Erythropoiesis and haemoglobin ontogeny in the turtle Emys orbicularis L

The erythropoietic sites and developmental patterns of haemoglobins have been investigated during ontogeny of Emys orbicularis. The yolk-sac blood islands seem to be the unique erythropoietic site during most of embryonic life. Bone marrow haemopoiesis is first observed in young turtles aged one year. The cortical haemopoietic layer of the liver appears involved mainly in granulopoiesis. There is no morphologically well-defined series of primitive or definitive erythrocytes. Rather there is a gradual shift in size from a mean length of 17.4 micrometer in embryos to 19.9 micrometer in the adult. However the size of erythrocytes is highly variable at all stages. Three haemoglobins of adult type and three haemoglobins of embryonic type have been identified by electrophoretic separation. It seems that one haemoglobin is synthesized during the whole life. Embryonic haemoglobins persist for more than a year after hatching while the typically adult haemoglobins appear shortly before hatching.