American Journal of Physiology-regulatory Integrative and Comparative Physiology, Aug 1, 1986
Food intake (FI), feeding activity (FA), and body mass (BM) were recorded continuously throughout... more Food intake (FI), feeding activity (FA), and body mass (BM) were recorded continuously throughout a 13-mo period in Svalbard rock ptarmigan kept under natural conditions of light and ambient temperature at Svalbard (79 degrees N). FI was persistently high from March until August, including the period when daylight is continuous, whereas it was low from November until January, when it is permanently dark. From August until November, BM doubled, while FI dropped to one-third. BM fell rapidly from mid-November until April despite a doubling of FI from February until March. From August until mid-November and from February until mid-April FA occurred mainly during the light period of the day. From late November until February and from mid-April until August intermittent FA occurred continuously. It is suggested that the seasonal changes in BM are not determined by FI alone but depend heavily on seasonal changes in locomotor activity as reflected in FA.
Ross seals (Ommatophoca rossii) are the least studied and scarcest of the Antarctic pinnipeds. On... more Ross seals (Ommatophoca rossii) are the least studied and scarcest of the Antarctic pinnipeds. Only two studies exist on its at-sea movements: four and eight individuals tracked in the Amundsen and Weddell seas respectively. Diving behaviour has only been recorded for seven individuals and no longitudinal stable isotope data exist. Between 2016 and 2019, we deployed 15 satellite trackers of which seven measured diving behaviour and collected whiskers for bulk-stable isotope analyses from 25 individuals, making this the single largest study on Ross seals to date. Tracking data was combined with the eight animals previously tracked in the Weddell Sea to build the first habitat model for the species. Ross seals travelled away from the Antarctic pack-ice to forage pelagically on myctophid fish and cephalopods. This is reflected in the sequentially sampled bulk stable-isotope data from collected whiskers, with oscillations in δ13C and δ15N values reflecting their south-north movements. During winter, they spend most of their time tracking the marginal sea ice while summer is spent in open water. Ross seals dive deeper, but not longer, during the day presumably following the diel vertical migrations of their preferred prey and haul-out behaviour is influenced by lunar phases. The habitat model shows that sea-surface temperature is the most important indicator of foraging behaviour and they prefer to forage in a very narrow temperature band. This contrasts with suggestions that Ross seals might benefit from climate change due to the receding ice and reduced travel distances required to reach the open water.
Food intake (PI), body mass (BM), and compartmental growth were recorded for 12 mo in four captiv... more Food intake (PI), body mass (BM), and compartmental growth were recorded for 12 mo in four captive 2–4‐yr‐old male harp seals (Phoca groenlandica), exposed to an artificial light regime that closely resembled natural day length at 69°. In early May before molting, both FZ and BM decreased in all four animals. Total body fat (TBF) declined from 51% of BM in March (n = 4) to 30% in August (n = 2), while total body water (TBW) concomitantly increased from 37% to 51% and total body protein (TBP) from 11% to 17%. In July FI started to increase, while BM started to increase in August. TBF increased while TBW and TBP decreased from August, all three parameters reaching a stable level in October at 47%, 39%, and 12%, respectively. Thereafter, body composition was maintained rather constant until May. Between October and March/April FI fluctuated for all animals, while BM showed a fairly steady increase. Average daily amount of capelin consumed was 2.67 kg·d−1, equivalent to 25,600 kJ·d−1, o...
