Hemoglobin switching in the salamanderPleurodeles waltlii

Summary In order to study the cellular distribution of larval and adult hemoglobins during larval development ofPleurodeles waltlii a double specific immunofluorescent labelling technique was developed.Rabbit antibodies specific for larval and adult hemoglobin components were prepared and conjugated with tetramethyl-rhodamine isothiocyanate for the anti-larval antibodies and fluorescein isothiocyanate for the anti-adult hemoglobin antibodies.Both simultaneous and sequential staining with the two types of fluorescent antibodies indicated that larval and adult hemoglobins were never observed within the same erythrocyte during development. The results provide evidence that two distinct cell populations exist, one synthesizing exclusively larval hemoglobins which is progressively replaced by the other one synthesizing exclusively adult hemoglobins. It remains to be determined if these two populations arise from two distinct types of stem cells (adult and larval) or from the same stem cell type.