Assessment of the hemorheological profile of koala and echidna

Abstract

Koala, a marsupial, and echidna, a monotreme, are mammals native to Australia. Blood viscosity (62.5-1250 s −1 ), red blood cell (RBC) deformability, RBC aggregation, aggregability and surface charge, and hematological parameters were measured in blood samples from six koalas and six echidnas and compared to adult human blood. Koala had the largest RBC mean cell volume (107.7 ± 2.6 fl) compared to echidna (81.3 ± 2.6 fl) and humans (88.4 ± 1.2 fl). Echidna blood exhibited the highest viscosity over the entire range of shear rates. Echidna RBC were significantly less deformable than koala RBC but more deformable than human RBC. Echidna RBC had significantly lower aggregability (i.e., aggregation in standardized dextran medium) than koala or human RBC, while aggregation in autologous plasma was similar for the three species. Erythrocyte surface charge as indexed by RBC electrophoretic mobility was similar for human and echidna cells but was 40 % lower for koala RBC. Data obtained during this preliminary study indicate that koala and echidna have distinct hemorheological characteristics; investigation of these properties may reveal patterns relevant to specific behavioral and physiological features of these animals.

Haemorheology of the eastern grey kangaroo and the Tasmanian devil

“…These differences were somewhat unexpected given our recent findings that showed similar whole blood viscosity and RBC aggregation in plasma among a placental mammal (human), a marsupial (koala) and a monotreme (echidna), which represent distant mammalian evolutionary branches (Baskurt et al 2010). The haematology findings for Tasmanian devil blood in the present study were similar to reference values (Isaacks et al 1984).…”

“…Given the general agreement of haemorheology parameters among koala, shortbeaked echidna and human blood (Baskurt et al 2010), the findings of the present study suggest that environmental pressures since the marsupial-monotreme divergence have influenced the development of vastly different strategies to maintain a match between oxygen demand and delivery.…”

“…short-beaked echidna) and a marsupial (i.e. koala) were found to be comparable (Baskurt et al 2010), the remarkably high oxygen-carrying capacity reported for the eastern grey kangaroo and the Tasmanian devil suggests possible rheological adaptations specific to these species (Bartels et al 1966;Isaacks et al 1984). Haematological factors affecting oxygen content are well described for marsupials (Bartels et al 1966;Parsons et al 1970;Isaacks et al 1984;Clark 2004); however, the delivery of oxygen to nutritive exchange vessels also depends on blood flow to those vessels.…”

“…Baskurt and colleagues (Baskurt et al 2010) demonstrated that the rheological properties of blood were generally similar between three taxonomically distant species representing monotreme, marsupial and placental mammals. Conversely, differences in blood rheology (e.g.…”

Lessons from comparative hemorheology studies

“…Weddell seals, bowhead whales) have also been obtained at various shear rates [12,15], but since the measurements did not include shear rates below 37.5 s -1 the data do not reflect the high variation observed in other studies at shear rates below about 1 s -1 [38]. A recent study compared the blood viscosity of koala and echidna with human data, and thus marsupials, monotremes and placental mammals [9], but the lack of low shear data close to 1 s -1 precluded evaluating low-shear variations.…”