Matching Items (10)
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- All Subjects: Physiology
- All Subjects: Reptiles
- All Subjects: conservation
- Creators: DeNardo, Dale
- Member of: Theses and Dissertations
Description
Conditions during development can shape the expression of traits at adulthood, a phenomenon called developmental plasticity. In this context, factors such as nutrition or health state during development can affect current and subsequent physiology, body size, brain structure, ornamentation, and behavior. However, many of the links between developmental and adult phenotype are poorly understood. I performed a series of experiments using a common molecular currency - carotenoid pigments - to track somatic and reproductive investments through development and into adulthood. Carotenoids are red, orange, or yellow pigments that: (a) animals must acquire from their diets, (b) can be physiologically beneficial, acting as antioxidants or immunostimulants, and (c) color the sexually attractive features (e.g., feathers, scales) of many animals. I studied how carotenoid nutrition and immune challenges during ontogeny impacted ornamental coloration and immune function of adult male mallard ducks (Anas platyrhynchos). Male mallards use carotenoids to pigment their yellow beak, and males with more beaks that are more yellow are preferred as mates, have increased immune function, and have higher quality sperm. In my dissertation work, I established a natural context for the role that carotenoids and body condition play in the formation of the adult phenotype and examined how early-life experiences, including immune challenges and dietary access to carotenoids, affect adult immune function and ornamental coloration. Evidence from mallard ducklings in the field showed that variation in circulating carotenoid levels at hatch are likely driven by maternal allocation of carotenoids, but that carotenoid physiology shifts during the subsequent few weeks to reflect individual foraging habits. In the lab, adult beak color expression and immune function were more tightly correlated with body condition during growth than body condition during subsequent stages of development or adulthood. Immune challenges during development affected adult immune function and interacted with carotenoid physiology during adulthood, but did not affect adult beak coloration. Dietary access to carotenoids during development, but not adulthood, also affected adult immune function. Taken together, these results highlight the importance of the developmental stage in shaping certain survival-related traits (i.e., immune function), and lead to further questions regarding the development of ornamental traits.
ContributorsButler, Michael (Author) / McGraw, Kevin J. (Thesis advisor) / Chang, Yung (Committee member) / Deviche, Pierre (Committee member) / DeNardo, Dale (Committee member) / Rutowski, Ronald (Committee member) / Arizona State University (Publisher)
Created2012
Description
Land management practices such as domestic animal grazing can alter plant communities via changes in soil structure and chemistry, species composition, and plant nutrient content. These changes can affect the abundance and quality of plants consumed by insect herbivores with consequent changes in population dynamics. These population changes can translate to massive crop damage and pest control costs. My dissertation focused on Oedaleus asiaticus, a dominant Asian locust, and had three main objectives. First, I identified morphological, physiological, and behavioral characteristics of the migratory ("brown") and non-migratory ("green") phenotypes. I found that brown morphs had longer wings, larger thoraxes and higher metabolic rates compared to green morphs, suggesting that developmental plasticity allows greater migratory capacity in the brown morph of this locust. Second, I tested the hypothesis of a causal link between livestock overgrazing and an increase in migratory swarms of O. asiaticus. Current paradigms generally assume that increased plant nitrogen (N) should enhance herbivore performance by relieving protein-limitation, increasing herbivorous insect populations. I showed, in contrast to this scenario, that host plant N-enrichment and high protein artificial diets decreased the size and viability of O. asiaticus. Plant N content was lowest and locust abundance highest in heavily livestock-grazed fields where soils were N-depleted, likely due to enhanced erosion and leaching. These results suggest that heavy livestock grazing promotes outbreaks of this locust by reducing plant protein content. Third, I tested for the influence of dietary imbalance, in conjunction with high population density, on migratory plasticity. While high population density has clearly been shown to induce the migratory morph in several locusts, the effect of diet has been unclear. I found that locusts reared at high population density and fed unfertilized plants (i.e. high quality plants for O. asiaticus) had the greatest migratory capacity, and maintained a high percent of brown locusts. These results did not support the hypothesis that poor-quality resources increased expression of migratory phenotypes. This highlights a need to develop new theoretical frameworks for predicting how environmental factors will regulate migratory plasticity in locusts and perhaps other insects.
