In Vivo Measurements of Lung Volumes in Ringed Seals: Insights from Biomedical Imaging

Abstract

Marine mammals rely on oxygen stored in blood, muscle and lungs to support breath-hold diving and foraging at sea. Here, we used biomedical imaging to examine lung oxygen stores and other key respiratory parameters in living ringed seals (Pusa hispida). Three-dimensional models created from computed tomography (CT) images were used to quantify total lung capacity (TLC), respiratory dead space, minimum air volume and total body volume to improve assessment of lung oxygen storage capacity, scaling relationships and buoyant force estimates. The results suggest that lung oxygen stores determined in vivo are smaller than those derived from postmortem measurements. We also demonstrate that, whereas established allometric relationships hold well for most pinnipeds, these relationships consistently overestimate TLC for the smallest phocid seal. Finally, measures of total body volume reveal differences in body density and net vertical forces in the water column that influence costs associated with diving and foraging in free-ranging seals.

Isochrony in barks of Cape fur seal (Arctocephalus pusillus pusillus) pups and adults

“…While the precise matching of beats in pups could be correlated to less vocal control and therefore more control through muscle tonicity and respiration patterns, those same respiration patterns could be the reason for pups to miss beats. For example, they might be out of breath, as they are considerably smaller, which correlates to smaller lung capacities (Hermann‐Sorensen et al., 2020; Kooyman, 1989; Thometz et al., 2021). For an adult female, it might be easier to maintain a barking bout over a longer time without skipping a beat.…”