OU - Dissertations

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Open Access
Activity metabolism in the mudpuppy, Necturus maculosus.
(1978) Miller, Kirk,
Open Access
Acute toxicity of hydrogen sulfide to fish during harvesting operations on commercial catfish farms :
(1980) Torrans, Eugene Leslie,
Unconsumed fish food apparently resulted in the high sulfide concentrations seen near the feeding area in May or June and September of both years. Dissolved sulfide concentrations decreased near the feeding area in July and August, when the water temperatures were over 28(DEGREES)C and the fish consumed nearly all of the food given. The direct effect of unconsumed food on dissolved sulfide was limited to the vicinity of the feeding area.
Open Access
Aerial versus aquatic gas exchange in salamanders in response to environmental hypercapnia /
(1984) Braun, Beth A.,
All animals, acclimated at 20(DEGREES)C and LD 12:12, were subjected to a 3 hr control period of normoxic normocapnia in both media. Necturus was then exposed to aquatic hypercapnia of P(, CO(, 2)) = 20-130 mm Hg, and the P(, O(, 2)) of this solution elevated to that at the beginning of the control period (150 mm Hg). While none of the animals registered pulmonary CO(, 2) release during the control period, 6 out of the 16 did so during hypercapnia. This contribution of the lungs to overall gas exchange was, however, extremely small; it did not fall into a regular pattern in any animal. Thus, aquatic hypercapnia did not result in a shift in CO(, 2) release from gills and skin to lungs.
Open Access
THE ALAN SHEPARD (SHEP) GENE REGULATES NEURONAL REMODELING DURING METAMORPHOSIS
(2014) Chen, Dahong; Hewes, Randall; Holt, Ben; Durica, David; McCauley, David; Masly, JP
Peptidergic neurons are a group of neuronal cells that synthesize and secrete peptides to regulate a variety of biological processes. To identify genes controlling the development and function of peptidergic neurons, our lab conducted a screen of 545 splice-trap lines and identified 28 loci that drove expression in peptidergic neurons when crossed to a GFP reporter transgene. Based on these expression pattern results, I selected the alan shepard (shep) gene for further study since an insertion in shep drove expression specifically in most peptidergic neurons. shep transcripts and SHEP proteins were detected primarily and broadly in the central nervous system (CNS) in embryos, and this expression continued into the adult stage. Loss of shep resulted in late pupal lethality, reduced adult life span, wing expansion defects, uncoordinated adult locomotor activities, rejection of males by virgin females, and reduced neuropil area and reduced levels of multiple pre-synaptic markers throughout the adult CNS. Examination of the bursicon neurons in shep mutant pharate adults revealed smaller somata and fewer axonal branches and boutons, and all of these cellular phenotypes were fully rescued by expression of the most abundant wild-type shep isoform. In contrast to shep mutant animals at the pharate adult stage, shep mutant larvae displayed normal bursicon neuron morphologies. Similarly, shep mutant adults were uncoordinated and weak, while shep mutant larvae displayed largely, though not entirely, normal locomotor behavior. Thus, shep played an important role in the metamorphic development of many neurons. To shed light on the molecular mechanisms by which SHEP regulates metamorphic outgrowth of neurons, I conducted a genetic modifier screen for shep suppressors. I screened a total of 702 deficiencies that covered 86% of the euchromatic genes, and isolated 33 deficiencies as candidate suppressors. From this set, I identified 12 deficiencies that partially suppressed the morphological defects seen in shep mutant bursicon neurons. RNAi tests and crosses with mutant alleles for individual genes led to the identification of Daughters against dpp (Dad) and Olig family (Oli) as shep suppressor genes, and both rescued neurites of the bursicon neuron in the subesophageal ganglia. Oli encodes a transcription factor with unknown downstream targets. Dad encodes an inhibitory Smad protein that inhibits phosphorylation of R-Smad by activated Bone morphogenetic protein (BMP) receptors, thus implicating BMP signaling in the control of neurite outgrowth from the bursicon neurons during metamorphosis. In addition, I found that the su(Hw) gene, which encodes a gypsy insulator protein that is known to interact with SHEP, suppressed the wing expansion defects caused by loss of shep, although I did not observe rescue of bursicon neuron outgrowth by su(Hw). These findings highlight novel genetic interactions that are important for controlling neurite growth in mature, terminally differentiated neurons.