ContributorsCease, Arianne (Author) / Harrison, Jon (Thesis advisor) / Elser, James (Thesis advisor) / DeNardo, Dale (Committee member) / Quinlan, Michael (Committee member) / Sabo, John (Committee member) / Arizona State University (Publisher)
Created2012
Description
Parental care provides many benefits to offspring. One widely realized benefit is enhanced regulation of offspring's thermal environment. The developmental thermal environment during development can be optimized behaviorally through nest site selection and brooding, and it can be further enhanced by physiological heat production. In fact, enhancement of the developmental thermal environment has been proposed as the initial driving force for the evolution of endothermy in bird and mammals. I used pythons (Squamata: Pythonidae) to expand existing knowledge of behavioral and physiological parental tactics used to regulate offspring thermal environment. I first demonstrated that brooding behavior in the Children's python (Antaresia childreni) is largely driven by internal mechanisms, similar to solitary birds, suggesting that the early evolution of the parent-offspring association was probably hormonally driven. Two species of python are known to be facultatively thermogenic (i.e., are endothermic during reproduction). I expand current knowledge of thermogenesis in Burmese pythons (Python molurus) by demonstrating that females use their own body temperature to modulate thermogenesis. Although pythons are commonly cited as thermogenic, the actual extent of thermogenesis within the family Pythonidae is unknown. Thus, I assessed the thermogenic capability of five previously unstudied species of python to aid in understanding phylogenetic, morphological, and distributional influences on thermogenesis in pythons. Results suggest that facultative thermogenesis is likely rare among pythons. To understand why it is rare, I used an artificial model to demonstrate that energetic costs to the female likely outweigh thermal benefits to the clutch in species that do not inhabit cooler latitudes or lack large energy reserves. In combination with other studies, these results show that facultative thermogenesis during brooding in pythons likely requires particular ecological and physiological factors for its evolution.
ContributorsBrashears, Jake (Author) / DeNardo, Dale (Thesis advisor) / Harrison, Jon (Committee member) / Deviche, Pierre (Committee member) / McGraw, Kevin (Committee member) / Smith, Andrew (Committee member) / Arizona State University (Publisher)
Created2012
Description
There is considerable recent interest in the dynamic nature of immune function in the context of an animal’s internal and external environment. An important focus within this field of ecoimmunology is on how availability of resources such as energy can alter immune function. Water is an additional resource that drives animal development, physiology, and behavior, yet the influence hydration has on immunity has received limited attention. In particular, hydration state may have the greatest potential to drive fluctuations in immunity and other physiological functions in species that live in water-limited environments where they may experience periods of dehydration. To shed light on the sensitivity of immune function to hydration state, I first tested the effect of hydration states (hydrated, dehydrated, and rehydrated) and digestive states on innate immunity in the Gila monster, a desert-dwelling lizard. Though dehydration is often thought to be stressful and, if experienced chronically, likely to decrease immune function, dehydration elicited an increase in immune response in this species, while digestive state had no effect. Next, I tested whether dehydration was indeed stressful, and tested a broader range of immune measures. My findings validated the enhanced innate immunity across additional measures and revealed that Gila monsters lacked a significant stress hormone response during dehydration (though results were suggestive). I next sought to test if life history (in terms of environmental stability) drives these differences in dehydration responses using a comparative approach. I compared four confamilial pairs of squamate species that varied in habitat type within each pair—four species that are adapted to xeric environments and four that are adapted to more mesic environments. No effect of life history was detected between groups, but hydration was a driver of some measures of innate immunity and of stress hormone concentrations in multiple species. Additionally, species that exhibited a stress response to dehydration did not have decreased innate immunity, suggesting these physiological responses may often be decoupled. My dissertation work provides new insight into the relationship between hydration, stress, and immunity, and it may inform future work exploring disease transmission or organismal responses to climate change.