Daily variations of pineal and plasma melatonin and plasma thyroid hormones were measured in harp... more Daily variations of pineal and plasma melatonin and plasma thyroid hormones were measured in harp seals (Phoca groenlandica), grey seals (Halichoerus grypus), and hooded seals (Cystophora cristata), ranging in age from newborn to 14 days. In newborn harp seals the mean mass of the pineal gland was 273 mg (+/- 45 SEM, n = 11), containing 49 ng (median) melatonin. In newborn, 4- and 10-day-old grey seals, the pineal mass was similar, weighing on average 337 mg (+/- 74, n = 6) and containing 90 ng melatonin. Two newborn hooded seal pups had pineals weighing 520 and 1289 mg, with 254 and 7600 ng melatonin, respectively. There were no day-night differences in the pineal contents of melatonin or in the number of pineal beta-adrenergic receptors measured in newborn harp seals, and, in newborn, 4- and 10-day-old grey seals, there were no day-night or age differences in pineal melatonin content. Plasma melatonin levels were 10 times higher in newborn seals than in two 10-day-old grey seals and one 14-day-old harp seal pup. In all seal pups, the levels exhibited a 24-hr rhythmicity, with increasing night- and decreasing daytime concentrations. Plasma levels of thyroxine (T4) and triiodothyronine (T3) were generally higher in newborn seals than in 10- and 14-day-old seals or in adult females. There was no apparent 24-hr rhythmicity, but the thyroid hormone levels generally declined throughout each sampling sequence. High pineal and thyroid activities may play a thermoregulatory role in newborn seals, but the results do not indicate a stimulatory action of melatonin in the peripheral conversion of T4 to T3. It is speculated that the large and active pineal gland, particularly in newborn seals, may be related to aspects of their diving habit.
ABSTRACT Resting metabolic rate was measured at different ambient temperatures in Svalbard Ptarmi... more ABSTRACT Resting metabolic rate was measured at different ambient temperatures in Svalbard Ptarmigan, Norwegian Rock Ptarmigan and Norwegian Willow Ptarmigan at different times of the year. All three species/subspecies exhibited a significant decrease in mass-specific resting metabolism from summer to winter. At both seasons resting metabolism was higher than predicted by Aschoff and Pohl (1970), but lower than the predictions of Weathers (1979) for all three species/subspecies. The mass-specific conductance (MSC) was significantly (P < 0.05) lower, i.e. insulation was better, in winter than during summer in Svalbard Ptarmigan and Willow Ptarmigan, while Rock Parmigan did not show seasonal changes in MSC. MSC of all three species/subspecies was lower than predicted both by Herreid and Kessel (1967) and by Aschoff (1981), both in summer and in winter. MSC of Svalbard Ptarmigan was significantly lower than MSC of Rock Ptarmigan and Willow Ptarmigan, both in summer and in winter. During spring (March-May) when the Svalbard Ptarmigan is still in winter plumage, but devoid of subcutaneous fat, the MSC was the same as during summer. This indicates that the subcutaneous deposits of fat contribute significantly to the thermal insulation of these high-arctic birds during winter.
On submersion, the cardiovascular system of naturally diving animals is virtually transformed int... more On submersion, the cardiovascular system of naturally diving animals is virtually transformed into a heart-brain-lung preparation as the result of intense and highly selective neurogenic vasoconstriction. A supply of oxygen from the circulating blood cells to the heart and the brain is thereby secured. Peripheral tissues, e.g. muscles and kidneys, have to depend on local stores of oxygen, i.e. myoglobin, or, when these are exhausted, on anaerobic metabolism. In spite of such physiological adjustments, however, arterial pO2 will inevitably decrease throughout the underwater episode. In prolonged dives values lower than 10mmHg can be observed. Moreover, the ischaemia in the peripheral tissues will, in some animals, e.g. arctic seals and whales, result in a profound decrease in the temperature of tissues such as the skin. The aim of the present report is to review some of the more important biochemical mechanisms that allow diving mammals and birds to cope with the above-mentioned combined asphyxic and temperature stresses for prolonged periods. Some of the osmotic problems arising from the rapid wash-out of acidic metabolic end products from the previously ischaemic tissues on emergence are also discussed.