Open Access
AN ENHANCER-TRAP AND SPLICE-TRAP SCREEN FOR REGULATORS OF ENDOCRINE FUNCTIONS IN THE CENTRAL NERVOUS SYSTEM AND THE EPITRACHEAL GLAND OF DROSOPHILA MELANOGASTER
(2010) Qu, Chunjing; Hewes, Randall S
Peptide hormones play important roles in a wide variety of biological processes, such as learning and memory, body weight homeostasis, circadian rhythms, and addiction. In Drosophila, over 20 peptide hormones are produced in the central nervous system (CNS) by distinct groups of specialized neurons, peptidergic neurons. Another important endocrine function is performed by the Inka cell, responsible for the production and secretion of the ecdysis triggering hormone (ETH), which is critical for the ecdysis process of the animal. Although many genes encoding peptide hormones have been identified, our knowledge about factors that regulate the production and secretion of peptide hormones is still very limited. In order to identify more endocrine regulators, we performed an enhancer trap and splice trap screen for genes that are expressed in peptidergic neurons in the CNS and the epitracheal gland, where the ETH-expressing Inka cell is located. From a screen of 545 splice trap lines and 287 enhancer trap lines, we obtained 28 insertions in 25 genes that are expressed in peptidergic neurons of the CNS, and 14 insertions in 14 genes that are expressed in the epitracheal gland. For lines that are expressed in the CNS, we further mapped the expression patterns by immunostaining with antisera to several neuropeptides, including Bursicon, Drosophila insulin-like peptide 2, crustacean cardioactive peptide, and leucokinin, each of which is expressed in distinct groups of neurons. Among the 28 lines identified, the BG00836 insertion in the gene alan shepard (shep) was extremely interesting to us because of its restricted reporter gene expression in peptidergic neurons. shepBG00836 mutant adults showed defects in wing expansion and decreased resistance to starvation, and these phenotypes were reverted by precise excision of the P element. However, it was later shown that these may be neomorphic phenotypes brought by the combination of the shep mutation and unknown factors in the genetic background. Follow-up experiments on shep showed that it is involved in the control of neurite outgrowth in the CNS. Therefore, shep may function as a general developmental regulator for peptidergic neurons. Lines with reporter gene expression in the epitracheal glands may reveal genes that participate in the regulation of ETH expression or secretion. We examined the functions of the trapped loci by knocking down gene expression specifically in the Inka cells with transgenic RNA interference (RNAi). Expression of UAS-taiman (tai)RNAi in the Inka cells led to ecdysis defects and reduced ETH expression. TAI is a known ecdysone receptor coactivator, and expression levels of TAI were correlated with the circulating steroid hormone titer. Previous research results in our lab and the Cherbas lab suggested that the basic-leucine zipper transcription factor Cryptocephal (CRC) and the EcR/USP heterodimeric ecdysone receptor together form a complex on the ETH promoter and activate the expression of ETH. Based on these findings, we propose a model in which a complex of TAI, CRC, and EcR/USP binds to the ETH promoter and activates ETH transcription.
Open Access
An analysis of the activation of the adipogenic differentiation pathway in the bone marrow stroma by members of the nuclear hormone receptor family.