ContributorsMoeller, Karla T (Author) / DeNardo, Dale (Thesis advisor) / Angilletta, Michael (Committee member) / French, Susannah (Committee member) / Rutowski, Ronald (Committee member) / Sabo, John (Committee member) / Arizona State University (Publisher)
Created2016
Description
Desert environments provide considerable challenges to organisms because of high temperatures and limited food and water resources. Accordingly, desert species have behavioral and physiological traits that enable them to cope with these constraints. However, continuing human activity as well as anticipated further changes to the climate and the vegetative community pose a great challenge to such balance between an organism and its environment. This is especially true in the Arabian Desert, where climate conditions are extreme and environmental disturbances substantial. This study combined laboratory and field components to enhance our understanding of dhub (Uromastyx aegyptius) ecophysiology and determine whether habitat protection influences dhub behavior and physiology.
Results of this study showed that while body mass and body condition consistently diminished as the active season progressed, they were both greater in protected habitats compared to non-protected habitats, regardless of season. Dhubs surface activity and total body water decreased while evaporative water loss and body temperature increased as the active season progressed and ambient temperature got hotter. Total body water was also significantly affected by habitat protection.
Overall, this study revealed that, while habitat protection provided more vegetation, it had little effect on seasonal changes in surface activity. While resource availability in protected areas might allow for larger dhub populations, unprotected areas showed similar body morphometrics, activity, and body temperatures. By developing an understanding of how different coping strategies are linked to particular ecological, morphological, and phylogenetic traits, we will be able to make more accurate predictions regarding the vulnerability of species. By combining previous studies pertaining to conservation of protected species with the results of my study, a number of steps in ecosystem management are recommended to help in the preservation of dhubs in the Kuwaiti desert.
Results of this study showed that while body mass and body condition consistently diminished as the active season progressed, they were both greater in protected habitats compared to non-protected habitats, regardless of season. Dhubs surface activity and total body water decreased while evaporative water loss and body temperature increased as the active season progressed and ambient temperature got hotter. Total body water was also significantly affected by habitat protection.
Overall, this study revealed that, while habitat protection provided more vegetation, it had little effect on seasonal changes in surface activity. While resource availability in protected areas might allow for larger dhub populations, unprotected areas showed similar body morphometrics, activity, and body temperatures. By developing an understanding of how different coping strategies are linked to particular ecological, morphological, and phylogenetic traits, we will be able to make more accurate predictions regarding the vulnerability of species. By combining previous studies pertaining to conservation of protected species with the results of my study, a number of steps in ecosystem management are recommended to help in the preservation of dhubs in the Kuwaiti desert.
ContributorsAl-Sayegh, Mohammed (Author) / DeNardo, Dale (Thesis advisor) / Angilletta, Michael (Committee member) / Smith, Andrew (Committee member) / Sabo, John (Committee member) / Majeed, Qais (Committee member) / Arizona State University (Publisher)
Created2017
Description
An organism's ability to maintain optimal body temperature is extremely important for sustaining physiological and behavioral processes necessary for survival. However, like other physiological systems, thermobiology can be influenced by the availability of resources. Water is a vital resource that has profound implications on many aspects of biological function, including thermoregulatory pathways. However, water availability has a tendency fluctuate within any given ecosystem. While several studies have investigated the influence of water availability on a range of thermoregulatory pathways, very little attention has been given to its influence on Voluntary Maximum Temperature (VMT). We investigated the effects of dehydration on Voluntary Maximum Temperature in a captive population of Gila monsters (Heloderma suspectum). Gila monsters are large-bodied, desert dwelling lizards that experience periods of seasonal dehydration. Additionally, the effects of dehydration on their physiology and behavior have been extensively studied. We hypothesized that dehydration would reduce VMT. As expected, there was a significant decrease in exit temperature as blood osmolality increased. This is presumed to be in an effort to decrease water loss. Adaptations that allow desert dwelling organisms to conserve water are highly advantageous due to seasonal water constraints. Our findings offer insight on how the behavior of these organisms may change in response to changes in climate.
