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Ponganis, PJ, Kooyman GL, Zornow MH, Castellini MA, Croll DA.  1990.  Cardiac output and stroke volume in swimming harbor seals. Journal of Comparative Physiology B-Biochemical Systemic and Environmental Physiology. 160:473-482.   10.1007/BF00258974   AbstractWebsite

Cardiac output was measured by the thermodilution method in three young harbor seals, at rest and while swimming up to the maximum effort for which they could be trained. Stroke volume was determined by counting heart rate simultaneously with determination of cardiac output. Cardiac outputs varied widely between surface breathing (7.8 and breath-holding while swimming under water (1.8 Stroke volume while at the surface was almost twice the volume while submerged. Surface cardiac output was always near maximal despite work effort, whereas submerged cardiac output gradually increased at higher work efforts. The cardiovascular performance of seals at the maximum MO2 we could induce from them is equivalent to that of the domestic goat.

Ponganis, PJ, Kooyman GL, Zornow MH.  1991.  Cardiac output in swimming California sea lions, Zalophus californianus. Physiological Zoology. 64:1296-1306. AbstractWebsite

Cardiac output was determined by the thermodilution technique in three California sea lions while resting and while swimming. Metabolic rates increased seven-to ninefold above resting rates during maximal exercise. While the sea lions were at rest, stroke volume was also determined by simultaneously counting heart rate during cardiac output determinations. At rest, cardiac output (2.5-3.0 mL kg-1s-1) and stroke volume (2 mL kg-1) were similar to those of harbor seals and terrestrial mammals of similar mass. During exercise, mean cardiac output increased linearly with work load and surface/submerged intervals were short and frequent. The exercise capacity of swimming sea lions appears similar to that of harbor seals, but the exercise response resembles that of terrestrial mammals more than that of harbor seals.

Cristofari, R, Bertorelle G, Ancel A, Benazzo A, Lemaho Y, Ponganis PJ, Stenseth NC, Trathan PN, Whittington JD, Zanetti E, Zitterbart DP, Le Bohec C, Trucchi E.  2016.  Full circumpolar migration ensures evolutionary unity in the Emperor penguin. Nature Communications. 7   10.1038/ncomms11842   AbstractWebsite

Defining reliable demographic models is essential to understand the threats of ongoing environmental change. Yet, in the most remote and threatened areas, models are often based on the survey of a single population, assuming stationarity and independence in population responses. This is the case for the Emperor penguin Aptenodytes forsteri, a flagship Antarctic species that may be at high risk continent-wide before 2100. Here, using genome-wide data from the whole Antarctic continent, we reveal that this top-predator is organized as one single global population with a shared demography since the late Quaternary. We refute the view of the local population as a relevant demographic unit, and highlight that (i) robust extinction risk estimations are only possible by including dispersal rates and (ii) colony-scaled population size is rather indicative of local stochastic events, whereas the species' response to global environmental change is likely to follow a shared evolutionary trajectory.

Zenteno-Savin, T, Leger JS, Ponganis PJ.  2010.  Hypoxemic and ischemic tolerance in emperor penguins. Comparative Biochemistry and Physiology C-Toxicology & Pharmacology. 152:18-23.   10.1016/j.cbpc.2010.02.007   AbstractWebsite

Oxygen store depletion and a diving bradycardia in emperor penguins (Aptenodytes forsteri) expose tissues to critical levels of hypoxemia and ischemia. To assess the prevention of re-perfusion injury and reactive oxygen species (ROS) damage in emperor penguins, superoxide radical production, lipid peroxidation (thiobarbituric acid reactive substances (TBARS)), and antioxidant enzyme activity profiles in biopsy samples from muscle and liver were determined and compared to those in the chicken and 8 species of flighted marine birds (non-divers and plunge divers). In muscle of emperor penguins, superoxide production and TBARS levels were not distinctly different from those in the other species; among the antioxidant enzymes, catalase (CAT) and glutathione-S-transferase (GST) activities were significantly elevated above all species. In the liver of emperor penguins, TBARS levels were not significantly different from other species; only CAT activity was significantly elevated, although GST and glutathione peroxidase (GPX) activities were 2-3 times higher than those in other species. The potential for ROS formation and lipid peroxidation is not reduced in the pectoral muscle or liver of the emperor penguin. Scavenging of hydrogen peroxide by CAT and the conjugation of glutathione with reactive intermediates and peroxides by GST and GPX appear to be important in the prevention of ROS damage and re-perfusion injury in these birds. (C) 2010 Elsevier Inc. All rights reserved.