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1978
Ponganis, PJ, Pierce RW.  1978.  Muscle metabolic profiles and fiber-type composition in some marine mammals. Comparative Biochemistry and Physiology B-Biochemistry & Molecular Biology. 59:99-102.   10.1016/0305-0491(78)90187-6   AbstractWebsite

1. Hexokinase, lactate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase, and malate dehydrogenase activities as well as fiber type composition were determined in skeletal muscles of the California sea lion (Zalophus californianus), the sea otter (Enhydra lutris), and the Pacific white-sided dolphin (Lagenorhynchusobliquidens).2. The subcutaneous muscle of the sea lion had intermediate glycolytic and oxidative enzyme activities.3. The locomotory muscles examined in the otter and porpoise did not contain a single predominant fiber type, but did have a well developed oxidative as well as glycolytic metabolic capacity.

1987
Goforth, H, Ponganis PJ, Eggerton E.  1987.  Glycogenolytic responses and force production characteristics of a bottlenose dolphin (Tursiops truncatus). Seventh biennial Conference on the Biology of Marine Mammals, abstracts, December 5-9, 1987, Miami, Florida. :1., Miami, FL: s.n. Abstract
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1989
Ponganis, PJ, Gentry RL, Ponganis EP, Ponganis K.  1989.  Analysis of swimming velocity in deep and shallow dives of two northern fur seals, Callorhinus ursinus. Proceedings of the Eighth Biennial Conference on the Biology of Marine Mammals. , Pacific Grove, Calif. Abstract
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Eckert, SA, Eckert KL, Ponganis P, Kooyman GL.  1989.  Diving and foraging behavior of leatherback sea turtles (Dermochelys coriacea). Canadian Journal of Zoology-Revue Canadienne De Zoologie. 67:2834-2840.   10.1139/z89-399   AbstractWebsite

Remote time–depth recorders (TDR) were deployed on six gravid leatherbacks nesting on Sandy Point, St. Croix. Dive behavior was monitored continuously for each turtle during internesting intervals ranging from 9 to 11 days. Dive duration averaged 9.9 min/dive (SD = 5.3, n = 5096); mean depth was 61.6 m (SD = 59.1, n = 5096). One turtle dived twice beyond the range of her TDR to depths we estimate >1000 m. Postdive surfacing intervals averaged 4.9 min/dive (SD = 13.1, n = 5090). Differences in mean dive depth, dive duration, and surface intervals among turtles were not attributable to differences in body size (length or mass). Distinct diel periodicity was observed in dive behavior; submergence intervals were longest at dawn, declined throughout the day, and were shortest at dusk. Night dives (19:00–04:59) were shorter, shallower, and more frequent than day dives (05:00–18:59). Dive depth was less variable at night than during the day. The dive pattern suggests nocturnal foraging within the deep scattering layer, a hypothesis that is corroborated by seasonal weight loss data.

1990
Kooyman, G, Ponganis PJ.  1990.  Behavior and physiology of diving in emperor and king penguins. Penguin biology. ( Davis L, Darby JT, Eds.).:14., San Diego: Academic Press Abstract
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Ponganis, PJ, Kooyman GL, Zornow MH, Castellini MA, Croll DA.  1990.  Cardiac output and stroke volume in swimming harbor seals. Journal of Comparative Physiology B-Biochemical Systemic and Environmental Physiology. 160:473-482.   10.1007/BF00258974   AbstractWebsite

Cardiac output was measured by the thermodilution method in three young harbor seals, at rest and while swimming up to the maximum effort for which they could be trained. Stroke volume was determined by counting heart rate simultaneously with determination of cardiac output. Cardiac outputs varied widely between surface breathing (7.8 ml.kg-1.s-1) and breath-holding while swimming under water (1.8 ml.kg-1.s-1). Stroke volume while at the surface was almost twice the volume while submerged. Surface cardiac output was always near maximal despite work effort, whereas submerged cardiac output gradually increased at higher work efforts. The cardiovascular performance of seals at the maximum MO2 we could induce from them is equivalent to that of the domestic goat.

