Scanning cytophotometry of carp, Cyprinm carpio L., erythrocyte populations: the influence of short‐term hypoxic environment and the recovery period following severe bleeding

Scanning stage absorbance cytophotometry was used to examine haemoglobin contents in individual cells or carp erythrocyte populations. Changes in frequency distributional profiles in response to respiratory stress caused experimentally by hypoxia and/or bleeding were studied at intervals. Histograms were drawn of haemoglobin contents of individual red blood cells in populations obtained from the same carp on four consecutive days after the fish was temporarily exposed to hypoxic environment. The modes and means of the haemoglobin values increased during the 3 days following to the stimulus, whereas a decline was measured on the 4th day. Erythrocyte counts showed the total number of red blood cells to be approximately constant during the period of investigation. On the basis of these findings, it is concluded that the mature, nucleated red blood cells of carp are capable of resuming haemoglobin synthesis after stimuli such as reducing ambient oxygen concentration. Frequency distributional profiles covering a period of 4 weeks following severe loss of blood showed that it took 10–12 days after bleeding until masses of immature erythrocytes appeared in the peripheral blood and that there were then two distinct populations of red blood cells. In the course of about 2 weeks the precursor cells developed into mature erythrocytes.