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Journal of Comparative Physiology B

, Volume 160, Issue 5, pp 593–599 | Cite as

Seasonal changes in the oxygen storage capacity and aerobic dive limits of the muskrat (Ondatra zibethicus)

  • Robert A. MacArthur
Article

Summary

The oxygen storage capacity and partitioning of body oxygen reserves were compared in summer-and winter-acclimatized muskrats (Ondatra zibethicus). Blood volume, blood oxygen capacity, and skeletal muscle myoglobin content were higher in December than in July (P<0.02). Total lung capacity increased only slightly in winter (P>0.05). The oxygen storage capacity of a diving muskrat was calculated at 25.2 ml O2 STPD · kg-1 in July, compared to 35.7 ml O2 STPD · kg-1 in December. Blood comprised the major storage compartment in both seasons, accounting for 57% and 65% of the total oxygen stores in summer and winter, respectively. Based on available oxygen stores and previous estimates of the cost of diving, the aerobic dive limit (ADL) increased from 40.9 s in July to 57.9 s in December. Concurrent behavioral studies suggested that most voluntary diving by muskrats is aerobic. However, the proportion of dives exceeding the calculated ADL of these animals was shown to vary with the context of the dive. Only 3.5% of all dives initiated by muskrats floating in the water exceeded their estimated ADL. Provision of a dry resting site and access to a submerged food source increased this proportion to 18–61%, depending on the underwater distance that foraging muskrats were required to swim. Serial dives exceeding the estimated ADL were not accompanied by extended postdive recovery periods.

Key words

Muskrat, Ondatra zibethicus Diving Oxygen storage capacity Seasonal changes 

Abbreviations

ADL

acrobic dive limit

Hb

hemoglobin

Hct

hematocrit

Mb

myoglobin

PaO2

arterial O2 tension

STPD

standard temperature and pressure, dry

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Copyright information

© Springer-Verlag 1990

Authors and Affiliations

  • Robert A. MacArthur
    • 1
  1. 1.Department of ZoologyUniversity of ManitobaWinnipegCanada

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