Aerobic capacities in the skeletal muscles of Weddell seals: key to longer dive durations?

SUMMARYIn contrast to terrestrial animals that function under hypoxic conditions but display the typical exercise response of increasing ventilation and cardiac output, marine mammals exercise under a different form of hypoxic stress. They function for the duration of a dive under progressive asphyxia,which is the combination of increasing hypoxia, hypercapnia and acidosis. Our previous studies on short-duration, shallow divers found marked adaptations in their skeletal muscles, which culminated in enhanced aerobic capacities that are similar to those of atheltic terrestrial mammals. The purpose of the present study was to assess the aerobic capacity of skeletal muscles from long-duration divers. Swimming and non-swimming muscles were collected from adult Weddell seals, Leptonychotes weddelli, and processed for morphometric analysis, enzymology, myoglobin concentrations and fiber-type distribution. The results showed that the skeletal muscles of Weddell seals do not have enhanced aerobic capacities compared with those of terrestrial mammals but are adapted to maintain low levels of an aerobic lipid-based metabolism, especially under the hypoxic conditions associated with diving. The lower aerobic capacity of Weddell seal muscle as compared with that of shorter-duration divers appears to reflect their energy-conserving modes of locomotion, which enable longer and deeper dives.

Download Full-text

Marine mammals and Emperor penguins: a few applications of the Krogh principle

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00264.2014 ◽

2015 ◽

Vol 308 (2) ◽

pp. R96-R104 ◽

Cited By ~ 4

Author(s):

Gerald Kooyman

Keyword(s):

Marine Mammals ◽

Blood Gases ◽

Weddell Seal ◽

Dive Duration ◽

Positive Contribution ◽

Lung Collapse ◽

Flow Rates ◽

Weddell Seals ◽

Arterial Blood ◽

Emperor Penguins

The diving physiology of aquatic animals at sea began 50 years ago with studies of the Weddell seal. Even today with the advancements in marine recording and tracking technology, only a few species are suitable for investigation. The first experiments were in McMurdo Sound, Antarctica. In this paper are examples of what was learned in Antarctica and elsewhere. Some methods employed relied on willingness of Weddell seals and emperor penguins to dive under sea ice. Diving depth and duration were obtained with a time depth recorder. Some dives were longer than an hour and as deep as 600 m. From arterial blood samples, lactate and nitrogen concentrations were obtained. These results showed how Weddell seals manage their oxygen stores, that they become reliant on a positive contribution of anaerobic metabolism during a dive duration of more than 20 min, and that nitrogen blood gases remain so low that lung collapse must occur at about 25 to 50 m. This nitrogen level was similar to that determined in elephant seals during forcible submersion with compression to depths greater than 100 m. These results led to further questions about diving mammal's terminal airway structure in the lungs. Much of the strengthening of the airways is not for avoiding the “bends,” by enhancing lung collapse at depth, but for reducing the resistance to high flow rates during expiration. The most exceptional examples are the small whales that maintain high expiratory flow rates throughout the entire vital capacity, which represents about 90% of their total lung capacity.

Download Full-text

Growth of the Weddell Seal, Leptonychotes weddelli (Pinnipedia)

Australian Journal of Zoology ◽

10.1071/zo9840033 ◽

1984 ◽

Vol 32 (1) ◽

pp. 33 ◽

Cited By ~ 16

Author(s):

MM Bryden ◽

MSR Smith ◽

RA Tedman ◽

DW Featherston

Keyword(s):

Body Weight ◽

Birth Weight ◽

Body Length ◽

Marine Mammals ◽

Weddell Seal ◽

Multiple Regression Equation ◽

Consistent Difference ◽

Similar Data ◽

Suckling Period ◽

Weddell Seals

Birth weight was more than trebled during the 6-week suckling period in Weddell seals, and increments in girth measurements were greater than increments in standard length. There was a very highly significant relationship between body weight and length and girth, but no consistent difference between the sexes in birth weight or growth during the suckling period. The distribution of body length frequencies, and regression of body length on age of juvenile and adult seals, indicated that at all ages greater than 1 year, females are larger than males. The mean length difference favouring females is approximately 6 cm. A multiple regression equation was derived that permits estimation of body weight from length and girth measurements. Relative weights and growth coefficients of several tissues and organs are recorded, and discussed in relation to similar data from other species of marine mammals.

