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Costa DP, Favilla AB. Field physiology in the aquatic realm: ecological energetics and diving behavior provide context for elucidating patterns and deviations. J Exp Biol 2023; 226:jeb245832. [PMID: 37843467 DOI: 10.1242/jeb.245832] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2023]
Abstract
Comparative physiology has developed a rich understanding of the physiological adaptations of organisms, from microbes to megafauna. Despite extreme differences in size and a diversity of habitats, general patterns are observed in their physiological adaptations. Yet, many organisms deviate from the general patterns, providing an opportunity to understand the importance of ecology in determining the evolution of unusual adaptations. Aquatic air-breathing vertebrates provide unique study systems in which the interplay between ecology, physiology and behavior is most evident. They must perform breath-hold dives to obtain food underwater, which imposes a physiological constraint on their foraging time as they must resurface to breathe. This separation of two critical resources has led researchers to investigate these organisms' physiological adaptations and trade-offs. Addressing such questions on large marine animals is best done in the field, given the difficulty of replicating the environment of these animals in the lab. This Review examines the long history of research on diving physiology and behavior. We show how innovative technology and the careful selection of research animals have provided a holistic understanding of diving mammals' physiology, behavior and ecology. We explore the role of the aerobic diving limit, body size, oxygen stores, prey distribution and metabolism. We then identify gaps in our knowledge and suggest areas for future research, pointing out how this research will help conserve these unique animals.
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Affiliation(s)
- Daniel P Costa
- Institute of Marine Sciences, Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA 95060, USA
| | - Arina B Favilla
- Institute of Marine Sciences, Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA 95060, USA
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2
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Iron mobilization during lactation reduces oxygen stores in a diving mammal. Nat Commun 2022; 13:4322. [PMID: 35918323 PMCID: PMC9345918 DOI: 10.1038/s41467-022-31863-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 07/06/2022] [Indexed: 11/22/2022] Open
Abstract
The profound impacts that maternal provisioning of finite energy resources has on offspring survival have been extensively studied across mammals. This study shows that in addition to calories, high hemoprotein concentrations in diving mammals necessitates exceptional female-to-pup iron transfer. Numerous indices of iron mobilization (ferritin, serum iron, total-iron-binding-capacity, transferrin saturation) were significantly elevated during lactation in adult female Weddell seals (Leptonychotes weddellii), but not in skip-breeders. Iron was mobilized from endogenous stores for incorporation into the Weddell seal’s milk at concentrations up to 100× higher than terrestrial mammals. Such high rates of iron offload to offspring drew from the female’s own heme stores and led to compromised physiologic dive capacities (hemoglobin, myoglobin, and total body oxygen stores) after weaning their pups, which was further reflected in shorter dive durations. We demonstrate that lactational iron transfer shapes physiologic dive thresholds, identifying a cost of reproduction to a marine mammal. Here, the authors show that Weddell seal mothers mobilize endogenous iron stores during lactation to provide to pups, resulting in iron concentrations in milk 100x higher than terrestrial mammals. This was associated with reduced dive durations in the mother, a cost of reproduction.
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3
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Hooker SK, Andrews RD, Arnould JPY, Bester MN, Davis RW, Insley SJ, Gales NJ, Goldsworthy SD, McKnight JC. Fur seals do, but sea lions don't - cross taxa insights into exhalation during ascent from dives. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200219. [PMID: 34121462 PMCID: PMC8200655 DOI: 10.1098/rstb.2020.0219] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/07/2020] [Indexed: 11/12/2022] Open
Abstract
Management of gases during diving is not well understood across marine mammal species. Prior to diving, phocid (true) seals generally exhale, a behaviour thought to assist with the prevention of decompression sickness. Otariid seals (fur seals and sea lions) have a greater reliance on their lung oxygen stores, and inhale prior to diving. One otariid, the Antarctic fur seal (Arctocephalus gazella), then exhales during the final 50-85% of the return to the surface, which may prevent another gas management issue: shallow-water blackout. Here, we compare data collected from animal-attached tags (video cameras, hydrophones and conductivity sensors) deployed on a suite of otariid seal species to examine the ubiquity of ascent exhalations for this group. We find evidence for ascent exhalations across four fur seal species, but that such exhalations are absent for three sea lion species. Fur seals and sea lions are no longer genetically separated into distinct subfamilies, but are morphologically distinguished by the thick underfur layer of fur seals. Together with their smaller size and energetic dives, we suggest their air-filled fur might underlie the need to perform these exhalations, although whether to reduce buoyancy and ascent speed, for the avoidance of shallow-water blackout or to prevent other cardiovascular management issues in their diving remains unclear. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.
