Erythropoiesis through clone cell formation in peripheral blood of the white sucker, Catostomus commersoni, studied after labeling with 3H-thymidine for various exposure intervals

A process of erythropoiesis, in which new red blood cells (clone cells) originate from preexisting young mature red blood cells as sac-like protuberations or nuclear blebs in the peripheral blood of the white sucker, is demonstrated. These protuberations, called the clone cells, which became labeled on exposure to 3H-thymidine and which stain positively for deoxyribonucleic acid (DNA), eventually condense, producing margins of cytoplasm which surround discrete nuclei. This cytoplasm is shown to contain ribonucleic acid (RNA) and, later, the appearance of hemoglobin can be demonstrated with the acridine orange fluorescence method. Clone cells make up about 10% of the cells of the peripheral blood of the white sucker. Both clone cells and their mother cells became labeled on exposure to 3H-thymidine: from 25% to 38% of the young mature red blood cells had mean grain counts which varied from 18.2 to 21.1 grains per cell; from 13.1% to 18.3% of the stage II clone cells gave mean grain counts of 235 to 301 grains per cell. Greatest uptake of 3H-thymidine was observed about the 48th h and the fifth day. This investigation shows that clone cell formation, in the peripheral blood of teleost fish, is identical with the one demonstrated earlier for birds and for reptiles. This is the first time, however, that grain counts of mother nuclei and clone cell nuclei have been reported and compared to one another.