American Journal of Physiology-regulatory Integrative and Comparative Physiology, Aug 1, 1989
Expired air temperature (Tex), metabolic rate (MR), and skin (Ts) and body (Tb; rectal) temperatu... more Expired air temperature (Tex), metabolic rate (MR), and skin (Ts) and body (Tb; rectal) temperatures were recorded in four or five young (1-2 yr) harp seals (Phoca groenlandica) in air [mean air temperature (Ta) = -30, -10, or 10 degrees C] and in water [mean water temperature (Tw) = 2.3 or 24.8 degrees C, with Ta = -30, -10, 0, or 10 degrees C]. Apparent lower critical temperature was below -10 degrees C in air. Above this Ta, mean MR was 5.85 W.kg-0.75 (2.23 W.kg-1), while mean MR was 12.56 W.kg-0.75 (4.69 W.kg-1) at Ta -30 degrees C. When seals were immersed in water of 2.3 degrees C, mean MR was 6.13 W.kg-0.75 (2.31 W.kg-1), regardless of Ta. At Ta -30, -10, and 10 degrees C, mean Tex in air were 9.5, 13.0, and 25.0 degrees C, respectively. The corresponding values for seals in water (Tw = 2.3 degrees C) were 8.0, 9.5, and 15.5 degrees C, respectively. The low Tex recorded at Ta -30 and -10 degrees C in air and at all Ta in water (Tw = 2.3 degrees C) suggests that heat was conserved by nasal heat exchange. At Ta 10 degrees C, mean Tex of seals in air was approximately 10 degrees C higher than mean Tex of seals in water (Tw = 2.3 degrees C). Furthermore, seals subjected to a Tw of 24.8 degrees C at Ta 0 degrees C had a mean Tex 10 degrees C higher than when subjected to Tw 2.3 degrees C at the same Ta. These observations suggest that Tex in seals is under thermoregulatory control. In a series of forced dives of up to 5-min duration Tex was found to be the same before and after the dive regardless of dive duration and Ta.
As upper trophic level predators with a circumpolar distribution, the antarctic pack ice seals (c... more As upper trophic level predators with a circumpolar distribution, the antarctic pack ice seals (crabeater, Lobodon carcinophagus; leopard, Hydrurga leptonyx; Ross, Ommatophoca rossii; and Weddell, Leptonychotes weddelli) provide a potential source of information about ecosystem interactions and environmental variability integrated over a wide range of spatial and temporal scales. In recent years, increasing attention has been focused on the need to conduct antarctic pack-ice seal research, and a multifaceted international research initiative to address priority pack-ice seal research topics is being developed: the Antarctic Pack Ice Seals (APIS) Program.
... foraging. An infrared theft alarm (JostyKit? JK 15 and JK 16) was installed in each funnel an... more ... foraging. An infrared theft alarm (JostyKit? JK 15 and JK 16) was installed in each funnel and connected to an event recorder (Angus? Easterline, serie S) to monitor the chicks' traffic out and in of the heated compartment (Fig. ...
It has been demonstrated that cardiac receptors, most likely of the left ventricular type, are pr... more It has been demonstrated that cardiac receptors, most likely of the left ventricular type, are present also in the duck's heart. These receptors and their reflex responses (i.e. bradycardia and hypotension) could be blocked by intrapericardial administration of lidocaine. Initially, such receptor blockade did not affect efferent vagal control of heart rate, as revealed by undiminished bradycardia in response to a standardized vagal stimulation. After cardiac receptor blockade, however, the duck's normal bradycardia response to head immersion was greatly reduced. The cardiovascular response to submersion was now instead characterized by a marked rise in arterial pressure, with superimposed bouts of intensified bradycardia and pressure reduction, evidently induced reflexly from the arterial baroreceptors. Meanwhile, the bradycardia response to standardized efferent vagal stimulation was still the same as before intrapericardial lidocaine injection. These results suggest that the marked rise in cardiac filling pressure following the intense chemo‐receptor‐induced constriction of both resistance and capacitance vessels, activates ventricular stretch receptors signalling in vagal afferents. Apparently, the activation of these receptors contributes crucially to the bradycardia and reduction of cardiac output, which balance off the greatly increased peripheral resistance in the diving duck.