(1997) Robinson, Claudius Emet.; Dorica, David S.,; Gimble, Jeffrey M.,
The bone marrow stroma is composed of a diverse array of cell types that have unique functions. Of the different types, the adipocyte is the most abundant. It is not clear what purpose adipocytes serve in the bone marrow. They may simply occupy space in the marrow cavity or they may play active roles in systemic lipid metabolism and provide an energy reservoir in the bone marrow. Marrow adipocytes also appear to contribute growth factors and cytokines that directly promote hematopoiesis and influence osteogenesis. The enzyme lipoprotein lipase (LPL) is an early marker of adipogenesis and its regulation is complex. It is the enzyme responsible for the hydrolysis of triglycerides into free fatty acids and the clearance of chylomicrons from the blood. It is regulated by a variety of transcription factors. The nuclear hormone receptor superfamily consists of an immense number of genes and is accepted as the largest transcription factor family in eukaryotes. We determine that peroxisome proliferator activated receptors (PPARs) with their ligands induce adipogenesis in bone marrow stromal cells and that they bind and activate the LPL gene promoter in vitro. The chicken ovalbumin upstream promoter transcription factors (Coup-TFs) are orphan receptors that bind certain DNA direct repeats as homodimers and heterodimers with other steroid receptor molecules such as the retinoid X receptor (RXR) and are accepted as repressors of other nuclear hormone receptors. We determine that Coup-TFs bind the LPL promoter in vitro and demonstrate in cotransfection analysis that they act in concert with the PPAR$\gamma$2 and RXR$\alpha$ proteins to multiplicatively activate its transcription. Recently, new regulatory proteins have been described that affect the interaction of nuclear hormone receptors with the transcriptional apparatus. We determine that the co-regulators of nuclear hormone receptors SMRT (silencing mediator for retinoid and thyroid-hormone receptors) and steroid receptor coactivator (SRC-1) help regulate the LPL promoter in conjunction with PPAR$\gamma$2, RXR$\alpha$ and Coup-TFII (ARP-1) in negative and positive fashion respectively. Improved understanding of the mechanisms regulating stromal adipocyte differentiation may lead to therapeutic interventions that can enhance osteogenesis and hematopoiesis in afflicted individuals.
Open Access
Ants in Flight: Reproduction, Dispersal and Predation of Ant Queens
(2016-05) Helms, Jackson; Bridge, Eli; Hoagland, Bruce; Marsh-Matthews, Edie; Patten, Michael; Vaughn, Caryn
Flying animals, especially insects, are a prominent feature of most terrestrial environments and make up a majority of the world’s known species. The biomechanical demands of flight shape the biology of flying insects at all levels, including their physiology, life history, and interactions with other organisms. Many social insects live in colonies consisting primarily of wingless workers, where the ability to fly is restricted to specialized castes. In most ant species, reproductive queens have wings and fly to leave their nest, mate, and found colonies. Here I investigate the role of flight in ant biology, starting with first principles of flight mechanics and physiology, building to the evolution of different life histories, and finishing with the value of queens as prey for aerial predators, the distribution of ants in the atmosphere, and the spread of invasive species across landscapes. In Chapter 1 I investigate a potential tradeoff (the Found or Fly hypothesis) that ant queens experience between flight and reproduction. I do this by examining variation in flight morphology within a single species, the tropical cavity-nesting ant, Azteca instabilis. Queens of this species vary substantially in abdomen weight throughout the year. Heavier abdomens contain larger nutrient reserves that help young queens rear worker offspring and found new colonies. But they also incur a cost in flight morphology, by reducing flight muscle ratios and increasing wing loading and the drag experienced during flight. Chapter 2 asks whether the Found or Fly tradeoff applies at an evolutionary level among species. By comparing queens of 21 species from a community in Panama, I find that flight ability is tied to reproductive strategy. Claustral species—those which fuel colony founding entirely through their abdominal nutrient reserves—have heavier abdomens and lower flight muscle ratios. Claustral species avoid adverse effects on wing loading, however, by evolving larger wings. Several claustral species have flight muscle ratios at or below the theoretical limits for insect flight, and may have adaptations for load-carrying. Queens that have access to external sources of nutrition during colony founding, on the other hand, such as social parasites, fungus-gardeners, and those that hunt their own prey, have lighter abdomens and high flight muscle ratios. Chapter 3 applies these insights to alternate queen castes within the same species, and attempts to relate flight morphology to performance through a live flight experiment. I examine the flight morphology of two fire ant species that co-occur along the U.S. Gulf Coast—the invasive Red Imported Fire Ant (Solenopsis invicta) and the native Tropical Fire Ant (S. geminata). In both species, colonies produce both heavy claustral queens and light parasitic queens. Among claustral S. invicta queens, individuals with lighter abdomens can fly for longer periods of time. When comparing queen types, claustral queens of both species have heavier abdomens, lower flight muscle ratios, higher wing loading, and higher drag than their parasitic counterparts. In S. geminata, claustral queens also have larger wings, offsetting some of the adverse wing loading effects and mirroring interspecific patterns. The next two chapters address what happens to ant queens once they enter the atmosphere on their mating flights. I attach altitude logging devices to Purple Martins (Progne subis), a bird that preys on insects it captures during flight, and monitor the prey they deliver to their young. In so doing I discover (Chapter 4) that Purple Martins in Oklahoma feed primarily on invasive Red Imported Fire Ant queens, and double their foraging efficiency by doing so. I calculate that across the southern USA, Purple Martins probably eat billions of fire ant queens each year. I also measure the flight altitudes of ants and other insects (Chapter 5), and find that heavier ants fly at lower altitudes in the atmosphere, consistent with the Found or Fly tradeoff. Finally, in Chapter 6 I develop a computer model to simulate the dispersal and reproduction of Red Imported Fire Ants introduced to a novel environment. In the simulations, hypothetical fire ant populations that invest more heavily in parasitic queens, and less in claustral queens, experience larger average colony sizes, higher habitat occupancy, and slower range expansion. When investigating the optimal investment by a reproductive colony, I find that colonies at an expanding range edge benefit more by investing almost entirely in claustral daughter queens, while those in the interior of a range benefit by investing more heavily in parasitic daughters. The two divergent selection regimes may play a role in the evolution of alternate reproductive strategies in ants.
