Erythropoiesis in the diploid and tetraploid Odontophrynus americanus: An evolutionary approach in these cryptic species (Amphibia, Anura, Leptodactylidae)

Polyploidy is one of Nature's strategies to create diversity among fauna an d flora, resulting in new species. We have used light, scanning and transmi ssion electron microscopy to perform morphometric analyses in maturing eryt hroid cells of the cryptic species diploid and tetraploid Odontophrynus ame ricanus frogs. Normal blood of both specimens contained 97%-99% erythrocyte s and 1%-3% reticulocytes, besides thrombocytes and leucocytes. Mature eryt hrocytes were flattened, ellipsoidal, nucleated, with cytoplasm rich in hae moglobin. Five days after being made anaemic, 15% and 33% of diploid and te traploid red blood cells respectively, were in an immature stage, basically proerythroblasts. These cells were also seen at the 10th day, in addition to basophilic and polychromatophilic erythroblasts. By day 15 a higher numb er, 75% and 89% of reticulocytes in earlier maturation stage was found, res pectively. At day 20 of recovery from anaemia, there were 63% and 85% of re ticulocytes, respectively, most in an advanced stage of maturation. The num ber of immature cells then gradually decreased at days 30 and 50. Cytoplasm ic inclusions similar to Heinz bodies were found in these cells associated with RNA or RNP. Morphometric analysis showed that the tetraploid erythroid cells synthesise 30% more ribosomes than the diploid erythroid cells. The density of ribosomes/mu m(2) allowed these cells to be classified into seve n classes: proerythroblasts, basophilic erythroblasts I and II, polychromat ophilic erythroblasts I and II, reticulocytes and erythrocytes. Such morpho metric strategy suggested that gene activity was more intense in the tetrap loid maturing erythroid cells, despite the marked tendency of these tetrapl oid cells towards diploidisation of the genome expression.