American Journal of Physiology-regulatory Integrative and Comparative Physiology, Aug 1, 1986
Food intake (FI), feeding activity (FA), and body mass (BM) were recorded continuously throughout... more Food intake (FI), feeding activity (FA), and body mass (BM) were recorded continuously throughout a 13-mo period in Svalbard rock ptarmigan kept under natural conditions of light and ambient temperature at Svalbard (79 degrees N). FI was persistently high from March until August, including the period when daylight is continuous, whereas it was low from November until January, when it is permanently dark. From August until November, BM doubled, while FI dropped to one-third. BM fell rapidly from mid-November until April despite a doubling of FI from February until March. From August until mid-November and from February until mid-April FA occurred mainly during the light period of the day. From late November until February and from mid-April until August intermittent FA occurred continuously. It is suggested that the seasonal changes in BM are not determined by FI alone but depend heavily on seasonal changes in locomotor activity as reflected in FA.
Ross seals (Ommatophoca rossii) are the least studied and scarcest of the Antarctic pinnipeds. On... more Ross seals (Ommatophoca rossii) are the least studied and scarcest of the Antarctic pinnipeds. Only two studies exist on its at-sea movements: four and eight individuals tracked in the Amundsen and Weddell seas respectively. Diving behaviour has only been recorded for seven individuals and no longitudinal stable isotope data exist. Between 2016 and 2019, we deployed 15 satellite trackers of which seven measured diving behaviour and collected whiskers for bulk-stable isotope analyses from 25 individuals, making this the single largest study on Ross seals to date. Tracking data was combined with the eight animals previously tracked in the Weddell Sea to build the first habitat model for the species. Ross seals travelled away from the Antarctic pack-ice to forage pelagically on myctophid fish and cephalopods. This is reflected in the sequentially sampled bulk stable-isotope data from collected whiskers, with oscillations in δ13C and δ15N values reflecting their south-north movements. During winter, they spend most of their time tracking the marginal sea ice while summer is spent in open water. Ross seals dive deeper, but not longer, during the day presumably following the diel vertical migrations of their preferred prey and haul-out behaviour is influenced by lunar phases. The habitat model shows that sea-surface temperature is the most important indicator of foraging behaviour and they prefer to forage in a very narrow temperature band. This contrasts with suggestions that Ross seals might benefit from climate change due to the receding ice and reduced travel distances required to reach the open water.
Food intake (PI), body mass (BM), and compartmental growth were recorded for 12 mo in four captiv... more Food intake (PI), body mass (BM), and compartmental growth were recorded for 12 mo in four captive 2–4‐yr‐old male harp seals (Phoca groenlandica), exposed to an artificial light regime that closely resembled natural day length at 69°. In early May before molting, both FZ and BM decreased in all four animals. Total body fat (TBF) declined from 51% of BM in March (n = 4) to 30% in August (n = 2), while total body water (TBW) concomitantly increased from 37% to 51% and total body protein (TBP) from 11% to 17%. In July FI started to increase, while BM started to increase in August. TBF increased while TBW and TBP decreased from August, all three parameters reaching a stable level in October at 47%, 39%, and 12%, respectively. Thereafter, body composition was maintained rather constant until May. Between October and March/April FI fluctuated for all animals, while BM showed a fairly steady increase. Average daily amount of capelin consumed was 2.67 kg·d−1, equivalent to 25,600 kJ·d−1, o...
