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First published online October 7, 2004
Journal of Experimental Biology 207, 3891-3898 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01222

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Developmental changes in cardiorespiratory patterns associated with terrestrial apnoeas in harbour seal pups

Jennifer L. Lapierre^1,*, Jason F. Schreer^2,, Jennifer M. Burns³ and Michael O. Hammill⁴

¹ Department of Biology, University of Waterloo, Waterloo, ON, Canada N2L 3K8
² Department of Biology, SUNY Potsdam, Potsdam, NY 13676, USA
³ Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
⁴ Maurice Lamontagne Institute, Department of Fisheries and Oceans, Mont-Joli, QC, Canada G5H 3Z4

Author for correspondence (e-mail: schreejf{at}potsdam.edu)

Accepted 29 July 2004

During the nursing period seals undergo several physiological and behavioural changes. A key component of development is increased cardiorespiratory control, fundamental for breath-holding and thus diving. This study focused on the ontogenetic changes in cardiac responses to respiration in quietly resting, pre-weaned harbour seal pups (Phoca vitulina). During periods of quiet rest, breathing became episodic, eupnoea interspersed with periods of apnoea. Little change was observed in respiration (35 breaths min^–1) and eupnoeic heart rate (160 beats min^–1) throughout the nursing period. However, apnoea duration increased (from 20 to 40 s), while apnoeic heart rate decreased with age (from 150 to 90 beats min^–1). The observed decline in apnoeic heart rate resulted from an increase in cardiorespiratory control as pups approached weaning, evident by the ability to maintain a lower heart rate more consistently. Similar changes in cardiorespiratory patterns have been reported for elephant and Weddell seals. Due to the early onset of independent foraging, however, the rate of cardiorespiratory control development was more rapid in harbour seals. Our findings suggest that by 1 month of age, harbour seal pups possess the cardiorespiratory control necessary to sustain long-duration apnoeas, fundamental for proficient diving and successful foraging upon weaning.

Key words: apnoea, eupnoea, respiration, heart rate, bradycardia, sleep, ontogeny, cardiorespiratory control, harbour seal, Phoca vitulina

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