Hematology of the Dasyurid Marsupials Sminthopsis-Crassicaudata and Sminthopsis-Macroura

Abstract

Various haematological parameters and morphological aspects were determined for blood collected from 52 fat-tailed dunnarts, Sminthopsis crassicaudata. Compared with those of other marsupials, the erythrocyte and leukocyte counts, haemoglobin concentration and packed cell volume were low, whereas the percentage of reticulocytes (8%) was high. Differential counts revealed a sexual dimorphism for the percentage of neutrophils and lymphocytes present. Blood cell counts, including reticulocyte and differential counts, were also performed on blood from 11 animals of a closely related species, Sminthopsis macroura. For both species mature and developing blood cells from circulating blood, bone marrow, and intestinal mucosa were examined with the light and transmission electron microscope. The unusual features of peripheral blood were: the band forms of neutrophils with annular nuclei; a high percentage of hypersegmented neutrophils; the persistence of polyribosomes in many circulating red blood cells which otherwise appeared mature; the lack of basophils; the absence of eosinophils in S. crassicaudata and the rarity of these leukocytes in S. macroura. The ultrastructure of the developing and circulating blood cells was similar to that previously described for humans, except for the later stages of nuclear maturation in some neutrophils. In these cells annular nuclei developed into rings of beads that then broke to give the typical lobulated nuclei of mature neutrophils. All three types of granulocytes were found in the bone marrow. The leukocytic granules appeared slightly different from their human counterparts.