Ponganis, PJ, Kooyman GL.  1990.  Diving physiology of penguins. Acta XX Congressus Internationalis Ornithologici, Christchurch, New Zealand, 2-9 December 1990. ( Butler PJ, Jones DR, Eds.).:6., Wellington, N.Z.: New Zealand Ornithological Congress Trust Board Abstract
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Ponganis, PJ, Ponganis EP, Ponganis KV, Kooyman GL, Gentry RL, Trillmich F.  1990.  Swimming velocities in otariids. Canadian Journal of Zoology-Revue Canadienne De Zoologie. 68:2105-2112.   10.1139/z90-293   AbstractWebsite

Velocities during surface swimming and diving were measured with microprocessor recorders in four otariid species: northern fur seals (Callorhinusursinus), Galapagos sea lions (Zalophuscalifornianuswollebaeki), Galapagos fur seals (Arctocephalusgalapagoensis), and Hooker's sea lions (Phocarctoshookeri). Mean surface swimming velocities ranged from 0.6 to 1.9 m/s. Transit distances to feeding sites (1.2–90 km) were calculated using these velocities. Dive velocities, recorded every 15 s, ranged from 0.9 to 1.9 m/s. These velocities were consistent with calculated minimal cost of transport velocities in the smaller species. Using time partitioning, the metabolic cost of a northern fur seal foraging trip is estimated on the basis of recorded velocities and their calculated energy costs. This value is within 6% of that previously made with doubly labeled water techniques.

1991
Ponganis, PJ, Kooyman GL, Zornow MH.  1991.  Cardiac output in swimming California sea lions, Zalophus californianus. Physiological Zoology. 64:1296-1306. AbstractWebsite

Cardiac output was determined by the thermodilution technique in three California sea lions while resting and while swimming. Metabolic rates increased seven-to ninefold above resting rates during maximal exercise. While the sea lions were at rest, stroke volume was also determined by simultaneously counting heart rate during cardiac output determinations. At rest, cardiac output (2.5-3.0 mL kg-1s-1) and stroke volume (2 mL kg-1) were similar to those of harbor seals and terrestrial mammals of similar mass. During exercise, mean cardiac output increased linearly with work load and surface/submerged intervals were short and frequent. The exercise capacity of swimming sea lions appears similar to that of harbor seals, but the exercise response resembles that of terrestrial mammals more than that of harbor seals.

1992
Newsome, LR, Ponganis PJ, Reichman R, Nakaji N, Jaski B, Haltley M.  1992.  Portable percutaneous cardiopulmonary bypass: use in supported coronary angioplasty, aortic valvuloplasty, and cardiac arrest. Journal of Cardiothoracic and Vascular Anesthesia. 6:328-331.   10.1016/1053-0770(92)90151-V   Abstract

Portable cardiopulmonary bypass (CPB) systems consisting of a battery source and charger, centrifugal pump, hollow-fiber oxygenator, pump tubing, and large-bore thin-walled femoral arterial and venous cannulae have been commercially available for the past few years. Modifications of the Seldinger technique to allow percutaneous placement facilitate the expeditious institution of CPB in virtually any hospital setting.‘” As a result of this new technology, “supported” percutaneous transluminal coronary angioplasty (PTCA) and aortic valvuloplasty (AVP), which use the prophylactic institution of percutaneous CPB prior to the beginning of these procedures, were reported in 1990. Additionally, these portable systems have been used at various medical centers to help resuscitate patients suffering from cardiac arrest from a variety of causes. Two case histories representative of the use of such a system in both scenarios and including some anesthetic considerations for the use of such systems, specifically in supported angioplasties, are reported. In addition, the authors’ total experience with portable CPB is described.

