Matching Items (4)
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- All Subjects: Physiology
- Creators: DeNardo, Dale F
Description
As water is essential for survival, seasonal scarcity of freshwater resources can pose a challenge for many species. In xeric environments, efficient location of ephemeral water is crucial to capitalize on this rare, critical resource. Yet little is known about how organisms locate water, though it has been acknowledged that olfactory spatial navigation may benefit water searching in xeric-adapted species. Additionally, drinking behavior may be influenced by water salinity as consuming water with salinity levels that exceed blood osmolality can induce or exacerbate dehydration. To investigate whether animals can locate water via olfaction, whether salinity affects the amount of water consumed, and whether the extent of dehydration affects both processes, I conducted three experiments in a xeric-adapted reptile, the Gila monster (Heloderma suspectum). Two experiments used a T-maze to examine the effects of various olfactory cues and hydration state on spatial navigation to water resources, while the third experiment examined willingness to drink water of various salinity levels depending on the extent of dehydration. I found that Gila monsters accurately navigated to olfactory cues associated with aged tap water, but not other olfactory cues (pond water, geosmin/MIB, IBMP/IPMP). Increased extent of dehydration correlated with greater spatial navigation efficiency but did not meaningfully impact navigation accuracy. Moderately dehydrated Gila monsters selectively consumed water with lower salinity levels (freshwater, 1,250 ppm, and 2,500 ppm) and avoided highly saline water resources (10,000 ppm and 20,000 ppm). However, considerably dehydrated animals demonstrated an increased propensity to consume water with higher salinity levels. These results provide evidence for olfactory spatial navigation and selective consumption of saline water as strategies to locate water and efficiently osmoregulate in an osmotically challenging environment. These findings underscore the observed adaptable physiological and behavioral traits Gila monsters and other xeric-adapted species use to endure the seasonal water limitations.
ContributorsNorthrop, Victoria (Author) / DeNardo, Dale F (Thesis advisor) / Gerber, Leah R (Committee member) / Martins, Emilia P (Committee member) / Arizona State University (Publisher)
Created2024
Description
Environmental variation impacts physiological performance in animals. As a result, many animals thermoregulate to buffer unfavorable thermal variation in their environments. Animals are only expected to thermoregulate when the benefits outweigh the costs, although both are difficult to quantify. I examined how habitats and organismal factors shape thermoregulation and physiological performance in lizards. I found that habitat structure shapes opportunities for thermoregulation in two species of Anolis lizards. In dense tropical rainforests where there is low habitat heterogeneity, the range of available microclimates is narrow. Consequently, lizards in the tropics tend to be thermal specialists – performing best over a narrow range of temperatures. This phenotype should lead to decreased performance under climate warming. I then investigated the relationship between body condition, feeding, and thermoregulation in Yarrow’s spiny lizards (Sceloporus jarrovii) using lab- and field-based experiments. In the lab experiment, when lizards were observed in an artificial thermal gradient, neither body condition nor feeding status influenced the mean body temperature. When simulated costs of thermoregulation were higher, all lizards reduced thermoregulation similarly. However, when lizards were observed in an outdoor thermal arena, individuals with lower body condition decreased thermoregulatory performance, resulting in a lower mean body temperature. Animals with poor body condition may face greater risk of predation when thermoregulating. Finally, I conducted a comparative analysis to quantify relationships between the potential for thermoregulatory performance and empirical measures of productivity (i.e., growth rates and reproductive output) in lizard populations. A model that assumes lizards are active whenever preferred temperatures were available overestimated the duration that a lizard could maintain a preferred body temperature. As such, studies equating predicted thermoregulatory performance with fitness in the context of climate change should be interpreted cautiously. Overall, environmental factors and organismal traits shape the thermoregulatory behavior of animals, ultimately affecting their physiological performance and fitness. Biologists should consider these relationships when modeling the impacts of climate change on future performance.