Daily variations of pineal and plasma melatonin and plasma thyroid hormones were measured in harp... more Daily variations of pineal and plasma melatonin and plasma thyroid hormones were measured in harp seals (Phoca groenlandica), grey seals (Halichoerus grypus), and hooded seals (Cystophora cristata), ranging in age from newborn to 14 days. In newborn harp seals the mean mass of the pineal gland was 273 mg (+/- 45 SEM, n = 11), containing 49 ng (median) melatonin. In newborn, 4- and 10-day-old grey seals, the pineal mass was similar, weighing on average 337 mg (+/- 74, n = 6) and containing 90 ng melatonin. Two newborn hooded seal pups had pineals weighing 520 and 1289 mg, with 254 and 7600 ng melatonin, respectively. There were no day-night differences in the pineal contents of melatonin or in the number of pineal beta-adrenergic receptors measured in newborn harp seals, and, in newborn, 4- and 10-day-old grey seals, there were no day-night or age differences in pineal melatonin content. Plasma melatonin levels were 10 times higher in newborn seals than in two 10-day-old grey seals and one 14-day-old harp seal pup. In all seal pups, the levels exhibited a 24-hr rhythmicity, with increasing night- and decreasing daytime concentrations. Plasma levels of thyroxine (T4) and triiodothyronine (T3) were generally higher in newborn seals than in 10- and 14-day-old seals or in adult females. There was no apparent 24-hr rhythmicity, but the thyroid hormone levels generally declined throughout each sampling sequence. High pineal and thyroid activities may play a thermoregulatory role in newborn seals, but the results do not indicate a stimulatory action of melatonin in the peripheral conversion of T4 to T3. It is speculated that the large and active pineal gland, particularly in newborn seals, may be related to aspects of their diving habit.
ABSTRACT Resting metabolic rate was measured at different ambient temperatures in Svalbard Ptarmi... more ABSTRACT Resting metabolic rate was measured at different ambient temperatures in Svalbard Ptarmigan, Norwegian Rock Ptarmigan and Norwegian Willow Ptarmigan at different times of the year. All three species/subspecies exhibited a significant decrease in mass-specific resting metabolism from summer to winter. At both seasons resting metabolism was higher than predicted by Aschoff and Pohl (1970), but lower than the predictions of Weathers (1979) for all three species/subspecies. The mass-specific conductance (MSC) was significantly (P < 0.05) lower, i.e. insulation was better, in winter than during summer in Svalbard Ptarmigan and Willow Ptarmigan, while Rock Parmigan did not show seasonal changes in MSC. MSC of all three species/subspecies was lower than predicted both by Herreid and Kessel (1967) and by Aschoff (1981), both in summer and in winter. MSC of Svalbard Ptarmigan was significantly lower than MSC of Rock Ptarmigan and Willow Ptarmigan, both in summer and in winter. During spring (March-May) when the Svalbard Ptarmigan is still in winter plumage, but devoid of subcutaneous fat, the MSC was the same as during summer. This indicates that the subcutaneous deposits of fat contribute significantly to the thermal insulation of these high-arctic birds during winter.
On submersion, the cardiovascular system of naturally diving animals is virtually transformed int... more On submersion, the cardiovascular system of naturally diving animals is virtually transformed into a heart-brain-lung preparation as the result of intense and highly selective neurogenic vasoconstriction. A supply of oxygen from the circulating blood cells to the heart and the brain is thereby secured. Peripheral tissues, e.g. muscles and kidneys, have to depend on local stores of oxygen, i.e. myoglobin, or, when these are exhausted, on anaerobic metabolism. In spite of such physiological adjustments, however, arterial pO2 will inevitably decrease throughout the underwater episode. In prolonged dives values lower than 10mmHg can be observed. Moreover, the ischaemia in the peripheral tissues will, in some animals, e.g. arctic seals and whales, result in a profound decrease in the temperature of tissues such as the skin. The aim of the present report is to review some of the more important biochemical mechanisms that allow diving mammals and birds to cope with the above-mentioned combined asphyxic and temperature stresses for prolonged periods. Some of the osmotic problems arising from the rapid wash-out of acidic metabolic end products from the previously ischaemic tissues on emergence are also discussed.