ContributorsHartson, Callie Elizabeth (Author) / DeNardo, Dale (Thesis director) / Angilletta, Michael (Committee member) / Camacho, Agus (Committee member) / School of Life Sciences (Contributor) / School of Human Evolution and Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
This 15-week long course is designed to introduce students, specifically in Arizona, to basic sustainability and conservation principles in the context of local reptile wildlife. Throughout the course, the students work on identifying the problem, creating visions for the desired future, and finally developing a strategy to help with reptile species survival in the valley. Research shows that animals in the classroom have led to improved academic success for students. Thus, through creating this course I was able to combine conservation and sustainability curriculum with real-life animals whose survival is directly being affected in the valley. My hope is that this course will help students identify a newfound passion and call to action to protect native wildlife. The more awareness and actionable knowledge which can be brought to students in Arizona about challenges to species survival the more likely we are to see a change in the future and a stronger sense of urgency for protecting wildlife. In order to accomplish these goals, the curriculum was developed to begin with basic concepts of species needs such as food and shelter and basic principles of sustainability. As the course progresses the students analyze current challenges reptile wildlife faces, like urban sprawl, and explore options to address these challenges. The course concludes with a pilot pitch where students present their solution projects to the school.
ContributorsGoethe, Emma Rae (Author) / Brundiers, Katja (Thesis director) / Bouges, Olivia (Committee member) / School of Sustainability (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Deserts are natural laboratories in which to study the acute effects of extreme heat and aridity on animal physiology, as well as the physiological adaptations that these animals develop to survive. For small, endothermic fliers in the desert, heat balance and water balance are challenging due to high surface area to volume ratios and the additional heat load imposed as a result of endothermy. Much of the previous fifty years of thermo- and hydroregulation research has focused on larger, charismatic megafauna; extremophiles; or only part of the heat or water balance story. Here, I calculate the first heat budget for an important desert bee, Centris caesalpiniae. As is common in many mammals, avians, and other flying insects, I find that C. caesalpiniae males use an appendage – in this case the abdomen – as a convective radiator to dispel excess heat produced by the thoracic flight muscles at high air temperatures. The few heat budgets measured for flying endotherms are conducted in the shade so as to eliminate the effects of solar radiation. To further refine the accuracy of my heat budget model, I consider how heat gain from solar radiation affects the thermal balance of flying desert endotherms. To this effect, I find that solar radiation contributes 43 to 54% of the total heat gain of a desert Centris pallida bee. I additionally show that large morph male, small morph male, and female C. pallida, use different thermoregulatory tactics while flying in shaded versus sunny conditions; large males and females rely on the abdominal convector in the sun while small morph males increase convective conductance in the sun, but do not use an abdominal convector. Given that evaporative cooling was not a significant part of the heat budget for neither C. caesalpiniae nor C. pallida, I investigated the effects of water loss rates and critical thermal maxima during flight on duration of activity period. I found that male C. caesalpiniae limited their activity period due to high water loss rates rather than overheating, and that Centris critical water contents ranged from 48 to 54%, limiting flight activity to about 3 hours.
ContributorsJohnson, Meredith Grace (Author) / Harrison, Jon F. (Thesis advisor) / Buchmann, Stephen (Committee member) / DeNardo, Dale (Committee member) / Dillon, Michael (Committee member) / Arizona State University (Publisher)
Created2023
Description
Desert ecosystems of the southwest United States are characterized by hot and arid climates, but hibernating bats can be found at high altitudes. The emerging fungal infection, white-nose syndrome, causes mortality in hibernating bat populations across eastern North America and the pathogen is increasingly observed in western regions. However, little is known about the ecology of hibernating bats in the southwest, which can help predict how these populations may respond to the fungus. My study investigated hibernating bats during two winters (2018-2019/2019-2020) at three caves in northern Arizona to: (1) describe diversity and abundance of hibernating bats using visual internal surveys and photographic documentation, (2) determine the duration of hibernation by recording bat echolocation call sequences outside caves and recording bat activity in caves using visual inspection, and (3) describe environmental conditions where hibernating bats are roosting. Adjacent to bats, I collected temperature and relative humidity, which I converted into absolute humidity. I documented hibernation status (i.e. active vs. not active) and roosting body position (i.e. open, partially hidden, and hidden). Between September 2018 and April 2019, 246 bat observations were recorded across the three caves. The majority of bats were identified as Myotis spp. (45.9\%, n=113), followed by Corynorhinus townsendii (45.5\%, n=112), Parastrellus hesperus (4.8\%, n=12), Eptesicus fuscus (3.6\%, n=9). Between September 2019 and April 2020, I documented a total of 361 bat observations across the three caves. C. townsendii was most prevalent (52.9\%, n=191), followed by the category P. hesperus/Myotis spp. (25.7\%, n=93), Myotis spp. (12.4\%, n=45), P. Hesperus (4.4\%, n=16), E. fuscus (3.6\%, n=13) and Unknown (0.8\%, n=3). Average conditions adjacent to bats were, temperature=12.5ºC, relative humidity=53\%, and absolute humidity=4.9 g/kg. Hibernating bats were never observed in large clusters and the maximum hibernating population size was 24, suggesting low risk for pathogen transmission among bats. Hibernation lasted approximately 120 days, with minimal activity documented inside and outside caves. Hibernating bats in northern Arizona may be at low risk for white-nose syndrome based on population size, hibernation length, roosting behavior, and absolute humidity, but other variables (e.g. temperature) indicate the potential for white-nose syndrome impacts on these populations.