Download Full-text

Pressure-volume characteristics of aortas of harbor and Weddell seals

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1986.251.1.r174 ◽

1986 ◽

Vol 251 (1) ◽

pp. R174-R180 ◽

Cited By ~ 3

Author(s):

E. A. Rhode ◽

R. Elsner ◽

T. M. Peterson ◽

K. B. Campbell ◽

W. Spangler

Keyword(s):

Mechanical Properties ◽

Stroke Volume ◽

Thoracic Aorta ◽

Marine Mammals ◽

Wall Stress ◽

Stroke Work ◽

Descending Thoracic Aorta ◽

Weddell Seals ◽

Terrestrial Mammals ◽

Total Potential

The mechanical properties of the radially enlarged proximal segment of the aorta of diving marine mammals was studied on 15 excised aortas of harbor seals and five aortas of Weddell seals. This was done by recording static pressure-volume relationships for the whole thoracic aorta, the aortic bulb, and the descending thoracic aorta and passive length-tension measurements of aortic strips. Aortic bulb volume distensibility was found to be much greater than that of the descending thoracic aorta or of an equivalent aortic segment of terrestrial mammals. The consequences were that the total potential energy and volume that may be stored within the aortic bulb is very large, with a capacity for storage of the stroke work of more than two normal heart beats and a volume of more than three times normal stroke volume. The aortic bulb has an average radius and wall thickness twice that of the descending aorta, but at any level of distension the wall stress (g/cm2) is the same throughout. The static mechanical properties of aortic strips from the bulb and descending thoracic aortas were not markedly different, so that the differences in the pressure-volume relationships are explained by differences in geometry of the two sections. The expanded aortic bulb functions through energy and volume storage actions and through uncoupling actions to maintain arterial pressures and stroke volume at near predive levels during a dive.

Download Full-text

Animal-Borne Instrumentation Systems and the Animals that Bear Them: Then (1939) and Now (2007)

Marine Technology Society Journal ◽

10.4031/002533207787441935 ◽

2007 ◽

Vol 41 (4) ◽

pp. 6-8 ◽

Cited By ~ 5

Author(s):

Gerald Kooyman

Keyword(s):

Loggerhead Turtle ◽

Video Camera ◽

Weddell Seal ◽

Gps Tracking ◽

Major Step ◽

Mcmurdo Sound ◽

Weddell Seals ◽

History Of ◽

Archival Systems ◽

Microprocessor Technology

The history of animal-borne instrumentation is reviewed from the first basic depth gauge invented in the late 1800s, to the complex animal-borne imagery and archival systems of the present day. A major breakthrough occurred in 1964 when the first time-depth recorder was deployed on a Weddell Seal in McMurdo Sound, Antarctica. The next phase in the study of animals at sea was the use of microprocessors as archival recorders in the mid-1980s. These also were first attached to Weddell seals in McMurdo Sound. Microprocessor technology made possible the next major step of attaching a video camera housed in a submersible case (Crittercam) to a loggerhead turtle. Since the 1990s the field of “Biologging” has flourished, with new additions of satellite and GPS tracking, and resulted in three major international symposiums in the past four years (2003-2007).

Download Full-text

Metabolic adjustments to breath holding in higher vertebrates

Canadian Journal of Zoology ◽

10.1139/z89-425 ◽

1989 ◽

Vol 67 (12) ◽

pp. 3024-3031 ◽

Cited By ~ 2

Author(s):

P. J. Butler

Keyword(s):

Marine Mammals ◽

Lactate Production ◽

Weddell Seal ◽

Specific Dynamic Action ◽

The Body ◽

Breath Holding ◽

Reduced Body ◽

Key Factor ◽

Reduced Rate ◽

Anaerobic Production

There is substantial behavioural and physiological evidence to suggest that most feeding dives by aquatic birds and mammals are aerobic in nature, with no net production of lactate. Any increase in lactate production is matched by increased removal. This does not mean, however, that there are no cardiovascular adjustments associated with such dives. Nonactive parts of the body (including the large pectoral muscles in diving ducks) may be hypoperfused and consume oxygen at a reduced rate. For example, in marine mammals, such as the Weddell seal, reduced perfusion of the gut during a feeding period (which can last for up to 12 h) would reduce the energy expenditure associated with the digestion and assimilation of food (specific dynamic action). Reperfusion during the nonfeeding period would contribute to an unusually high "resting" oxygen uptake. Although some tissues in seals at least can tolerate periods of ischaemia, there is no evidence to suggest that enhanced anaerobic production of ATP is a key factor in the survival of marine mammals during unusually long periods underwater. There may, in fact, be an overall reduction in the ATP requirements of certain tissues, possibly as a result of a reduction in the permeability of cell membranes to some ions, but most certainly as a result of reduced body temperature. During relatively long dives, lactate production eventually exceeds its rate of removal and it accumulates. Precisely what occurs in the muscles is not known. One suggestion is that periods of vasoconstriction are interrupted by vasodilatation, when the oxygen stores are replaced.

Download Full-text

Effects of Aging on Type II Muscle Fibers: A Systematic Review of the Literature

Journal of Aging and Physical Activity ◽

10.1123/japa.15.3.336 ◽

2007 ◽

Vol 15 (3) ◽

pp. 336-348 ◽

Cited By ~ 46

Author(s):

Florian Brunner ◽

Annina Schmid ◽

Ali Sheikhzadeh ◽

Margareta Nordin ◽

Jangwhon Yoon ◽

...

