Therefore we did not include these results in Table 3. We also omitted a questionable estimate of 243 g reported for the brM of harp seal Pagophilus groenlandicus neonates in

Sacher and Staffeldt (1974), because it greatly exceeds mean fresh brM (215 g, n = 41) measured in weaned harp seal pups (Kovacs and Lavigne 1985). Some terrestrial mammals resemble pinnipeds in giving birth to single, precocial young, including several species of ungulate (orders Artiodactyla and Perissodactyla; Oftedal 1985). Terrestrial species with particularly low MF values (~1.5), such as the blue wildebeest (Connochaetes taurinus; Artiodactyla: Bovidae), the llama (Lama glama; Artiodactyla: Camelidae), and the mountain zebra (Equus zebra; Perissodactyla: Equidae) (Mangold-Wirz 1966, Grand 1992) give birth to neonates that Sirolimus mouse are considerably larger (9%–10% of maternal mass) than Weddell seals (Mangold-Wirz 1966, Oftedal 1985, Westlin-van Aarde et al. 1988, Grand 1992, Herrera et al. 2002). Thus the hypothesis that Weddell seals are unusual among precocial mammals in producing large-brained, but small-bodied neonates appears to hold across a broad range of mammals with precocial young. A large brain has physiological consequences for Weddell seal pups as it implies an increased brain

oxygen and substrate demand relative to body mass. Brain tissue does not tolerate any interruption of find more its oxygen or fuel supply, and absolutely requires glucose to function (Sokoloff et al. 1977, Simpson et al. 2007). During starvation and other states characterized by carbohydrate insufficiency, the brain can replace a limited proportion of its glucose requirement by ketone bodies, but this requires high concentrations of ketone bodies (hyperketonemia) in circulation (Robinson and Williamson 1980). There is no evidence that hyperketonemia occurs in nursing phocid seals (Castellini and Costa 1990, Castellini and Rea many 1992), and hence the brain’s metabolic substrate requirements must be met by glucose. If we assume as a first approximation that brain

glucose metabolism of Weddell seal pups and adults is 28 μmol glucose/100 g brain/min, as measured in adult Weddell seals (Murphy et al. 1980), we can calculate daily estimated glucose use by the brain (DGB) of adult (561 g brM, 434 kg BM; Table 3) and neonatal (390 g brM, 28.9 kg BM; Table 3) Weddell seals as: (2) Relative to body mass, the estimated pup brain glucose requirement (0.98 g/kg/d) is more than 10-fold that of the adult (0.094 g/kg/d). However, comparisons on the basis of BM are misleading because metabolic capacity to supply tissue demands, as indicated by whole-body metabolic rate, is also higher on a mass-specific basis in pups. Furthermore, brain (cerebral) metabolic rate, CMR, scales allometrically with brain mass raised to the power of ~0.85 (Mink et al. 1981, Karbowski 2007, Eisert 2011).