Why do only mammalian’s erythrocytes have no nucleus? What mechanism does work in enucleation of mammalian’s erythroblasts? These two big questions in the mammalian erythrocytes and erythroblasts still remained. We understand that not only erythropoietin but also HIF (hypoxia-inducible factor) passways are much important to induce hematopoiesis (maturation of the erythrocytes); however, we have not answered the questions at present. Although the structures of membrane and membrane skeleton of human erythrocytes have been studied so well, it is not completely clarified that the nucleated erythrocytes, such as in birds and/or fishes, have similar (or same) structures or not. What differences are there among those membrane structures? Analysis of membrane structure may give us good hints for the big questions. In 2005, an erythrocyte has been identified in the soft tissue of Tyrannosaurus rex. Why did our descent of mammalians survive over the K-Pg extinction event 65.5 million years ago but not T. rex? It is also interesting to discuss this question in the view of evolution of erythrocytes. Relating to this, effect of hypoxia and environmental stress, such as cold shock, on erythropoiesis is also very interesting topic. Now, a lot of studies are performed not only on the erythropoiesis of mammalians but also on the fishes, frogs, and birds. In this issue, we are interested in original research articles as well as reviews that explore aspects of erythropoiesis in vertebrates including mammalians.

Potential topics include, but are not limited to:

• Erythropoiesis of vertebrates including mammalians
• Phylogeny and ontogeny of membrane structure of erythrocytes
• Phylogenetic view of EPO and HIF passway in the hematopoiesis
• Erythrocytes and hemoglobin in invertebrates
• Phylogenetic and ontogenetic view of iron metabolism
• Phylogenetic view of hemoglobin synthesis
• Environmental effects on the erythropoiesis in ectothermy
• Hypothesis of biological significance of enucleation
• Approach to mechanism of enucleation by using iPS cell