ContributorsMaldonado Perez, Nubia Erandi (Author) / Moore, Marianne S (Thesis advisor) / DeNardo, Dale (Committee member) / Deviche, Pierre (Committee member) / Smith, Brian (Committee member) / Arizona State University (Publisher)
Created2020
Description
I examined how competition affects the way animals use thermal resources to control their body temperature. Currently, biologists use a cost benefit analysis to predict how animals should regulate their body temperature. This current theory of thermoregulation does not adequately predict how animals thermoregulate in the wild. While the model works well for animals in low cost habitats, it does not work as well for animals in high cost habitats. For example, animals that are in habitats of low thermal quality thermoregulate more precisely than predicted by the current model. One reason these predictions may be wrong is that they do not account for interactions between animals. By including these interactions in future predictions, a more accurate model of thermoregulatory behavior can be created.
Before developing a theory for all animals, a model needs to be developed for a single model animal, such as fruit flies, that can be used to empirically examine how organisms thermoregulate under competition. My work examines how flies behave around other flies and develops a game theory model predicting how they should optimally behave. More specifically, my research accounts for competition among larvae by using game theory to predict how mothers should select sites when laying eggs. Although flies prefer to lay their eggs in places that will offer suitable temperatures for the development of their larvae, these sites become less suitable when crowded. Therefore, at some density of eggs, cooler sites should become equally beneficial to larvae when considering both temperature and competition. Given this tradeoff, an evolutionarily stable strategy (ESS) emerges where some flies should lay eggs in cooler sites while other flies should lay eggs at the warmer temperature. By looking at the fitness of genotypes in habitats of differing quality (competition, temperature, food quality, space), I modeled the ESS for flies laying eggs in a heterogeneous environment. I then tested these predictions by observing how flies compete for patches with different temperatures.
Before developing a theory for all animals, a model needs to be developed for a single model animal, such as fruit flies, that can be used to empirically examine how organisms thermoregulate under competition. My work examines how flies behave around other flies and develops a game theory model predicting how they should optimally behave. More specifically, my research accounts for competition among larvae by using game theory to predict how mothers should select sites when laying eggs. Although flies prefer to lay their eggs in places that will offer suitable temperatures for the development of their larvae, these sites become less suitable when crowded. Therefore, at some density of eggs, cooler sites should become equally beneficial to larvae when considering both temperature and competition. Given this tradeoff, an evolutionarily stable strategy (ESS) emerges where some flies should lay eggs in cooler sites while other flies should lay eggs at the warmer temperature. By looking at the fitness of genotypes in habitats of differing quality (competition, temperature, food quality, space), I modeled the ESS for flies laying eggs in a heterogeneous environment. I then tested these predictions by observing how flies compete for patches with different temperatures.
ContributorsBorchert, Jason (Author) / Angilletta Jr., Michael (Thesis advisor) / Pratt, Stephen (Committee member) / Harrison, Jon (Committee member) / DeNardo, Dale (Committee member) / Mitchell, William (Committee member) / Arizona State University (Publisher)
Created2018