are important to establish baseline values. Complete blood counts were performed on two species, P. leopoldi and P. henlei; six newly acquired, wild-caught and six long-term captive rays. Rays were sedated with buffered tricaine methanesulfonate at 75-100 ppm. Dive gloves and a PVC pipe placed over the tail were used to prevent contact with the venomous spines. Blood was collected from the caudal tail vein using a 3-ml syringe with an 18-23-ga needle, depending on size of the animal. Samples were immediately placed into 1.8-ml, dry heparin microtubes. Manual determination of total leukocyte count (WBC) was performed using the Avian Leukopet^TM kit (Vetlab Supply, Inc., Miami, Florida) following package directions. Hematocrit (HCT) was measured by micro-centrifugation and total solids (TS) by refractometer. Blood smears were stained with Dip Quick (Jorgensen Laboratories, Inc., Loveland, Colorado). The white blood cell morphologies of both groups and all individual rays were not obviously different in appearance. Cell identification was based on morphology and nomenclature previously established for the sandbar shark (Carcharhinus plumbeus).¹ Statistical analysis with an independent t-test found a significant difference between the two groups for WBC, HCT, and TS. The WBC was greater in newly acquired animals. The HCT and TS were found to be greater in long-term captive animals. Data collection from a larger sample size is recommended to further delineate differences.

Acknowledgements

The authors would like to thank Shelley Halach, CVT, Erica Clayton, Collections Manager and Dr. Trevor Zachariah for their help with this project.

Reference

1.  Arnold JE. 2005. Hematology of the sandbar shark, Carcharhinus plumbeus: standardization of complete blood count techniques for elasmobranchs. Vet Clin Path 34(2): 115-123.