Open Access
Aspects of respiratory adaptation in the bowfin, Amia calva.
(1978) Perry, John William,
Open Access
Aversive learning effect on odor coding in rat's piriform cortex
(2011) CHEN, CHIEN-FU FRED; Wilson, Donald A||Berkowitz, Ari
Olfaction, a sense for detecting and discriminating chemical molecules in the environment, is critical for animal survival, reproduction and other adaptive behaviors. The olfactory system is organized in three major stations (a sensor sheet, an initial processing and projection unit, and a central processing unit) that are shared across phyla, and has been functioning for millions of years. Since Buck and Axel identified a multigene family for coding the olfactory receptors, knowledge of the olfactory system has quickly accumulated in the last 20 years. This allows us to investigate fundamental questions in olfaction, including how odor percepts are formed, how olfactory information is used and stored, and how experiences shape olfactory perception in our daily life.
Open Access
Aversive learning effect on odor coding in rat's piriform cortex
(2011) CHEN, CHIEN-FU FRED; Wilson, Donald A||Berkowitz, Ari
Olfaction, a sense for detecting and discriminating chemical molecules in the environment, is critical for animal survival, reproduction and other adaptive behaviors. The olfactory system is organized in three major stations (a sensor sheet, an initial processing and projection unit, and a central processing unit) that are shared across phyla, and has been functioning for millions of years. Since Buck and Axel identified a multigene family for coding the olfactory receptors, knowledge of the olfactory system has quickly accumulated in the last 20 years. This allows us to investigate fundamental questions in olfaction, including how odor percepts are formed, how olfactory information is used and stored, and how experiences shape olfactory perception in our daily life.
Open Access
Biophysical mechanisms for the generation of electrosensory and communication signal in the weakly electric fish Eigenmannia virescens
(2018-05-03) Ban, Yue; Markham, Michael; Berkowitz, Ari; Masly, John; Lemon, Christian; Bartley, Laura
The weakly electric fish Eigenmannia virescens generates electric organ discharges (EODs) to navigate and communicate. The EODs are brief monophasic voltage pulses with brief inter-pulse intervals, resulting in a sinusoidal waveform. EODs are produced by the simultaneous action potentials (APs) of ~1000 electric organ (EO) cells (electrocytes). Electrocytes generate APs at steady frequencies of 200-600 Hz with Na+ currents that exceed 10 microamperes during each AP, creating large energetic demands. The aim of this study was to investigate the biophysical mechanisms that allow fast spiking and manage the large ionic currents in electroctyes. E.virescens elecrocytes initiate the AP using voltage-gated Na+ (Nav) channels and terminate the AP using Na+-activated K+ (KNa) channels, rather than voltage-gated K+ (Kv) channels, as is the case in other electric fish where electrophysiological data are available. The characteristics of K+ channels are key determinants of an excitable cell’s firing pattern. Using degenerate PCR and RACE-PCR, I identified the presence of three types of KNa channel subunit in electrocytes, eSlack1 and eSlick, closely related to KNa channel subunits in other vertebrates, and a shorter isoform, eSlack2. Whole-cell currents recorded from Xenopus laevis oocytes expressing these KNa channels revealed that eSlack1 and eSlick can form functional homomeric K+ channels and eSlick currents activated much more rapidly than eSlack1 currents. eSlack2 could not form functional homomeric ion channels, even though the subunits could be successfully trafficked to the plasma membrane. To investigate how ion channels coordinate to generate high-frequency APs, I studied the expression pattern of ion channels and Na+/K+ ATPases using immunohistochemistry and by expressing fluorescent protein-tagged ion channels in electrocytes. Cholinergic receptors and Nav channels are only localized on the posterior side, while all K+ channels including the three KNa channel subunits and the ATP sensitive