RED CELL MORPHOMETRICS AND VOLUME IN THE CICHLID TELEOST TILAPIA MOSSAMBICA, USING A CHROMIUM-51 LABELING METHOD

¹ Department of Zoology, University of Hawaii, Honolulu, Hawaii

1. Erythrocytes, small and large lymphocytes, macrophages and thrombocytes were identified. No granulocytes were found in stained or living preparations. Hematocrits averaged 25.8 ± 4.6% for caudal vessel samples and 23.0 ± 3.8% for ventral aorta samples. Red cell counts were 1,549,000 ± 73,000 SD per mm³. Red cells were 11 ± 0.7 long, 7.5 ± 0.1 µ wide and 3 µ thick.

2. A technique is described for cannulation of the ventral aorta to allow repetitive sampling or injection while the fish is restrained or confined.

3. The labeling of erythrocytes with ⁵¹Cr followed a linear curve with maximum cell incorporation occurring at approximately 90 minutes post-labeling.

4. A long period of slow mixing was noted for injected ⁵¹Cr-RBCs after an initial dilution phase of 10 to 60 minutes. The total average total volume of red cells obtained for Tilapia as determined by ⁵¹Cr dilution was 0.65 ± 0.14 ml./100 g. body weight and the mean total blood volume was 3.17 ± 0.48 ml./100 g. body weight. There was an allometric relationship suggested between TBV as a percentage of body weight and weight. Higher proportional volumes were associated with lighter animals.