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Affiliation(s)
- Sascha K. Hooker
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, Fife KY16 8LB, UK
| | | | - John P. Y. Arnould
- School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia
| | - Marthán N. Bester
- Mammal Research Institute, University of Pretoria, Hatfield 0028, Gauteng, South Africa
| | - Randall W. Davis
- Department of Marine Biology, Texas A&M University, Galveston, TX 77553, USA
| | - Stephen J. Insley
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada, V8P 5C2
- Wildlife Conservation Society Canada, Whitehorse, Yukon Territory, Canada, Y1A 0E9
| | - Nick J. Gales
- Australian Antarctic Division, Kingston, Tasmania 7050, Australia
| | - Simon D. Goldsworthy
- South Australian Research and Development Institute, West Beach, South Australia 5024, Australia
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - J. Chris McKnight
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, Fife KY16 8LB, UK
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Enstipp MR, Bost CA, Le Bohec C, Chatelain N, Weimerskirch H, Handrich Y. The early life of king penguins: ontogeny of dive capacity and foraging behaviour in an expert diver. J Exp Biol 2021; 224:269166. [PMID: 34132335 DOI: 10.1242/jeb.242512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/24/2021] [Indexed: 11/20/2022]
Abstract
The period of emancipation in seabirds, when juveniles change from a terrestrial existence to a life at sea, is associated with many challenges. Apart from finding favourable foraging sites, they have to develop effective prey search patterns and physiological capacities that enable them to capture sufficient prey to meet their energetic needs. Animals that dive to forage, such as king penguins (Aptenodytes patagonicus), need to acquire an adequate breath-hold capacity, allowing them to locate and capture prey at depth. To investigate the ontogeny of their dive capacity and foraging performance, we implanted juvenile king penguins before their first departure to sea and also adult breeders with a data-logger recording pressure and temperature. We found that juvenile king penguins possess a remarkable dive capacity when leaving their natal colony, enabling them to conduct dives in excess of 100 m within their first week at sea. Despite this, juvenile dive/foraging performance, investigated in relation to dive depth, remained below the adult level throughout their first year at sea, probably reflecting physiological limitations as a result of incomplete maturation. A significantly shallower foraging depth of juveniles, particularly during their first 5 months at sea, could also indicate differences in foraging strategy and targeted prey. The initially greater wiggle rate suggests that juveniles fed opportunistically and also targeted different prey from adults and/or that many of the wiggles of juveniles reflect unsuccessful prey-capture attempts, indicating a lower foraging proficiency. After 5 months, this difference disappeared, suggesting sufficient physical maturation and improvement of juvenile foraging skills.