ContributorsNeel, Lauren (Author) / Angilletta, Michael J (Thesis advisor) / Bateman, Heather L (Committee member) / DeNardo, Dale F (Committee member) / Sears, Michael W (Committee member) / Arizona State University (Publisher)
Created2023
Description
Environmental changes are occurring at an unprecedented rate, and these changes will undoubtedly lead to alterations in resource availability for many organisms. To effectively predict the implications of such changes, it is critical to better understand how organisms have adapted to coping with seasonally limited resources. The vast majority of previous work has focused on energy balance as the driver of changes in organismal physiology. While energy is clearly a vital currency, other resources can also be limited and impact physiological functions. Water is essential for life as it is the main constituent of cells, tissues, and organs. Yet, water has received little consideration for its role as a currency that impacts physiological functions. Given the importance of water to most major physiological systems, I investigated how water limitations interact with immune function, metabolism, and reproductive investment, an almost entirely unexplored area. Using multiple species and life stages, I demonstrated that dehydrated animals typically have enhanced innate immunity, regardless of whether the dehydration is a result of seasonal water constraints, water deprivation in the lab, or high physiological demand for water. My work contributed greatly to the understanding of immune function dynamics and lays a foundation for the study of hydration immunology as a component of the burgeoning field of ecoimmunology. While a large portion of my dissertation focused on the interaction between water balance and immune function, there are many other physiological processes that may be impacted by water restrictions. Accordingly, I recently expanded the understanding of how reproductive females can alter metabolic substrates to reallocate internal water during times of water scarcity, an important development in our knowledge of reproductive investments. Overall, by thoroughly evaluating implications and responses to water limitations, my dissertation, when combined previous acquired knowledge on food limitation, will enable scientists to better predict the impacts of future climate change, where, in many regions, rainfall events are forecasted to be less reliable, resulting in more frequent drought.
ContributorsBrusch, George, IV (Author) / DeNardo, Dale F (Thesis advisor) / Blattman, Joseph (Committee member) / French, Susannah (Committee member) / Sabo, John (Committee member) / Taylor, Emily (Committee member) / Arizona State University (Publisher)
Created2019
Description
Agassiz’s desert tortoise (Gopherus agassizii) is a long-lived species native to the Mojave Desert and is listed as threatened under the US Endangered Species Act. To aid conservation efforts for preserving the genetic diversity of this species, we generated a whole genome reference sequence with an annotation based on deep transcriptome sequences of adult skeletal muscle, lung, brain, and blood. The draft genome assembly for G. agassizii has a scaffold N50 length of 252 kbp and a total length of 2.4 Gbp. Genome annotation reveals 20,172 protein-coding genes in the G. agassizii assembly, and that gene structure is more similar to chicken than other turtles. We provide a series of comparative analyses demonstrating (1) that turtles are among the slowest-evolving genome-enabled reptiles, (2) amino acid changes in genes controlling desert tortoise traits such as shell development, longevity and osmoregulation, and (3) fixed variants across the Gopherus species complex in genes related to desert adaptations, including circadian rhythm and innate immune response. This G. agassizii genome reference and annotation is the first such resource for any tortoise, and will serve as a foundation for future analysis of the genetic basis of adaptations to the desert environment, allow for investigation into genomic factors affecting tortoise health, disease and longevity, and serve as a valuable resource for additional studies in this species complex.
Data Availability: All genomic and transcriptomic sequence files are available from the NIH-NCBI BioProject database (accession numbers PRJNA352725, PRJNA352726, and PRJNA281763). All genome assembly, transcriptome assembly, predicted protein, transcript, genome annotation, repeatmasker, phylogenetic trees, .vcf and GO enrichment files are available on Harvard Dataverse (doi:10.7910/DVN/EH2S9K).
ContributorsTollis, Marc (Author) / DeNardo, Dale F (Author) / Cornelius, John A (Author) / Dolby, Greer A (Author) / Edwards, Taylor (Author) / Henen, Brian T. (Author) / Karl, Alice E. (Author) / Murphy, Robert W. (Author) / Kusumi, Kenro (Author)
Created2017-05-31