UA01-Teses
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Browsing UA01-Teses by advisor "Abecasis, David Maria Aguiar"
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- Thermoregulation strategies of the ocean's widest ranging ectothermic shark, Prionace glauca (Linnaeus, 1758)Publication . Mendes, Maria João Marques; Queiroz, Nuno; Abecasis, David Maria AguiarLarge pelagic predators have distinct physiologies (Block, 2005), extensive movements, and broad distributions, and they exert top-down control in open ocean ecosystems (Heithaus et al., 2008; Block et al., 2011), shaping the ecological structure and habitat use of communities and providing an indication of ocean state (Sims and Quayle, 1998; Sims, 2003; Campana, 2016; Boerder et al., 2019). Climate changes are expected to alter existing environments and generate new ones, potentially leading to local loss of organisms and their related ecosystem function (Corrales et al., 2018; Pinsky et al., 2019; Yeruham et al., 2020). Marine ecosystems are characterized by vertical gradients, defined by physical (e.g., temperature, light level, oxygen concentration) (Brill and Lutcavage, 2001) and biological properties (e.g., primary production). Temperature is one of the most significant abiotic factors influencing animals' distribution, behavior, and physiological performance, especially for ectotherms that cannot regulate their body temperature internally (Angilletta et al., 2002). Large marine ectotherms are generally adapted to live within a narrow temperature range, resulting in a thermal optimum that optimizes their physiological performance (Neill, 1979; Costa, 2018). We used archival tags to record the diving behavior, and muscle temperature of six blue sharks, Prionace glauca (Linnaeus, 1758). Consistent dive patterns were observed for all sharks, with a wide variation of depth (1.60 - 711.10 m). The thermal gradient of the water column was proportional to the depth. All individuals had a similar ambient temperature on average (between 17.06 ± 4.53 ºC and 20.06 ± 2.19 ºC). Although the muscle temperature showed slower and smoother fluctuations, was directly influenced by the ambient temperature). Their high thermal inertia allows blue sharks to make short foraging trips to deep cold waters without significantly reducing their body temperature, as they warm up again at shallow depths (Watanabe et al., 2019). In general, muscles presented a higher and stricter range of temperature. Blue sharks shift vertical swimming directions (descending or ascending) before their body temperature reaches the ambient water temperature, presenting a greater whole-body heat transfer coefficients during the warming (ascendent) phase. Thus, this thermoregulatory behavior linked to the search for food explains blue sharks' vertically and geographically broad thermal niches. Understanding how species' physiology, behavior, and ecology interact with environmental temperature is critical for predicting changes in their movement, distribution, and ecological function in response to climate change and improving conservation measures.