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Affiliation(s)
- Manfred R Enstipp
- Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France.,Centre d'Etudes Biologiques de Chizé, CNRS, UMR 7372, 79360 Villiers en Bois, France
| | - Charles-André Bost
- Centre d'Etudes Biologiques de Chizé, CNRS, UMR 7372, 79360 Villiers en Bois, France
| | - Céline Le Bohec
- Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France.,Centre Scientifique de Monaco, Département de Biologie Polaire, MC 98000, Monaco
| | - Nicolas Chatelain
- Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France
| | - Henri Weimerskirch
- Centre d'Etudes Biologiques de Chizé, CNRS, UMR 7372, 79360 Villiers en Bois, France
| | - Yves Handrich
- Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France
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5
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Ladds M, Rosen D, Gerlinsky C, Slip D, Harcourt R. Diving deep into trouble: the role of foraging strategy and morphology in adapting to a changing environment. CONSERVATION PHYSIOLOGY 2020; 8:coaa111. [PMID: 34168880 PMCID: PMC8218901 DOI: 10.1093/conphys/coaa111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 05/02/2020] [Accepted: 11/24/2020] [Indexed: 06/12/2023]
Abstract
Physiology places constraints on an animal's ability to forage and those unable to adapt to changing conditions may face increased challenges to reproduce and survive. As the global marine environment continues to change, small, air-breathing, endothermic marine predators such as otariids (fur seals and sea lions) and particularly females, who are constrained by central place foraging during breeding, may experience increased difficulties in successfully obtaining adequate food resources. We explored whether physiological limits of female otariids may be innately related to body morphology (fur seals vs sea lions) and/or dictate foraging strategies (epipelagic vs mesopelagic or benthic). We conducted a systematic review of the increased body of literature since the original reviews of Costa et al. (When does physiology limit the foraging behaviour of freely diving mammals? Int Congr Ser 2004;1275:359-366) and Arnould and Costa (Sea lions in drag, fur seals incognito: insights from the otariid deviants. In Sea Lions of the World Fairbanks. Alaska Sea Grant College Program, Alaska, USA, pp. 309-324, 2006) on behavioural (dive duration and depth) and physiological (total body oxygen stores and diving metabolic rates) parameters. We estimated calculated aerobic dive limit (cADL-estimated duration of aerobic dives) for species and used simulations to predict the proportion of dives that exceeded the cADL. We tested whether body morphology or foraging strategy was the primary predictor of these behavioural and physiological characteristics. We found that the foraging strategy compared to morphology was a better predictor of most parameters, including whether a species was more likely to exceed their cADL during a dive and the ratio of dive time to cADL. This suggests that benthic and mesopelagic divers are more likely to be foraging at their physiological capacity. For species operating near their physiological capacity (regularly exceeding their cADL), the ability to switch strategies is limited as the cost of foraging deeper and longer is disproportionally high, unless it is accompanied by physiological adaptations. It is proposed that some otariids may not have the ability to switch foraging strategies and so be unable adapt to a changing oceanic ecosystem.
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Affiliation(s)
- Monique Ladds
- Marine Ecosystems Team, Department of Conservation, Wellington 6011, New Zealand
- Marine Predator Research Group, Department of Biological Sciences,
Macquarie University, North Ryde 2113, Australia
| | - David Rosen
- Marine Mammal Research Unit, Institute for the Oceans and Fisheries,
University of British Columbia, Vancouver V6T 1Z4, Canada
| | - Carling Gerlinsky
- Marine Mammal Research Unit, Institute for the Oceans and Fisheries,
University of British Columbia, Vancouver V6T 1Z4, Canada
| | - David Slip
- Marine Predator Research Group, Department of Biological Sciences,
Macquarie University, North Ryde 2113, Australia
- Taronga Conservation Society Australia, Mosman 2088, Australia
| | - Robert Harcourt
- Marine Predator Research Group, Department of Biological Sciences,
Macquarie University, North Ryde 2113, Australia
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6
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Weitzner EL, Fanter CE, Hindle AG. Pinniped Ontogeny as a Window into the Comparative Physiology and Genomics of Hypoxia Tolerance. Integr Comp Biol 2020; 60:1414-1424. [PMID: 32559283 DOI: 10.1093/icb/icaa083] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Diving physiology has received considerable scientific attention as it is a central element of the extreme phenotype of marine mammals. Many scientific discoveries have illuminated physiological mechanisms supporting diving, such as massive, internally bound oxygen stores and dramatic cardiovascular regulation. However, the cellular and molecular mechanisms that support the diving phenotype remain mostly unexplored as logistic and legal restrictions limit the extent of scientific manipulation possible. With next-generation sequencing (NGS) tools becoming more widespread and cost-effective, there are new opportunities to explore the diving phenotype. Genomic investigations come with their own challenges, particularly those including cross-species comparisons. Studying the regulatory pathways that underlie diving mammal ontogeny could provide a window into the comparative physiology of hypoxia tolerance. Specifically, in pinnipeds, which shift from terrestrial pups to elite diving adults, there is potential to characterize the transcriptional, epigenetic, and posttranslational differences between contrasting phenotypes while leveraging a common genome. Here we review the current literature detailing the maturation of the diving phenotype in pinnipeds, which has primarily been explored via biomarkers of metabolic capability including antioxidants, muscle fiber typing, and key aerobic and anaerobic metabolic enzymes. We also discuss how NGS tools have been leveraged to study phenotypic shifts within species through ontogeny, and how this approach may be applied to investigate the biochemical and physiological mechanisms that develop as pups become elite diving adults. We conclude with a specific example of the Antarctic Weddell seal by overlapping protein biomarkers with gene regulatory microRNA datasets.
