Arina b
A schematic comparing the variation in temperature experienced by air-breathing marine vertebrates while on land (A) and diving at-sea (B). Thus, recognizing the temporal and spatial range of thermal challenges faced by marine air-breathers is essential when considering the suitability of their thermal adaptations for maintaining homeostasis ( Figure 1).įigure 1. The exceptions are shallow divers that remain in the mixed layer or polar species that are exposed to cold temperatures throughout the water column. While this large shift in their thermal environment occurs over weeks to months, marine vertebrates also experience significant temperature changes on the timescale of seconds to minutes while diving. Additionally, some migrate long distances from tropical breeding to polar foraging grounds where sea surface temperatures can vary from 30☌ to −2☌ ( Corkeron and Connor, 1999 Guerrero and Rogers, 2019). Some species, like the Galápagos fur seal, Arctocephalus galapagoensis, experience an extreme dichotomy in their thermal environments that requires different thermoregulatory strategies: dissipating excess heat while breeding on land in warm climates and conserving heat while foraging in cold waters ( Costa and Maresh, 2017 Chilvers, 2018).
#Arina b full#
While some have made the full transition to an aquatic lifestyle, others are tied to the land for reproduction and molting ( Costa, 1991 Davenport, 1997 Schreiber and Burger, 2002), which exposes them to the contrasting thermal demands imposed by air and water. In addition to spanning the endothermy-ectothermy spectrum, marine air-breathing vertebrates have different lifestyles that expose them to a wide range of thermal environments. Multiple independent transitions from a terrestrial to marine life were made possible by developing a concomitant, often converging, suite of morphological, physiological, and behavioral adaptations that allow marine vertebrates to meet their thermoregulatory needs ( Reidenberg, 2007 Pyenson et al., 2014 Kelley and Pyenson, 2015). Thus, the avenues of heat exchange that animals can use to control their thermal balance are more limited in water. Moreover, the implications for aquatic vertebrate thermal physiology are significant as heat transfers about 25 times faster in water than in air. While they all share the same aquatic environment and its associated challenges, air-breathers are faced with an additional challenge: the spatial separation of two critical resources, air and food ( Whittow, 1987 Boyd, 1997 Rosen et al., 2007). Marine vertebrates can be categorized as either “air-breathers” or “water-breathers”. Expanding the use of physiological biologgers, particularly to understudied species, will enhance our understanding of how these animals coordinate various physiological demands to maintain homeostasis in a thermally challenging environment. We hope that a review and synthesis of both laboratory and field studies will stimulate future research efforts at the intersection of thermoregulation and diving physiology. Studies have demonstrated that thermoregulatory strategies can involve the temporal separation of two conflicting responses, a compromise in the performance of one response over another, or coordination of synergistic responses. We reviewed the literature on thermoregulation while diving in an effort to synthesize our current understanding of the thermoregulatory strategies of diving air-breathing marine vertebrates. The adjustments required to meet one physiological demand may not be compatible with another and can result in a potential conflict between the various physiological demands imposed on air-breathing divers. The cardiovascular system is integral to the physiological responses associated with the dive response, exercise, digestion, and thermoregulation. However, the physiological and behavioral mechanisms used to maintain thermal balance while diving is still poorly understood. In response to these challenges, air-breathing vertebrates have developed morphological and physiological adaptations that align with their life histories and phylogenies and contribute to homeostasis. In addition to temperature changes across their range, air-breathing vertebrates experience temperature changes on the timescale of seconds to minutes as they perform dives to access two critical resources: air at the surface and food at depth. The aquatic habitat of marine “air-breathing” vertebrates provides a significant thermoregulatory challenge due to the high thermal conductivity of water. Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, United States.