Affiliations: Department of Physiology and Biophysics, USC School of Medicine, Los Angeles, CA, 90033, USA | Institute of Marine Science, University of Alaska, Fairbanks, AK, 99775, USA
Abstract: Seals place extreme demands on circulatory blood flow during dives, yet hemorheological information for these marine mammals is limited. We have thus investigated several hematologic and rheologic parameters in three phocid seals: elephant seals (ES, Mirounga angustirostrisl. ringed seals (RS, Phoca hispida) and Weddell seals (WS, Leptonychotes weddelli). Salient results included: 1) elevated hematocrit (ES = 62, RS = 51, WS = 64%); 2) large MCV (ES = 179, RS = 122, WS = 153 fL); 3) increased MCHC (ES = 41, RS = 39, WS = 41 g/dll. with calculated RBC cytoplasmic viscosities based on MCHC being two- to four-fold higher than human; 4) species-specific fibrinogen levels (ES = 0.16, RS = 0.17, WS = 0.66 g/dl). RBC aggregation (Myrenne and ZSR, 40% hematocrit in plasma) was also species specific: 1) extent of aggregation [AI] (ES = 24, RS = 0, WS = 32, human ≈ 17); 2) aggregate strength [GTM] (ES = 105, RS = 3, WS = 220, human ≈ 61s−1); 3) ZSR (ES = 0.62, RS = 0.41, WS = 0.75, human ≈ 0.52). Blood viscosity data (Contraves LS-30, 40% hematocrit in plasma) again indicated variations among species; WS blood was markedly non-Newtonian with elevated low shear viscosity, whereas RS blood exhibited much lower, nearly Newtonian viscosity — ES blood was intermediate in flow behavior. Viewed collectively, these results indicate marked rheologic “abnormalities” for seal blood which, however, are not associated with pathophysiologic findings; they thus suggest adaptive mechanisms in these animals and the potential value of aquatic mammals as model systems for clinical hemorheology studies.