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Affiliation(s)
- Emma L Weitzner
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154, USA
| | - Cornelia E Fanter
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154, USA
| | - Allyson G Hindle
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV 89154, USA
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7
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Canei J, Nonclercq D. Morphological study of the integument and corporal skeletal muscles of two psammophilous members of Scincidae (Scincus scincus and Eumeces schneideri). J Morphol 2020; 282:230-246. [PMID: 33165963 PMCID: PMC7839682 DOI: 10.1002/jmor.21298] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 10/24/2020] [Accepted: 10/29/2020] [Indexed: 12/11/2022]
Abstract
Sand deserts are common biotopes on the earth's surface. Numerous morphological and physiological adaptations have appeared to cope with the peculiar conditions imposed by sandy substrates, such as abrasion, mechanical resistance and the potential low oxygen levels. The psammophilous scincids (Lepidosauria) Scincus scincus and Eumeces schneideri are among those. S. scincus is a species frequently used to study displacement inside a sandy substrate. E. schneideri is a species phylogenetically closely related to S. scincus with a similar lifestyle. The aims of this study focus on the morphology of the integument and the muscular system. Briefly, we describe interspecific differences at the superficial architecture of the scales pattern and the thickness of the integument. We highlight a high cellular turnover rate at the level of the basal germinal layer of the epidermis, which, we suggest, corresponds to an adaptation to cutaneous wear caused by abrasion. We demonstrate the presence of numerous cutaneous holocrine glands whose secretion probably plays a role in the flow of sand along the integument. Several strata of osteoderms strengthen the skin. We characterize the corporal (M. longissimus dorsi and M. rectus abdominus) and caudal muscular fibers using immunohistochemistry, and quantify them using morphometry. The musculature exhibits a high proportion of glycolytic fast fibers that allow rapid burying and are well adapted to this mechanically resistant and oxygen‐poor substrate. Oxidative slow fibers are low in abundance, less than 10% in S. scincus, but a little higher in E. schneideri.
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Affiliation(s)
- Jérôme Canei
- Laboratory of Histology, Biosciences Institute, Faculty of Medicine and Pharmacy, University of Mons, Mons, Belgium
| | - Denis Nonclercq
- Laboratory of Histology, Biosciences Institute, Faculty of Medicine and Pharmacy, University of Mons, Mons, Belgium
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8
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Shero MR, Reiser PJ, Simonitis L, Burns JM. Links between muscle phenotype and life history: differentiation of myosin heavy chain composition and muscle biochemistry in precocial and altricial pinniped pups. J Comp Physiol B 2019; 189:717-734. [DOI: 10.1007/s00360-019-01240-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 09/15/2019] [Accepted: 09/30/2019] [Indexed: 11/29/2022]
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9
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Thometz NM, Dearolf JL, Dunkin RC, Noren DP, Holt MM, Sims OC, Cathey BC, Williams TM. Comparative physiology of vocal musculature in two odontocetes, the bottlenose dolphin (Tursiops truncatus) and the harbor porpoise (Phocoena phocoena). J Comp Physiol B 2017; 188:177-193. [PMID: 28569355 DOI: 10.1007/s00360-017-1106-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 05/11/2017] [Indexed: 10/19/2022]
Abstract
The mechanism by which odontocetes produce sound is unique among mammals. To gain insight into the physiological properties that support sound production in toothed whales, we examined myoglobin content ([Mb]), non-bicarbonate buffering capacity (β), fiber-type profiles, and myosin heavy chain expression of vocal musculature in two odontocetes: the bottlenose dolphin (Tursiops truncatus; n = 4) and the harbor porpoise (Phocoena phocoena; n = 5). Both species use the same anatomical structures to produce sound, but differ markedly in their vocal repertoires. Tursiops produce both broadband clicks and tonal whistles, while Phocoena only produce higher frequency clicks. Specific muscles examined in this study included: (1) the nasal musculature around the phonic lips on the right (RNM) and left (LNM) sides of the head, (2) the palatopharyngeal sphincter (PPS), which surrounds the larynx and aids in pressurizing cranial air spaces, and (3) the genioglossus complex (GGC), a group of muscles positioned ventrally within the head. Overall, vocal muscles had significantly lower [Mb] and β than locomotor muscles from the same species. The PPS was predominately composed of small diameter slow-twitch fibers. Fiber-type and myosin heavy chain analyses revealed that the GGC was comprised largely of fast-twitch fibers (Tursiops: 88.6%, Phocoena: 79.7%) and had the highest β of all vocal muscles. Notably, there was a significant difference in [Mb] between the RNM and LNM in Tursiops, but not Phocoena. Our results reveal shared physiological characteristics of individual vocal muscles across species that enhance our understanding of key functional roles, as well as species-specific differences which appear to reflect differences in vocal capacities.
