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Diving physiology of the Weddell seal

Warren M. Zapol

10.1002/cphy.cp040245

Source: Supplement 14: Handbook of Physiology, Environmental Physiology

Originally published: 1996

Published online: January 2011

Full Article on Wiley Online Library



Abstract

The sections in this article are:

Figure 1. Figure 1.

Weddell seal regional blood flow measured by injecting radioactive microspheres during laboratory diving: percent change of organ blood flow, ml · min · g−1, during simulated diving.
Figure 2. Figure 2.

Schematic diagram of diving computer and mounting system.

courtesy of Drs. G. C. Liggins and R. Elliott
Figure 3. Figure 3.

Layout of ice hut and diving hole on ice sheet

courtesy of Dr. R. D. Hill
Figure 4. Figure 4.

Arterial hemoglobin (Hb) changes during diving and after resurfacing. Dives were divided into short (<17 min) and long (<17 min) dives. Serial sampling during long dives showed that hemoglobin stabilized within 10–12 min. Rate of rise of hemoglobin was close to 1 g · 100 ml−1 · min−1 during the first 10 min. Rate of decrease during recovery was similar.
Figure 5. Figure 5.

Changes in arterial O2 tensions (PaO2) during diving and after resurfacing. Early diving compression hyperoxia is apparent. Lowest PaO2 recorded was 18.2 torr at the end of a 27 min dive. Similar low PaO2 values were recorded at the end of short dives (that is, dives < 17 min). Highest postdive PaO2 values were recorded after dives of long duration. These high values may reflect cooling of the seal.
Figure 6. Figure 6.

One hypothesis explaining the events that lead to a marked increase in circulating hemoglobin concentrations during diving by a 350 kg Weddell seal. Red blood cells (RBC) stored in the spleen at near‐normal O2 and CO2 tensions are released into the portal circulation and subdiaphragmatic capacitance veins and then enter the central circulation via the inferior vena caval sphincter. Effects of RBC release are (1) maintenance or increase of aortic arterial O2 content until reservoir is depleted (usually 10–12 min into long dives), (2) lack of buildup of CO2 until reservoir is emptied (dilution effect), and (3) reduction of initially high N2 tensions (dilution effect). Splenic storage capacity of RBC may amount to 60% of RBC mass, and splenic weight during rest totals at least 7% of body weight; splenic weight is probably greater because splenic venous effluent contains both plasma and RBC (Hct < 100%). PV = plasma volume; RBCV = RBC volume; Hct = hematocrit; BV = blood volume; BW = body weight.
Figure 7. Figure 7.

Heart rate and depth combined with serial determinations of PaN2 during dive. PaN2 values determined early during a dive when pulmonary gas exchange spaces are collapsing. Each sampling time was 30 s.
Figure 8. Figure 8.

Changes in arterial CO2 tension (Paco2) during dive and after resurfacing from short and long dives. Paco2 in long dives did not increase above resting value (42.5 ± 1.63 torr) until 12–13 min into dive but then rose to levels similar to those measured in short dives. Lack of rise in Paco2 early in long dives is believed to be caused by addition of red blood cells with a normal CO2 content. Paco2 in the recovery period rarely decreased below normal levels, despite marked increase of respiratory rate after resurfacing. Decrease of Paco2 after resurfacing was slower if the seal went to sleep.


Figure 1.

Weddell seal regional blood flow measured by injecting radioactive microspheres during laboratory diving: percent change of organ blood flow, ml · min · g−1, during simulated diving.



Figure 2.

Schematic diagram of diving computer and mounting system.

courtesy of Drs. G. C. Liggins and R. Elliott


Figure 3.

Layout of ice hut and diving hole on ice sheet

courtesy of Dr. R. D. Hill


Figure 4.

Arterial hemoglobin (Hb) changes during diving and after resurfacing. Dives were divided into short (<17 min) and long (<17 min) dives. Serial sampling during long dives showed that hemoglobin stabilized within 10–12 min. Rate of rise of hemoglobin was close to 1 g · 100 ml−1 · min−1 during the first 10 min. Rate of decrease during recovery was similar.



Figure 5.

Changes in arterial O2 tensions (PaO2) during diving and after resurfacing. Early diving compression hyperoxia is apparent. Lowest PaO2 recorded was 18.2 torr at the end of a 27 min dive. Similar low PaO2 values were recorded at the end of short dives (that is, dives < 17 min). Highest postdive PaO2 values were recorded after dives of long duration. These high values may reflect cooling of the seal.



Figure 6.

One hypothesis explaining the events that lead to a marked increase in circulating hemoglobin concentrations during diving by a 350 kg Weddell seal. Red blood cells (RBC) stored in the spleen at near‐normal O2 and CO2 tensions are released into the portal circulation and subdiaphragmatic capacitance veins and then enter the central circulation via the inferior vena caval sphincter. Effects of RBC release are (1) maintenance or increase of aortic arterial O2 content until reservoir is depleted (usually 10–12 min into long dives), (2) lack of buildup of CO2 until reservoir is emptied (dilution effect), and (3) reduction of initially high N2 tensions (dilution effect). Splenic storage capacity of RBC may amount to 60% of RBC mass, and splenic weight during rest totals at least 7% of body weight; splenic weight is probably greater because splenic venous effluent contains both plasma and RBC (Hct < 100%). PV = plasma volume; RBCV = RBC volume; Hct = hematocrit; BV = blood volume; BW = body weight.



Figure 7.

Heart rate and depth combined with serial determinations of PaN2 during dive. PaN2 values determined early during a dive when pulmonary gas exchange spaces are collapsing. Each sampling time was 30 s.



Figure 8.

Changes in arterial CO2 tension (Paco2) during dive and after resurfacing from short and long dives. Paco2 in long dives did not increase above resting value (42.5 ± 1.63 torr) until 12–13 min into dive but then rose to levels similar to those measured in short dives. Lack of rise in Paco2 early in long dives is believed to be caused by addition of red blood cells with a normal CO2 content. Paco2 in the recovery period rarely decreased below normal levels, despite marked increase of respiratory rate after resurfacing. Decrease of Paco2 after resurfacing was slower if the seal went to sleep.

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Article Title: Diving physiology of the Weddell seal
 

How to Cite

Warren M. Zapol. Diving physiology of the Weddell seal. Compr Physiol 2011, Supplement 14: Handbook of Physiology, Environmental Physiology: 1049-1056. First published in print 1996. doi: 10.1002/cphy.cp040245