Abstract
Stingrays are well-represented members of the marine environment and are important animals in the exhibits of many aquariums and zoological parks throughout the world. At present, there are few published normal values for their blood chemistries and hematology. Some blood chemistry reference intervals have been established for elasmobranchs, and most of these deal with sharks.1,2 Establishing clinical pathological reference intervals for stingrays can help enhance medical care in captivity and health assessments in wild populations.
Southern stingrays (Dasyatis americana) were caught in the bottom trawl nets of three fishery independent boats operated by the SC Department of Natural Resources during June and July 2002. Moving north to south: two boats sampled from Winyah Bay, SC to St. Catherine's Sound, GA, and a third boat sampled from St. Catherine's Sound, GA to St. Augustine, FL. Once on deck, the rays were measured, weighed, bled via cardiac puncture, and immediately returned to the water. Values measured on board included packed cell volume (PCV) and total solids (TS). Plasma chemistry analysis was performed at the clinical pathology laboratory at the North Carolina State University College of Veterinary Medicine, on a Roche/Hitachi 912 Clinical Chemistry System (Roche Diagnostics, Indianapolis, Indiana, USA). Osmolality was measured with a freezing point osmometer (Advanced Micro-Osmometer, Model 3MO, Advanced Instruments Inc., Needham Heights, Mass, USA).
The following median values were obtained: PCV, 22 percent; TS, 5.65 g/dL; total protein, 2.6 g/dL; sodium, 315 mmol/L; potassium, 4.95 mmol/L; chloride, 342 mmol/L; calcium, 16.5 mg/dL; phosphorus, 4.7 mg/dL; urea nitrogen, 1243 mg/dL; glucose, 30 mg/dL; aspartate aminotransferase, 14.5 U/L; creatinine phosphokinase, 80.5 U/L; and osmolality, 1065 mOsm/kg. Bicarbonate was less than the low end of the instrument range (5 mmol/L) in all but three samples, all of which registered at 5 mmol/L. Anion gap was negative in all samples. Albumin was less than the low end of the instrument range (1 mmol/L) in all but one sample, which registered at 1.1 g/dL.
Values from stingrays caught in the northern range and the southern range were compared. Sex ratio and size range did not differ between sampling locations. Total solids, glucose, phosphorus, aspartate aminotransferase, creatinine phosphokinase, calcium, total protein, and osmolality were all higher in the southern range. There were no differences in PCV, urea nitrogen, sodium, potassium, or chloride. No differences were detected between males and females, nor did values differ according to size. Total solids and total protein values were linearly related (R2 = 0.91) and the equation for the fitted line was TS = (1.161xTP) + 2.54.
The differences in clinical pathological values between the northern and southern ranges may reflect differences in oceanographic features, water chemistry, food supply, or sampling. Although trawl capture likely exerts an influence on the clinical pathology values, capture or restraint of some kind is used in almost all blood sampling of aquatic fishes. The reference ranges reported here can be used to aid in the management of aquarium stingrays and to create a baseline for health monitoring of the wild Dasyatis spp.
Acknowledgements
This work was supported by a grant from the North Carolina State University College of Veterinary Medicine and the South Carolina Dept. of Natural Resources. The authors would like to thank Dr. Dave Rotstein, Dr. Michael Stoskopf, Sid Ballantyne, the staff of the NCSU CVM clinical pathology laboratory, Dr. Greg Lewbart, Michael Arendt, Dr. Maria Correa, and the crews of the R/V Lady Lisa, F/V Miss Tina, and R/V Georgia Bulldog.
References
1. Harms C, Ross T, Segars A. 2002. Plasma biochemistry of bonnethead sharks. Veterinary Clinical Pathology. 31:111-115.
2. Stoskopf MK. 2000. Normal hematology of elasmobranches. In: Feldman, B., Zinki, J., and N. Jain (eds.). Veterinary Hematology. Lippincott Williams & Wilkins., Philadelphia., Pp. 1174-1178.