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Affiliation(s)
- Nicole M Thometz
- Department of Biology, University of San Francisco, 2130 Fulton St, San Francisco, CA, 94117, USA. .,Department of Ecology and Evolutionary Biology, Long Marine Laboratory, University of California at Santa Cruz, 115 McAllister Way, Santa Cruz, CA, 95060, USA.
| | - Jennifer L Dearolf
- Biology Department, Hendrix College, 1600 Washington Ave., Conway, AR, 72032, USA
| | - Robin C Dunkin
- Department of Ecology and Evolutionary Biology, Long Marine Laboratory, University of California at Santa Cruz, 115 McAllister Way, Santa Cruz, CA, 95060, USA
| | - Dawn P Noren
- Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Boulevard East, Seattle, WA, 98112, USA
| | - Marla M Holt
- Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Boulevard East, Seattle, WA, 98112, USA
| | - Olivia C Sims
- Biology Department, Hendrix College, 1600 Washington Ave., Conway, AR, 72032, USA
| | - Brandon C Cathey
- Biology Department, Hendrix College, 1600 Washington Ave., Conway, AR, 72032, USA
| | - Terrie M Williams
- Department of Ecology and Evolutionary Biology, Long Marine Laboratory, University of California at Santa Cruz, 115 McAllister Way, Santa Cruz, CA, 95060, USA
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10
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Ladds MA, Slip DJ, Harcourt RG. Swimming metabolic rates vary by sex and development stage, but not by species, in three species of Australian otariid seals. J Comp Physiol B 2016; 187:503-516. [PMID: 27803974 DOI: 10.1007/s00360-016-1046-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 10/12/2016] [Accepted: 10/20/2016] [Indexed: 11/28/2022]
Abstract
Physiology may limit the ability for marine mammals to adapt to changing environments. Depth and duration of foraging dives are a function of total available oxygen stores, which theoretically increase as animals grow, and metabolic costs. To evaluate how physiology may influence the travelling costs for seals to foraging patches in the wild, we measured metabolic rates of a cross-section of New Zealand fur seals, Australian fur seals and Australian sea lions representing different foraging strategies, development stages, sexes and sizes. We report values for standard metabolic rate, active metabolic rate (obtained from submerged swimming), along with estimates of cost of transport (COT), measured via respirometry. We found a decline in mass-specific metabolic rate with increased duration of submerged swimming. For most seals mass-specific metabolic rate increased with speed and for all seals mass-specific COT decreased with speed. Mass-specific metabolic rate was higher for subadult than adult fur seals and sea lions, corresponding to an overall higher minimum COT. Some sex differences were also apparent, such that female Australian fur seals and Australian sea lions had higher mass-specific metabolic rates than males. There were no species differences in standard or active metabolic rates for adult males or females. The seals in our study appear to operate at their physiological optimum during submerged swimming. However, the higher metabolic rates of young and female fur seals and sea lions may limit their scope for increasing foraging effort during times of resource limitation.
