Blood volume in hooded seals: implications for diving capacity

Plasma volumes of seven adult hooded seals, Cystophora cristata (two males and five females; body mass (M) range = 110-234 kg), captured on sea ice of f east of Greenland during breeding (March-April), ranged between 35 and 54 mL/kg M (median = 46.5 mL/kg M). Linear regression analysis of haemoglobin (Hb) concentrations (g/dL) and hematocrit (Hct; %) levels in venous blood yielded: Hb = 0.296Hct + 5.53 (r(2) = 0.96, n = 7). Aortic Hct of 11 adult and juvenile seals with contracted and dilated spleens ranged between 62 an d 67% (median = 66.5%, n = 5) and 50 and 67.5% (58.5%, n = 6), respectively , with the differences between groups being significant (p < 0.05). The cal culated blood volume range was 104-162 mL/kg M (median = 139 mL/kg M, n = 7 ). The skeletal muscle mass of two adult females represented 30.8 and 28.1% of their M. Based on this, the body oxygen store of a 150-kg seal was esti mated to be 9.8 L O-2, of which only about 0.9 L O-2 (9%) could be stored i n the fully dilated spleen. In assuming a diving aerobic metabolic rate of 1-2 times the predicted basal metabolic rate, the calculated aerobic dive l imit was estimated to be 11.3-22.6 min.