Kooyman, GL, Ponganis PJ, Castellini MA, Ponganis EP, Ponganis KV, Thorson PH, Eckert SA, Lemaho Y.  1992.  Heart rates and swim speeds of Emperor penguins diving under sea ice. Journal of Experimental Biology. 165:161-180. AbstractWebsite

Heart rate during overnight rest and while diving were recorded from five emperor penguins with a microprocessor-controlled submersible recorder. Heart rate, cardiac output and stroke volume were also measured in two resting emperor penguins using standard electrocardiography and thermodilution measurements. Swim velocities from eight birds were obtained with the submersible recorder. The resting average of the mean heart rates was 72 beats min-1. Diving heart rates were about 15% lower than resting rates. Cardiac outputs of 1.9-2.9 ml kg-1 s-1 and stroke volumes of 1.6-2.7 ml kg-1 were similar to values recorded from mammals of the same body mass. Swim velocities averaged 3 m s-1. The swim speeds and heart rates suggest that muscle O2 depletion must occur frequently: therefore, many dives require a significant energy contribution from anaerobic glycolysis.

Castellini, MA, Kooyman GL, Ponganis PJ.  1992.  Metabolic rates of freely diving Weddell seals: correlations with oxygen stores, swim velocity and diving duration. Journal of Experimental Biology. 165:181-194. AbstractWebsite

The metabolic rates of freely diving Weddell seals were measured using modern methods of on-line computer analysis coupled to oxygen consumption instrumentation. Oxygen consumption values were collected during sleep, resting periods while awake and during diving periods with the seals breathing at the surface of the water in an experimental sea-ice hole in Antarctica. Oxygen consumption during diving was not elevated over resting values but was statistically about 1.5 times greater than sleeping values. The metabolic rate of diving declined with increasing dive duration, but there was no significant difference between resting rates and rates in dives lasting up to 82 min. Swimming speed, measured with a microprocessor velocity recorder, was constant in each animal. Calculations of the aerobic dive limit of these seals were made from the oxygen consumption values and demonstrated that most dives were within this theoretical limit. The results indicate that the cost of diving is remarkably low in Weddell seals relative to other diving mammals and birds.

Ponganis, PJ, Kooyman GL, Sartoris D, Jobsis P.  1992.  Pinniped splenic volumes. American Journal of Physiology. 262:R322-R325. AbstractWebsite

Splenic volume was measured by computerized axial tomography in three harbor seals (Phoca vitulina) and two California sea lions (Zalophus californianus). Volumes ranged from 228 to 679 ml, representing 0.8-3.0% of calculated percentage body mass. Despite possible variation in the state of splenic contraction during the examination, these values are in the upper range of reported mammalian splenic volumes (as % of body mass). This reinforces the pinniped splenic erythrocyte storage concept.

Ponganis, PJ, Gentry RL, Ponganis EP, Ponganis KV.  1992.  Analysis of swim velocities during deep and shallow dives of two northern fur seals, Callorhinus ursinus. Marine Mammal Science. 8:69-75.   10.1111/j.1748-7692.1992.tb00126.x   AbstractWebsite

Swim velocities at 15-sec intervals and maximum depth per dive were recorded by microprocessor units on two "mixed diver" adult female northern fur seals during summer foraging trips. These records allowed comparison of swim velocities of deep (> 75 m) and shallow (< 75 m) dives. Deep dives averaged 120 m depth and 3 min duration; shallow dives averaged 30 m and 1.2 min. Mean swim velocities on deep dives were 1.8 and 1.5 m/ sec for the two animals; mean swim velocities on shallow dives were 1.5 and 1.2 m/sec. The number of minutes per hour spent diving during the deep and shallow dive patterns were 11 and 27 min, respectively. Swim velocity, and hence, relative metabolic rate, did not account for the differences in dive durations between deep and shallow dives. The long surface durations associated with deep dives, and estimates of metabolic rates for the observed swim velocities, suggest that deep dives involve significant anaerobic metabolism.