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Affiliation(s)
- Monique A Ladds
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia.
| | - David J Slip
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia.,Taronga Conservation Society Australia, Bradley's Head Road, Mosman, NSW, 2088, Australia
| | - Robert G Harcourt
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia
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11
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Shero MR, Costa DP, Burns JM. Scaling matters: incorporating body composition into Weddell seal seasonal oxygen store comparisons reveals maintenance of aerobic capacities. J Comp Physiol B 2015; 185:811-24. [PMID: 26164426 DOI: 10.1007/s00360-015-0922-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 06/24/2015] [Accepted: 07/02/2015] [Indexed: 12/24/2022]
Abstract
Adult Weddell seals (Leptonychotes weddellii) haul-out on the ice in October/November (austral spring) for the breeding season and reduce foraging activities for ~4 months until their molt in the austral fall (January/February). After these periods, animals are at their leanest and resume actively foraging for the austral winter. In mammals, decreased exercise and hypoxia exposure typically lead to decreased production of O2-carrying proteins and muscle wasting, while endurance training increases aerobic potential. To test whether similar effects were present in marine mammals, this study compared the physiology of 53 post-molt female Weddell seals in the austral fall to 47 pre-breeding females during the spring in McMurdo Sound, Antarctica. Once body mass and condition (lipid) were controlled for, there were no seasonal changes in total body oxygen (TBO2) stores. Within each season, hematocrit and hemoglobin values were negatively correlated with animal size, and larger animals had lower mass-specific TBO2 stores. But because larger seals had lower mass-specific metabolic rates, their calculated aerobic dive limit was similar to smaller seals. Indicators of muscular efficiency, myosin heavy chain composition, myoglobin concentrations, and aerobic enzyme activities (citrate synthase and β-hydroxyacyl CoA dehydrogenase) were likewise maintained across the year. The preservation of aerobic capacity is likely critical to foraging capabilities, so that following the molt Weddell seals can rapidly regain body mass at the start of winter foraging. In contrast, muscle lactate dehydrogenase activity, a marker of anaerobic metabolism, exhibited seasonal plasticity in this diving top predator and was lowest after the summer period of reduced activity.
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Affiliation(s)
- Michelle R Shero
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK, 99508, USA. .,School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA.
| | - Daniel P Costa
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Jennifer M Burns
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK, 99508, USA
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Moore CD, Fahlman A, Crocker DE, Robbins KA, Trumble SJ. The degradation of proteins in pinniped skeletal muscle: viability of post-mortem tissue in physiological research. CONSERVATION PHYSIOLOGY 2015; 3:cov019. [PMID: 27293704 PMCID: PMC4778441 DOI: 10.1093/conphys/cov019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 03/21/2015] [Accepted: 04/11/2015] [Indexed: 06/06/2023]
Abstract
As marine divers, pinnipeds have a high capacity for exercise at depth while holding their breath. With finite access to oxygen, these species need to be capable of extended aerobic exercise and conservation of energy. Pinnipeds must deal with common physiological hurdles, such as hypoxia, exhaustion and acidosis, that are common to all exercising mammals. The physiological mechanisms in marine mammals used for managing oxygen and carbon dioxide have sparked much research, but access to animals and tissues is difficult and requires permits. Deceased animals that are either bycaught or stranded provide one potential source for tissues, but the validity of biochemical data from post-mortem samples has not been rigorously assessed. Tissues collected from stranded diving mammals may be a crucial source to add to our limited knowledge on the physiology of some of these animals and important to the conservation and management of these species. We aim to determine the reliability of biochemical assays derived from post-mortem tissue and to promote the immediate sampling of stranded animals for the purpose of physiological research. In this study, we mapped the temporal degradation of muscle enzymes from biopsied Northern elephant seals (Mirounga angustirostris) and highlight recommendations for storage protocols for the best preservation of tissue. We also compared the enzymatic activity of different muscle groups (pectoral and latissimus dorsi) in relation to locomotion and measured the effects of four freeze-thaw cycles on muscle tissue enzyme function. Results indicate that enzymatic activity fluctuates greatly, especially with varying storage temperature, storage time, species and muscle group being assayed. In contrast, proteins, such as myoglobin, remain relatively continuous in their increase at 4°C for 48 h. Stranded animals can be a valuable source of biochemical data, but enzyme assays should be used only with great caution in post-mortem tissues.