Keyword(s):

Systematic Review ◽

Skeletal Muscles ◽

Morphological Changes ◽

Fiber Type ◽

Muscle Fibers ◽

Type Ii ◽

Review Of The Literature ◽

Effects Of Aging ◽

Complex Phenomena ◽

Human Skeletal Muscles

The authors conducted a systematic review of the literature for scientific articles in selected databases to determine the effects of aging on Type II muscle fibers in human skeletal muscles. They found that aging of Type II muscle fibers is primarily associated with a loss of fibers and a decrease in fiber size. Morphological changes with increasing age particularly included Type II fiber grouping. There is conflicting evidence regarding the change of proportion of Type II fibers. Type II muscle fibers seem to play an important role in the aging process of human skeletal muscles. According to this literature review, loss of fibers, decrease in size, and fiber-type grouping represent major quantitative changes. Because the process of aging involves various complex phenomena such as fiber-type coexpression, however, it seems difficult to assign those changes solely to a specific fiber type.

Download Full-text

Load-matched acute and chronic exercise induce changes in mitochondrial biogenesis and metabolic markers

Applied Physiology Nutrition and Metabolism ◽

10.1139/apnm-2020-1053 ◽

2021 ◽

Author(s):

Natalia Almeida Rodrigues ◽

Claudio Alexandre Gobatto ◽

Lucas Dantas Maia Forte ◽

Filipe Antônio de Barros Sousa ◽

Adriana Souza Torsoni ◽

...

Keyword(s):

Aerobic Capacity ◽

Skeletal Muscles ◽

Acute Exercise ◽

Citrate Synthase ◽

Liver Glycogen ◽

Chronic Exercise ◽

Total Load ◽

Metabolic Markers ◽

Target Proteins ◽

Glycogen Stores

We investigated the effects of the acute and chronic exercise, prescribed in different intensity zones, but with total load-matched on mitochondrial markers (COX-IV, Tfam, and citrate synthase (CS) activity in skeletal muscles, heart, and liver), glycogen stores, aerobic capacity and anaerobic index in swimming rats. For this, two experimental designs were performed (acute and chronic efforts). Load-matched exercises were prescribed below and above and on the anaerobic threshold (AnT), determined by the Lactate Minimum test. In chronic programs, two training prescription strategies were assessed (monotonous and linear periodized model). Results show changes in glycogen stores but no modification in the COX-IV and Tfam contents after acute exercises. In the chronic protocols, COX-IV and Tfam proteins and CS adaptations were intensity and tissue dependents. Monotonous training promoted better adaptations than the periodized model. Training at 80% of the AnT improved both performance variables, emphasizing the anaerobic index, concomitant to CS and COX-IV improvement (soleus muscle). The aerobic capacity and CS activity (gastrocnemius) were increased after 120% AnT training. In conclusion, acute exercise protocol did not promote responses in mitochondrial target proteins. An intensity and tissue dependence are reported in the chronic protocols, highlighting training at 80 and 120% of the AnT. Novelty: • Load-matched acute exercise did not enhance COX-IV and Tfam contents in skeletal muscles, heart, and liver. • In chronic exercise, COX-IV, Tfam, and citrate synthase activity adaptations were intensity and tissue dependents. •Monotonous training was more efficient than the periodized linear model in adaptations of target proteins and enzymatic activity.

Download Full-text

Muscle capillary supply in harbor seals

Journal of Applied Physiology ◽

10.1152/jappl.2001.90.5.1919 ◽

2001 ◽

Vol 90 (5) ◽

pp. 1919-1926 ◽

Cited By ~ 15

Author(s):

Shane B. Kanatous ◽

Robert Elsner ◽

Odile Mathieu-Costello

Keyword(s):

Surface Area ◽

Skeletal Muscles ◽

Harbor Seals ◽

Capillary Length ◽

Capillary Supply ◽

Terrestrial Mammals ◽

Lower Volume ◽

Fiber Number ◽

Mitochondrial Volume ◽

Comparable Size

The purpose of this study was to examine muscle capillary supply in harbor seals. Locomotory and nonlocomotory muscles of four harbor seals (mass = 17.5–41 kg) were glutaraldehyde-perfusion fixed and samples processed for electron microscopy and analyzed by morphometry. Capillary-to-fiber number and surface ratios were 0.81 ± 0.05 and 0.16 ± 0.01, respectively. Capillary length and surface area per volume of muscle fiber were 1,495 ± 83 mm/mm3 and 22.4 ± 1.6 mm2/mm3, respectively. In the locomotory muscles, we measured capillary length and surface area per volume mitochondria (20.1 ± 1.7 km/ml and 2,531 ± 440 cm2/ml). All these values are 1.5–3 times lower than in muscles with similar or lower volume densities of mitochondria in dogs of comparable size. Compared with terrestrial mammals, the skeletal muscles of harbor seals do not match their increased aerobic enzyme capacities and mitochondrial volume densities with greater muscle capillary supply. They have a smaller capillary-to-fiber interface and capillary supply per fiber mitochondrial volume than terrestrial mammals of comparable size.

Download Full-text