Ancel, A, Kooyman GL, Ponganis PJ, Gendner JP, Lignon J, Mestre X, Huin N, Thorson PH, Robisson P, Lemaho Y.  1992.  Foraging behaviour of emperor penguins as a resource detector in winter and summer. Nature. 360:336-339.   10.1038/360336a0   AbstractWebsite

The emperor penguin (Aptenodytes forsteri), which feeds only at sea, is restricted to the higher latitudes of the antarctic sea-ice habitat1-3. It breeds on the winter fast ice when temperatures are -30-degrees-C and high winds are frequent3. Assuming entirely the task of incubating the single egg, the male fasts for about 120 days in the most severe conditions. When it is relieved by the female around hatching time, the distance between the colony and the open sea may be 100 km or more4,5, but where emperors go to forage at that time or during the summer is unknown. The polynias are areas of open water in sea-ice and during winter, with the under-ice habitats at any time of the year, they are among the most difficult of all Antarctic areas to sample. Here we monitor by satellite the routes taken by emperor penguins for foraging and compare them with satellite images of sea-ice. Winter birds walking over fast ice travelled up to 296 km to feed in polynias, whereas those swimming in light pack-ice travelled as far as 895 km from the breeding colony. One record of diving showed that although most dives are to mid-water depths, some are near the bottom. Obtaining such detailed information on foraging in emperor penguins means that this bird now offers a unique opportunity to investigate the Antarctic sea-ice habitat.

1993
Ponganis, PJ, Kooyman GL, Castellini MA, Ponganis EP, Ponganis KV.  1993.  Muscle temperature and swim velocity profiles during diving in a Weddell seal, Leptonychotes weddellii. Journal of Experimental Biology. 183:341-346. AbstractWebsite

Locomotory muscle temperature and swim velocity profiles of an adult Weddell seal were recorded over a 21 h period. The highest temperatures occurred during a prolonged surface period (mean 37.3-degrees-C, S.D. 0.16-degrees-C). Muscle temperature averaged 36.8 and 36.6-degrees-C (S.D. 0.25-degrees-C, 0.19-degrees-C) during two dive bouts and showed no consistent fluctuations between dive and interdive surface intervals. Swim velocities were also constant, near 1.3 m s-1. These data indicate that past records of low aortic temperatures (35-degrees-C) during and after prolonged dives are not indicative of whole-body temperature changes, and that muscle temperature, even during dives as long as 45 min, remains near 37-degrees-C.

Ponganis, PJ, Kooyman GL, Castellini MA.  1993.  Determinants of the aerobic dive limit of Weddell seals: analysis of diving metabolic rates, postdive end tidal PO2's, and blood and muscle oxygen stores. Physiological Zoology. 66:732-749. AbstractWebsite

The mean aerobic dive limit (ADL) for Weddell seals was calculated from data collected on diving metabolic rates (VO2) and blood and muscle O2 stores. Mean diving VO2 of adult seals during predominantly exploratory dive patterns was 4.5 mL O2 kg-1 min-1; mean VO2 of a subadult seal engaged in foraging dive bouts was 8.5 mL O2 kg-1 min-1. The adult value was 30% greater than that used in past ADL calculations. Mean plasma volume was 7% body mass (BM); blood volume calculated with the highest hematocrit (Hct) observed (66) was 21% BM. Hemoglobin concentration at such an Hct was 26% by weight. End tidal PO2 (pre- and postdive) justified the use of 95% and 20% arterial O2 saturations in the blood O2 store calculation. Total blood O2 stores were 50% greater than those used in past ADL calculations. Mean myoglobin concentration (5.4% by weight) and more recent anatomical estimates of muscle mass yielded a 35% increase in muscle O2 stores. The mean estimated ADL for a 450-kg seal calculated with these new data was 19.1 min, 2.3 min greater than in past calculations and only 1 min less than the 20-min inflection point of the curve of dive duration versus postdive lactic acid appearance. For the subadult engaged in foraging dives, the mean estimated ADL was about 9 min, again quite similar to past ADL calculations.