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Affiliation(s)
- Colby D. Moore
- Department of Biology, Baylor University, One Bear Place, Waco, TX 76706, USA
| | - Andreas Fahlman
- Department of Life Sciences, Texas A&M University Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412, USA
| | - Daniel E. Crocker
- Department of Biology, Sonoma State University, 1801 East Cotati Avenue, Rohnert Park, CA 94928, USA
| | - Kathleen A. Robbins
- Department of Biology, Baylor University, One Bear Place, Waco, TX 76706, USA
| | - Stephen J. Trumble
- Department of Biology, Baylor University, One Bear Place, Waco, TX 76706, USA
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Thometz NM, Murray MJ, Williams TM. Ontogeny of Oxygen Storage Capacity and Diving Ability in the Southern Sea Otter (Enhydra lutris nereis): Costs and Benefits of Large Lungs. Physiol Biochem Zool 2015; 88:311-27. [DOI: 10.1086/681019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Burns JM, Lestyk K, Freistroffer D, Hammill MO. Preparing Muscles for Diving: Age-Related Changes in Muscle Metabolic Profiles in Harp (Pagophilus groenlandicus) and Hooded (Cystophora cristata) Seals. Physiol Biochem Zool 2015; 88:167-82. [PMID: 25730272 DOI: 10.1086/680015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
In adult marine mammals, muscles can sustain aerobic metabolism during dives in part because they contain large oxygen (O2) stores and metabolic rates are low. However, young pups have significantly lower tissue O2 stores and much higher mass-specific metabolic rates. To investigate how these differences may influence muscle function during dives, we measured the activities of enzymes involved in aerobic and anaerobic metabolic pathways (citrate synthase [CS], β-hydroxyacyl-coenzyme A dehydrogenase [HOAD], lactate dehydrogenase [LDH]) and the LDH isoform profile in six muscles from 41 harp (Pagophilus groenlandicus) and 30 hooded (Cystophora cristata) seals ranging in age from fetal to adult. All neonatal muscles had significantly higher absolute but lower metabolically scaled CS and HOAD activities than adults (∼ 70% and ∼ 85% lower, respectively). Developmental increases in LDH activity lagged that of aerobic enzymes and were not accompanied by changes in isozyme profile, suggesting that changes in enzyme concentration rather than structure determine activity levels. Biochemical maturation proceeded faster in the major locomotory muscles. In combination, findings suggest that pup muscles are unable to support strenuous aerobic exercise or rely heavily on anaerobic metabolism during early diving activities and that pups' high mass-specific metabolic rates may play a key role in limiting the ability of their muscles to support underwater foraging.
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Affiliation(s)
- J M Burns
- Department of Biological Sciences, University of Alaska, Anchorage, Alaska 99508; 2Department of Life Sciences, Great Basin College, Elko, Nevada 89801; 3Maurice Lamontagne Institute, Department of Fisheries and Oceans, Mont-Joli, Québec, Canada
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Rosen DAS, Volpov BL, Trites AW. Short-term episodes of imposed fasting have a greater effect on young northern fur seals (Callorhinus ursinus) in summer than in winter. CONSERVATION PHYSIOLOGY 2014; 2:cou021. [PMID: 27293642 PMCID: PMC4732476 DOI: 10.1093/conphys/cou021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 05/05/2014] [Accepted: 05/08/2014] [Indexed: 05/11/2023]
Abstract
An unexpected shortage of food may affect wildlife in a different way depending on the time of year when it occurs. We imposed 48 h fasts on six female northern fur seals (Callorhinus ursinus; ages 6-24 months) to identify times of year when they might be particularly sensitive to interruptions in food supply. We monitored changes in their resting metabolic rates and their metabolic response to thermal challenges, and also examined potential bioenergetic causes for seasonal differences in body mass loss. The pre-fast metabolism of the fur seals while in ambient air or submerged in water at 4°C was higher during summer (June to Sepember) than winter (November to March), and submergence did not significantly increase metabolism, indicating a lack of additional thermoregulatory costs. There was no evidence of metabolic depression following the fasting periods, nor did metabolism increase during the post-fast thermal challenge, suggesting that mass loss did not negatively impact thermoregulatory capacity. However, the fur seals lost mass at greater rates while fasting during the summer months, when metabolism is normally high to facilitate faster growth rates (which would ordinarily have been supported by higher food intake levels). Our findings suggest that summer is a more critical time of year than winter for young northern fur seals to obtain adequate nutrition.
