Physiology as Integrated Systems in The Biology of Sea Turtles
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Abstract
The discipline of integrative biology explores the structure and function of biological systems at multiple levels of organization. Within this field, physiologists investigate how living organisms function by studying processes at the molecular, cellular, and organismal levels. Data collected through controlled laboratory experiments and carefully designed field studies contribute to our understanding of physiological responses to variable and challenging environmental conditions, and provide insight into the limits of physiological performance. Modern, integrative studies of animal physiology have roots in the field of physiological ecology, a discipline that incorporates a comparative approach to investigate physiological and biochemical mechanisms and their adaptive significance. Increasingly, we recognize the need for integrating data on physiological attributes of individual organisms with population level effects, particularly for species with threatened or endangered status. Abiotic factors (e.g. temperature, humidity, salinity, and oxygen availability) and biotic factors (e.g. social interactions, prey availability and predation risk) have profound effects on physiological processes, which may in turn impact an individual’s ability to acquire resources from the environment and allocate acquired energy to activities critical to survival and fitness (Fig 1). An understanding of physiological functioning of individual organisms is, therefore, quite important for assessing the potential impacts of natural or anthropogenic environmental perturbations on a given population (Dunham et al. 1989, Carey 2005, Tracy et al. 2006, Wikelski and Cooke 2006, Chown and Gaston 2008). Sea turtles are highly migratory reptiles that inhabit the marine realm and spend the majority of their time submerged beneath the ocean surface. The metabolic adaptations and physiological mechanisms underlying their capacity for long-distance movements, prolonged dive durations, and maintenance of osmotic homeostasis have been the subject of intense interest for many years. Early investigations of sea turtle physiology were conducted in laboratory settings, and provided detailed information about physiological responses to submergence, salt-loading, and various temperature treatments under tightly controlled conditions. Over the past several decades, the development of sophisticated remote-monitoring technologies has permitted investigations of the physiology of sea turtles freely swimming at sea. Integration of behavioral and physiological data collected from both laboratory and field studies has yielded a clearer picture of how sea turtles are adapted for a marine existence and how they respond to alterations in their environment. This chapter will highlight aspects of sea turtle physiology central to their ability to exploit the marine environment. Our exploration of sea turtle physiology will begin with an overview of metabolism and energetics, as all physiological tasks performed by an animal depend on acquisition, processing, and allocation of chemical energy. Within the broad framework of metabolic physiology, we will consider the effects of temperature on biochemical and physiological processes and discuss mechanisms to manage oxygen stores while diving and maintain osmotic homeostasis. Aspects of physiological function at multiple levels of biological organization will be presented for each topic covered. The chapter will conclude with illustrations of the relevance of physiological studies to sea turtle conservation
