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O2 store management in diving emperor penguins

By P. J. Ponganis, T. K. Stockard, J. U. Meir, C. L. Williams, K. V. Ponganis and R. Howard

Abstract

In order to further define O2 store utilization during dives and understand the physiological basis of the aerobic dive limit (ADL, dive duration associated with the onset of post-dive blood lactate accumulation), emperor penguins (Aptenodytes forsteri) were equipped with either a blood partial pressure of oxygen (PO2) recorder or a blood sampler while they were diving at an isolated dive hole in the sea ice of McMurdo Sound, Antarctica. Arterial PO2 profiles (57 dives) revealed that (a) pre-dive PO2 was greater than that at rest, (b) PO2 transiently increased during descent and (c) post-dive PO2 reached that at rest in 1.92±1.89 min (N=53). Venous PO2 profiles (130 dives) revealed that (a) pre-dive venous PO2 was greater than that at rest prior to 61% of dives, (b) in 90% of dives venous PO2 transiently increased with a mean maximum PO2 of 53±18 mmHg and a mean increase in PO2 of 11±12 mmHg, (c) in 78% of dives, this peak venous PO2 occurred within the first 3 min, and (d) post-dive venous PO2 reached that at rest within 2.23±2.64 min (N=84). Arterial and venous PO2 values in blood samples collected 1–3 min into dives were greater than or near to the respective values at rest. Blood lactate concentration was less than 2 mmol l–1 as far as 10.5 min into dives, well beyond the known ADL of 5.6 min. Mean arterial and venous PN2 of samples collected at 20–37 m depth were 2.5 times those at the surface, both being 2.1±0.7 atmospheres absolute (ATA; N=3 each), and were not significantly different. These findings are consistent with the maintenance of gas exchange during dives (elevated arterial and venous PO2 and PN2 during dives), muscle ischemia during dives (elevated venous PO2, lack of lactate washout into blood during dives), and arterio-venous shunting of blood both during the surface period (venous PO2 greater than that at rest) and during dives (arterialized venous PO2 values during descent, equivalent arterial and venous PN2 values during dives). These three physiological processes contribute to the transfer of the large respiratory O2 store to the blood during the dive, isolation of muscle metabolism from the circulation during the dive, a decreased rate of blood O2 depletion during dives, and optimized loading of O2 stores both before and after dives. The lack of blood O2 depletion and blood lactate elevation during dives beyond the ADL suggests that active locomotory muscle is the site of tissue lactate accumulation that results in post-dive blood lactate elevation in dives beyond the ADL

Topics: Research Article
Publisher: Company of Biologists
OAI identifier: oai:pubmedcentral.nih.gov:2720999
Provided by: PubMed Central
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