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Affiliation(s)
- David A. S. Rosen
- Marine Mammal Research Unit, Fisheries Centre, University of British Columbia, AERL 247, 2202 Main Mall, Vancouver, BC, Canada V6T 1Z4
- Corresponding author: Marine Mammal Research Unit, Fisheries Centre, University of British Columbia, AERL 247, 2202 Main Mall, Vancouver, BC, Canada V6T 1Z4. Tel: +1 604 822 8184.
| | - Beth L. Volpov
- School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia
| | - Andrew W. Trites
- Marine Mammal Research Unit, Fisheries Centre, University of British Columbia, AERL 247, 2202 Main Mall, Vancouver, BC, Canada V6T 1Z4
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A review of the multi-level adaptations for maximizing aerobic dive duration in marine mammals: from biochemistry to behavior. J Comp Physiol B 2013; 184:23-53. [DOI: 10.1007/s00360-013-0782-z] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 08/27/2013] [Accepted: 08/30/2013] [Indexed: 11/26/2022]
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Horning M. Constraint lines and performance envelopes in behavioral physiology: the case of the aerobic dive limit. Front Physiol 2012; 3:381. [PMID: 23055984 PMCID: PMC3458304 DOI: 10.3389/fphys.2012.00381] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2012] [Accepted: 09/08/2012] [Indexed: 11/18/2022] Open
Abstract
Constraint lines-the boundaries that delimit point clouds in bivariate scattergrams-have been applied in macro-ecology to quantify the effects of limiting factors on response variables, but have not been applied to the behavioral performance and physiological ecology of individual vertebrates. I propose that behavioral scattergrams of air-breathing, diving vertebrates contain informative edges that convey insights into physiological constraints that shape the performance envelopes of divers. In the classic example of repeated cycles of apnea and eupnea in diving, air-breathing vertebrates, the need to balance oxygen consumption, and intake should differentially constrain recovery for dives within or exceeding the aerobic dive limit (ADL). However, the bulk of variance observed in recovery versus dive duration scattergrams originates from undetermined behavioral variables, and deviations from overall stasis may become increasingly apparent at progressively smaller scales of observation. As shown on dive records from 79 Galápagos fur seals, the selection of appropriate time scales of integration yields two distinct recovery boundaries for dive series within and beyond the estimated ADL. An analysis of the corresponding constraint lines is independent of central tendencies in data and avoids violating parametric assumptions for large data sets where variables of interest account for only a small portion of observed variance. I hypothesize that the intercept between these constraint lines represents the effective ADL, and present physiological and ecological considerations to support this hypothesis.
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Affiliation(s)
- Markus Horning
- Department of Fisheries and Wildlife, Marine Mammal Institute, Oregon State UniversityNewport, OR, USA
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LaRosa DA, Cannata DJ, Arnould JPY, O'Sullivan LA, Snow RJ, West JM. Changes in muscle composition during the development of diving ability in the Australian fur seal. AUST J ZOOL 2012. [DOI: 10.1071/zo11072] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
During development the Australian fur seal transitions from a terrestrial, maternally dependent pup to an adult marine predator. Adult seals have adaptations that allow them to voluntarily dive at depth for long periods, including increased bradycardic control, increased myoglobin levels and haematocrit. To establish whether the profile of skeletal muscle also changes in line with the development of diving ability, biopsy samples were collected from the trapezius muscle of pups, juveniles and adults. The proportions of different fibre types and their oxidative capacity were determined. Only oxidative fibre types (Type I and IIa) were identified, with a significant change in proportions from pup to adult. There was no change in oxidative capacity of Type I and IIa fibres between pups and juveniles but there was a two-fold increase between juveniles and adults. Myoglobin expression increased between pups and juveniles, suggesting improved oxygen delivery, but with no increase in oxidative capacity, oxygen utilisation within the muscle may still be limited. Adult muscle had the highest oxidative capacity, suggesting that fibres are able to effectively utilise available oxygen during prolonged dives. Elevated levels of total creatine in the muscles of juveniles may act as an energy buffer when fibres are transitioning from a fast to slow fibre type.
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