Abstract
Blood samples from 41 Sandbar or Brown sharks, Carcharhinus plumbeus, (25 males, 16 females) were analyzed for white and red blood cell counts, white blood cell differentials, hematocrit and hemoglobin. The sharks were assumed healthy and measured 2 to 5 feet total length. Test methods included Natt-Herrick diluent for hemacytometer cell counts, May Grunwald, Wright-Giemsa stain for white cell differentials, microhematocrit centrifugation for hematocrit, and azide-methemoglobin method for hemoglobin.
There are no standard methods established for elasmobranch hematology and leukocyte nomenclature. This study classified the leukocytes as follows: monocytes, lymphocytes, neutrophils (all resembling the respective mammalian cells), fine eosinophilic granulocytes, coarse eosinophilic granulocytes and granulated or "G4" thrombocytes.4 There is controversy over whether these G4 cells should be considered in the white cell differential or simply represent thrombocytes. It is impossible to differentiate the G4 cells from other leukocytes in the diluent 2 formula by Natt and Herrick.2 An effort was made to simulate the biological condition of these animals by adjusting the osmolality of the diluent to 1000 mosm/kg with urea and sodium chloride. The result was much less cell distortion, greater clarity and ease of cell identification; the G4 cells are distinct and were tallied separately.
The mean and standard deviation were calculated for each parameter; the white cell counts and distributions were calculated with and without G4 cells for comparison. There were no significant sex-related differences in any of the hematologic parameters; the uncharacteristically wide range of hematocrit values will be discussed in relation to methodology. White cell differentials showed in order of prevalence: lymphocytes, G4 cells, fine eosinophilic granulocytes (FEG), coarse eosinophilic granulocytes (CEG), neutrophils, and monocytes. G4 cells were included in the counts because they may be clinically significant as one determinant of health. The Natt-Herrick method, modified for osmolality, should be employed to clearly distinguish these cells. These are the first known hematologic profiles on Sandbar sharks using the modified Natt-Herrick method and should serve as a baseline for health evaluations in this species.
References
1. Mainwazing, G., and A.F. Rowley. 1985. Studies on Granulocyte Heterogeneity in Elasmobranchs. Fish Immunology. Academic Press, New York, Pp. 57-69.
2. Natt, M.P., and C. A. Herrick. 1952. A new blood diluent for counting the erythrocytes and leucocytes of the chicken. Poultry Science 31:735-738.