American Journal of Physiology-regulatory Integrative and Comparative Physiology, Aug 1, 1989
Expired air temperature (Tex), metabolic rate (MR), and skin (Ts) and body (Tb; rectal) temperatu... more Expired air temperature (Tex), metabolic rate (MR), and skin (Ts) and body (Tb; rectal) temperatures were recorded in four or five young (1-2 yr) harp seals (Phoca groenlandica) in air [mean air temperature (Ta) = -30, -10, or 10 degrees C] and in water [mean water temperature (Tw) = 2.3 or 24.8 degrees C, with Ta = -30, -10, 0, or 10 degrees C]. Apparent lower critical temperature was below -10 degrees C in air. Above this Ta, mean MR was 5.85 W.kg-0.75 (2.23 W.kg-1), while mean MR was 12.56 W.kg-0.75 (4.69 W.kg-1) at Ta -30 degrees C. When seals were immersed in water of 2.3 degrees C, mean MR was 6.13 W.kg-0.75 (2.31 W.kg-1), regardless of Ta. At Ta -30, -10, and 10 degrees C, mean Tex in air were 9.5, 13.0, and 25.0 degrees C, respectively. The corresponding values for seals in water (Tw = 2.3 degrees C) were 8.0, 9.5, and 15.5 degrees C, respectively. The low Tex recorded at Ta -30 and -10 degrees C in air and at all Ta in water (Tw = 2.3 degrees C) suggests that heat was conserved by nasal heat exchange. At Ta 10 degrees C, mean Tex of seals in air was approximately 10 degrees C higher than mean Tex of seals in water (Tw = 2.3 degrees C). Furthermore, seals subjected to a Tw of 24.8 degrees C at Ta 0 degrees C had a mean Tex 10 degrees C higher than when subjected to Tw 2.3 degrees C at the same Ta. These observations suggest that Tex in seals is under thermoregulatory control. In a series of forced dives of up to 5-min duration Tex was found to be the same before and after the dive regardless of dive duration and Ta.
As upper trophic level predators with a circumpolar distribution, the antarctic pack ice seals (c... more As upper trophic level predators with a circumpolar distribution, the antarctic pack ice seals (crabeater, Lobodon carcinophagus; leopard, Hydrurga leptonyx; Ross, Ommatophoca rossii; and Weddell, Leptonychotes weddelli) provide a potential source of information about ecosystem interactions and environmental variability integrated over a wide range of spatial and temporal scales. In recent years, increasing attention has been focused on the need to conduct antarctic pack-ice seal research, and a multifaceted international research initiative to address priority pack-ice seal research topics is being developed: the Antarctic Pack Ice Seals (APIS) Program.
... foraging. An infrared theft alarm (JostyKit? JK 15 and JK 16) was installed in each funnel an... more ... foraging. An infrared theft alarm (JostyKit? JK 15 and JK 16) was installed in each funnel and connected to an event recorder (Angus? Easterline, serie S) to monitor the chicks' traffic out and in of the heated compartment (Fig. ...
It has been demonstrated that cardiac receptors, most likely of the left ventricular type, are pr... more It has been demonstrated that cardiac receptors, most likely of the left ventricular type, are present also in the duck's heart. These receptors and their reflex responses (i.e. bradycardia and hypotension) could be blocked by intrapericardial administration of lidocaine. Initially, such receptor blockade did not affect efferent vagal control of heart rate, as revealed by undiminished bradycardia in response to a standardized vagal stimulation. After cardiac receptor blockade, however, the duck's normal bradycardia response to head immersion was greatly reduced. The cardiovascular response to submersion was now instead characterized by a marked rise in arterial pressure, with superimposed bouts of intensified bradycardia and pressure reduction, evidently induced reflexly from the arterial baroreceptors. Meanwhile, the bradycardia response to standardized efferent vagal stimulation was still the same as before intrapericardial lidocaine injection. These results suggest that the marked rise in cardiac filling pressure following the intense chemo‐receptor‐induced constriction of both resistance and capacitance vessels, activates ventricular stretch receptors signalling in vagal afferents. Apparently, the activation of these receptors contributes crucially to the bradycardia and reduction of cardiac output, which balance off the greatly increased peripheral resistance in the diving duck.
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