Hemoglobin concentrations and blood gas tensions of free-diving Weddell seals

Abstract

Arterial blood gas tensions, pH, and hemoglobin concentrations were measured in four free-diving Weddell seals Leptonychotes weddelli. A microprocessor-controlled sampling system enabled us to obtain 24 single and 31 serial aortic blood samples. The arterial O2 tension (PaO2) at rest [78 +/- 13 (SD) Torr] increased with diving compression to a maximum measured value of 232 Torr and then rapidly decreased to 25-35 Torr. The lowest diving PaO2 we measured was 18 Torr just before the seal surfaced from a 27-min dive. A consistent increase of arterial hemoglobin concentrations from 15.1 +/- 1.10 to 22.4 +/- 1.41 g/100 ml (dives less than 17 min) and to 25.4 +/- 0.79 g/100 ml (dives greater than 17 min) occurred during each dive. We suggest that an extension of the sympathetic outflow of the diving reflex possibly caused profound contraction of the Weddell seal's very large spleen (0.89% of body wt at autopsy), although we have no direct evidence. This contraction may have injected large quantities of red blood cells (2/3 of the total) into the seal's central circulation during diving and allowed arterial O2 content to remain constant for the first 15-18 min of long dives. The increase of arterial CO2 tensions during the dive and the compression increase of arterial N2 tensions were also moderated by injecting red blood cells sequestered at ambient pressure. After each dive circulating red blood cells are oxygenated and rapidly sequestered, possibly in the spleen during the first 15 min of recovery.

Effects of forced diving on the spleen and hepatic sinus in northern elephant seal pups

“…Although the spleen has long been suspected as the source of the RBCs released during diving, the rate of splenic contraction has presented an apparent contradiction to the gradual divinginduced rise in Hct (2,6). In this study, maximal Hct occurred after the 7-min dive had concluded, whereas the spleen had released the majority of its RBCs by dive min 2.…”

“…hocid seals exhibit a higher hematocrit (Hct) during apnea and diving than during periods of eupneic respiration (1)(2)(3)(4). This variation in red cell mass indicates that seals have some method of sequestering red cells during nonapneic events.…”

“…Bryden and Lim (5) found the Hct values of elephant seal pups to be highly variable and suggested that the spleen acts as a dynamic reservoir for erythrocytes, releasing RBCs into general circulation when required. Qvist et al (2) recorded a distinct rise in Weddell seal Hct during diving and suggested that the total red cell mass is partitioned between general circulation and the splenic reservoir. The concept of splenic red cell storage is well accepted by many researchers, and a diving-induced sympathetic vasoconstriction is thought to be the stimulus for splenic contraction and subsequent injection of oxygenated RBCs into circulation (2,4,6,7).…”

“…Complete splenic contraction occurs within 3 min of catecholamine stimulation, yet peak Hct is not observed until 15-25 min after the spleen has contracted (2,6). The delay between splenic contraction and changes in peripheral venous Hct may represent an equilibration between the splenic reservoir and the venous circulatory blood pools (6), but no evidence exists to substantiate this belief.…”

Genetic diversity of coastal bottlenose dolphins revealed by structurally and functionally diverse hemoglobins

“…Many studies have reported that these organisms have higher than typical vertebrate levels of blood volume, Hb concentrations, hematocrit, and myoglobin concentrations (Ridgway and Johnston, 1966;Bryden and Lim, 1969;Elsner, 1969;Kooyman et al, 1980;Vogl and Fisher, 1982;Cornell, 1983;Duffield, Ridgway and Cornell, 1983;Snyder, 1983;Kanwisher and Ridgway, 1983;Ridgway et al, 1984;Qvist et al, 1986;Hedrick, Duffield and Cornell, 1986;Kooyman, 1986).…”