1994
Kooyman, GL, Ponganis PJ.  1994.  Emperor penguin oxygen consumption, heart rate and plasma lactate levels during graded swimming exercise. Journal of Experimental Biology. 195:199-209. AbstractWebsite

Oxygen consumption (V-O2), heart rate and blood chemistry were measured in four emperor penguins, Aptenodytes forsteri (Gray), during graded swimming exercise. The maximum V-O2, obtained, 52ml O-2 kg(-1) min(-1), was 7.8 times the measured resting V-O2 of 6.7 ml O-2 kg(-1) min(-1) and 9.1 times the predicted resting V-O2. As the swimming effort rose, a linear increase in surface and submerged heart rates (fH) occurred. The highest average maximum surface and submersion heart rates of any bird were 213 and 210 beats min(-1), respectively. No increase in plasma lactate concentrations occurred until V-O2 was greater than 25 ml O-2 kg(-1) min(-1). At the highest V-O2 values measured, plasma lactate concentration reached 9.4 mmol l(-1). In comparison with other animals of approximately the same mass, the aerobic capacity of the emperor penguin is less than those of the emu and dog but about the same as those of the seal, sea lion and domestic goat. For aquatic animals, a low aerobic capacity seems to be consistent with the needs of parsimonious oxygen utilization while breath-holding.

1995
Ponganis, PJ, Kooyman GL, Castellini MA.  1995.  Multiple sightings of Arnouxs beaked whales along the Victoria Land coast. Marine Mammal Science. 11:247-250.   10.1111/j.1748-7692.1995.tb00523.x   AbstractWebsite
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1997
Ponganis, PJ, Kooyman GL, Baranov EA, Thorson PH, Stewart BS.  1997.  The aerobic submersion limit of Baikal seals, Phoca sibirica. Canadian Journal of Zoology-Revue Canadienne De Zoologie. 75:1323-1327.   10.1139/z97-756   AbstractWebsite

An aerobic dive limit (ADL), the diving duration beyond which postdive lactate concentration increases above the resting level, has been estimated theoretically for many species. Such calculations have been based on an oxygen store/diving metabolic rate (MR) equation. Until now, an ADL has been determined empirically from measurements of blood lactate concentration only in the Weddell seal, Leptonychotes weddellii. We measured post-submergence plasma lactate concentrations during spontaneous voluntary submersions of three captive adult Baikal seals (Phoca sibirica). Two-phase regression analysis revealed a transition in the lactate concentration - submersion duration relationship after the animal had been diving for 15 min. Data collected in prior studies on oxygen stores and submersion metabolic rates of Baikal seals yielded a calculated aerobic limit of 16 min. As in Weddell seals, the empirically determined aerobic limit was very similar to the theoretical limit. Furthermore, most diving durations recorded during recent studies of free-ranging Baikal seals are under this limit. These data support the concept of an ADL and its estimation by means of an oxygen store/diving MR calculation.

Ponganis, PJ, Kooyman GL, Winter LM, Starke LN.  1997.  Heart rate and plasma lactate responses during submerged swimming and trained diving in California sea lions, Zalophus californianus. Journal of Comparative Physiology B-Biochemical Systemic and Environmental Physiology. 167:9-16.   10.1007/s003600050042   AbstractWebsite

California sea lions, Zalophus californianus, were trained to elicit maximum voluntary breath holds during stationary underwater targeting, submerged swimming, and trained diving. Lowest heart rate during rest periods was 57 bpm. The heart rate profiles in all three protocols were dominated by a bradycardia of 20-50 bpm, and demonstrated that otariid diving heart rates were at or below resting heart rate. Venous blood samples were collected after submerged swimming periods of 1-3 min. Plasma lactate began to increase only after 2.3-min submersions. This rise in lactate and our inability to train sea lions to dive or swim submerged for periods longer than 3 min lead us to conclude that an aerobic limit had been reached. Due to the similarity of heart rate responses and swimming velocities recorded during submerged swimming and trained diving, this 2.3-min limit should approximate the aerobic dive limit in these 40-kg sea lions. Total body O-2 stores, based on measurements of blood and muscle O-2 stores in these animals, and prior lung O-2 Store analyses, were 37-43 ml O-2 kg(-1). The aerobic dive limit, calculated with these O-2 stores and prior measurements of at-sea metabolic rates of sea lions, is 1.8-2 min, similar to that measured by the change in post-submersion lactate concentration.

