More Like this

1. Diving physiology of marine mammals and birds: the development of biologging techniques

   https://doi.org/10.1098/rstb.2020.0211  

   Williams, Cassondra L.; Ponganis, Paul J. (August 2021, Philosophical Transactions of the Royal Society B: Biological Sciences)

   null (Ed.)

   In the 1940s, Scholander and Irving revealed fundamental physiological responses to forced diving of marine mammals and birds, setting the stage for the study of diving physiology. Since then, diving physiology research has moved from the laboratory to the field. Modern biologging, with the development of microprocessor technology, recorder memory capacity and battery life, has advanced and expanded investigations of the diving physiology of marine mammals and birds. This review describes a brief history of the start of field diving physiology investigations, including the invention of the time depth recorder, and then tracks the use of biologging studies in four key diving physiology topics: heart rate, blood flow, body temperature and oxygen store management. Investigations of diving heart rates in cetaceans and O 2 store management in diving emperor penguins are highlighted to emphasize the value of diving physiology biologging research. The review concludes with current challenges, remaining diving physiology questions and what technologies are needed to advance the field. This article is part of the theme issue ‘Measuring physiology in free-living animals (Part I)’. 

   more » « less
2. Field physiology in the aquatic realm: ecological energetics and diving behavior provide context for elucidating patterns and deviations

   https://doi.org/10.1242/jeb.245832  

   Costa, Daniel P; Favilla, Arina B (October 2023, Journal of Experimental Biology)

   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. 

   more » « less
3. Advances in thermal physiology of diving marine mammals: The dual role of peripheral perfusion

   https://doi.org/10.1080/23328940.2021.1988817  

   Favilla, Arina B.; Horning, Markus; Costa, Daniel P. (October 2021, Temperature)

   null (Ed.)

   The ability to maintain a high core body temperature is a defining characteristic of all mammals, yet their diverse habitats present disparate thermal challenges that have led to specialized adaptations. Marine mammals inhabit a highly conductive environment. Their thermoregulatory capabilities far exceed our own despite having limited avenues of heat transfer. Additionally, marine mammals must balance their thermoregulatory demands with those associated with diving (i.e. oxygen conservation), both of which rely on cardiovascular adjustments. This review presents the progress and novel efforts in investigating marine mammal thermoregulation, with a particular focus on the role of peripheral perfusion. Early studies in marine mammal thermal physiology were primarily performed in the laboratory and provided foundational knowledge through in vivo experiments and ex vivo measurements. However, the ecological relevance of these findings remains unknown because comparable efforts on free-ranging animals have been limited. We demonstrate the utility of biologgers for studying their thermal adaptations in the context in which they evolved. Our preliminary results from freely diving northern elephant seals (Mirounga angustirostris) reveal blubber’s dynamic nature and the complex interaction between thermoregulation and the dive response due to the dual role of peripheral perfusion. Further exploring the potential use of biologgers for measuring physiological variables relevant to thermal physiology in other marine mammal species will enhance our understanding of the relative importance of morphology, physiology, and behavior for thermoregulation and overall homeostasis. 

   more » « less
4. Contrasting offspring dependence periods and diving development rates in two closely related marine mammal species

   https://doi.org/10.1098/rsos.230666  

   Jouma'a, Joffrey; Orgeret, Florian; Picard, Baptiste; Robinson, Patrick W; Weimerskirch, Henri; Guinet, Christophe; Costa, Daniel P; Beltran, Roxanne S (January 2024, Royal Society Open Science)

   Understanding the ontogeny of diving behaviour in marine megafauna is crucial owing to its influence on foraging success, energy budgets, and mortality. We compared the ontogeny of diving behaviour in two closely related species—northern elephant seals (Mirounga angustirostris, n= 4) and southern elephant seals (Mirounga leonina, n= 9)—to shed light on the ecological processes underlying migration. Although both species have similar sizes and behaviours as adults, we discovered that juvenile northern elephant seals have superior diving development, reaching 260 m diving depth in just 30 days, while southern elephant seals require 160 days. Similarly, northern elephant seals achieve dive durations of approximately 11 min on their first day of migration, while southern elephant seals take 125 days. The faster physiological maturation of northern elephant seals could be related to longer offspring dependency and post-weaning fast durations, allowing them to develop their endogenous oxygen stores. Comparison across both species suggests that weaned seal pups face a trade-off between leaving early with higher energy stores but poorer physiological abilities or leaving later with improved physiology but reduced fat stores. This trade-off might be influenced by their evolutionary history, which shapes their migration behaviours in changing environments over time. 

   more » « less
5. Fetal growth, high altitude, and evolutionary adaptation: a new perspective

   https://doi.org/10.1152/ajpregu.00067.2021  

   Wilsterman, Kathryn; Cheviron, Zachary A. (September 2021, American Journal of Physiology-Regulatory, Integrative and Comparative Physiology)

   null (Ed.)

   Residence at high altitude is consistently associated with low birthweight among placental mammals. This reduction in birthweight influences long-term health trajectories for both the offspring and mother. However, the physiological processes that contribute to fetal growth restriction at altitude are still poorly understood, and thus our ability to safely intervene remains limited. One approach to identify the factors that mitigate altitude-dependent fetal growth restriction is to study populations that are protected from fetal growth restriction through evolutionary adaptations (e.g., high altitude-adapted populations). Here, we examine human gestational physiology at high altitude from a novel evolutionary perspective that focuses on patterns of physiological plasticity, allowing us to identify 1) the contribution of specific physiological systems to fetal growth restriction and 2) the mechanisms that confer protection in highland-adapted populations. Using this perspective, our review highlights two general findings: first, that the beneficial value of plasticity in maternal physiology is often dependent on factors more proximate to the fetus; and second, that our ability to understand the contributions of these proximate factors is currently limited by thin data from altitude-adapted populations. Expanding the comparative scope of studies on gestational physiology at high altitude and integrating studies of both maternal and fetal physiology are needed to clarify the mechanisms by which physiological responses to altitude contribute to fetal growth outcomes. The relevance of these questions to clinical, agricultural, and basic research combined with the breadth of the unknown highlight gestational physiology at high altitude as an exciting niche for continued work. 

   more » « less