Ponganis, PJ, Costello ML, Starke LN, MathieuCostello O, Kooyman GL.  1997.  Structural and biochemical characteristics of locomotory muscles of emperor penguins, Aptenodytes forsteri. Respiration Physiology. 109:73-80.   10.1016/s0034-5687(97)84031-5   AbstractWebsite

Structural and biochemical characteristics of the primary muscles used for swimming (pectoralis, PEC and supracoracoideus, SC) were compared to those of leg muscles in emperor penguins (Aptenodytes forsteri). The mass of PEG-SC was four times that of the leg musculature, and mitochondrial volume density in PEC and SC (4%) was two-thirds that in sartorius (S) and gastrocnemius. The differences in muscle mass and mitochondrial density yielded a 2.2-fold greater total mitochondrial content in PEG-SC than leg muscles, which appears to account for the 1.8-fold greater whole-body highest oxygen consumption previously recorded in emperor penguins during swimming compared to walking. Calculation of maximal mitochondrial O-2 consumption in PEG-SC and leg muscle yielded values of 5.8-6.9 mi O-2 ml(-1) min(-1), which are similar to those in locomotory muscles of most mammals and birds. A distinct feature of emperor penguin muscle was its myoglobin content, with concentrations in PEG-SC (6.4 g 100 g(-1)) among the highest measured in any species. This resulted in a PEG-SC O-2 store greater than that of the entire blood. In addition, ratios of myoglobin content to mitochondrial volume density and to citrate synthase activity were 4.4 and 2.5 times greater in PEG than in S, indicative of the significant role of myoglobin in the adaptation of muscle to cardiovascular adjustments during diving. (C) 1997 Elsevier Science B.V.

Ponganis, PJ, Kooyman GL, Starke LN, Kooyman CA, Kooyman TG.  1997.  Post-dive blood lactate concentrations in emperor penguins, Aptenodytes forsteri. Journal of Experimental Biology. 200:1623-1626. AbstractWebsite

In order to determine an aerobic diving limit (ADL) in emperor penguins (Aptenodytes forsteri), post-dive blood lactate concentrations were measured in penguins foraging at an isolated sea ice hole. Resting lactate concentrations were 1.2-2.7 mmol l(-1). Serial samples revealed that lactate level usually peaked within 5 min after dives and that 7-12 min was required for lactate concentrations to decrease from 5-8 mmol l(-1) to less than 2.5 mmol l(-1). Post-dive lactate level was not elevated above 3 mmol l(-1) for dives shorter than 5 min. Two-phase regression analysis revealed a transition at 5.6 min in the post-dive lactate level versus diving duration relationship. All dives longer than 7 min were associated with lactate concentrations greater than 5 mmol l(-1). We conclude that the ADL in emperor penguins ranges between 5 and 7 min. These are the first determinations of post-dive lactate concentrations in any free-diving bird and are currently the only physiological assessment of an ADL in an avian species.

Kooyman, GL, Ponganis PJ.  1997.  The challenges of diving to depth. American Scientist. 85:530-539. AbstractWebsite
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1998
Kooyman, GL, Ponganis PJ.  1998.  The physiological basis of diving to depth: Birds and mammals. Annual Review of Physiology. 60:19-32.   10.1146/annurev.physiol.60.1.19   AbstractWebsite

There is wide diversity in the animals that dive to depth and in the distribution of their body oxygen stores. A hallmark of animals diving to depth is a substantial elevation of muscle myoglobin concentration. In deep divers, more than 80% of the oxygen store is in the blood and muscles. How these oxygen stores are managed, particularly within muscle, is unclear. The aerobic endurance of four species has now been measured. These measurements provide a standard for other species in which the limits cannot be measured. Diving to depth requires several adaptations to the effects of pressure. In mammals, one adaptation is lung collapse at shallow depths, which limits absorption of nitrogen. Blood Nz levels remain below the threshold for decompression sickness. No such adaptive model is known for birds. There appear to be two diving strategies used by animals that dive to depth. Seals, for example, seldom rely on anaerobic metabolism. Birds, on the other hand, frequently rely on anaerobic metabolism to exploit prey-rich depths otherwise unavailable to them.