Kir6.2 are expressed on the anterior side. Na+/K+ ATPases are widely distributed on both the posterior and anterior membranes. Two-photon 3D imaging of electrocytes showed the cell’s posterior membrane is densely occupied by narrow invaginations providing extensive surface area for the expression of Na+ channels and Na+/K+ ATPases to manage the large ionic currents. Abundant vesicles were present underneath the posterior membrane, which may be associated with the trafficking of Na+ channels and Na+/K+ ATPases to the plasma membrane when the amplitude of AP is under modulation. Finally, I investigated the ionic mechanisms associated with variations in AP frequency in the fast-spiking electrocytes by measuring the transcription levels of ion channels and ion transporters in EO from fish with different EOD frequencies. EOD frequency is correlated with the transcription levels of Nav1.4a, the fast-activating Slick KNa channel subunits, Kir6.2 and Na+/K+ ATPases but not Nav1.4b, eSlack1 and eSlack2. In summary, the fast-activating Slick KNa channels are expressed exclusively in electrocytes to support the generation of sustained high-frequency APs. Among all the ion channels and ion transporters expressed in electrocytes, only Slick KNa channels, Nav1.4a, and Na+/K+ ATPases are associated with increased excitability, and these transcripts are expressed predominantly in electrocytes when compared to skeletal muscle. Variations in the transcription levels of eSlick, Nav1.4a and Na+/K+ ATPases are positively correlated with individual differences in EODf, where they likely contribute to the capacity for high-frequency firing.
Open Access
Cambrian [Marjuman] trilobites (Arthropoda) of the Cow Head, western Newfoundland.
(2005) Dengler, Alyce A.; Cifelli, Richard,; Westrop, Stephen,
Conglomerates consisting of shelf-derived limestone boulders in debris flows form the fossiliferous strata of the Cow Head Group on the west coast of Newfoundland. These conglomerates have yielded in excess of 20,000 trilobites dated from mid-Cambrian into Ordovician. This study examines 1500 specimens of those trilobites in the order Ptychopariida from the earliest Upper Cambrian, the Marjuman. The Upper and Lower Marjuman are distinctly different, with only 3 genera appearing in both. Each boulder comprises a separate collection and the faunas of most are unique.
Open Access
THE CENTRAL PATTERN GENERATORS FOR SWIMMING AND SCRATCHING ARE PARTLY SHARED OR INTERACT AT THE INTERNEURONAL LEVEL IN ADULT TURTLES.
(2014-12) Hao, Zhaozhe; Berkowitz, Ari; Hewes, Randall; Knapp, Rosemary; Markham, Michael; Wirsig-Wiechmann, Celeste
Distinct rhythmic behaviors involving a common set of motoneurons and muscles can be generated by separate central nervous system networks, a single network, or partly overlapping networks in invertebrates. Less is known for vertebrates. Does the spinal cord use a single network to generate distinct rhythms or two separate networks? The turtle spinal cord contains networks that generate swimming as well as three forms of scratching (rostral, pocket, and caudal) with three different knee-hip synergies. First, I directly compared the adequacy of rostral segments in generating swimming and scratching. I separated caudal segments from immobilized, low-spinal turtles by sequential spinal cord transections. After the separation of the caudal four segments of the five-segment hindlimb enlargement, the remaining enlargement segment and five pre-enlargement segments still produced rhythms for forward swimming and both rostral and pocket scratching. The swimming rhythm frequency was usually maintained. Some animals continued to generate swimming and scratching rhythms even with no enlargement segments remaining, using only pre-enlargement segments. The pre- enlargement segments and rostral-most enlargement segment were also sufficient to maintain hip flexor (HF) motoneuron quiescence between HF bursts, which normally occurs during each hip extensor (HE) phase, during swimming. In contrast, the HF- quiescent phase was increasingly absent (i.e., HE-phase deletions) during rostral and pocket scratching. Moreover, respiratory motoneurons that normally burst during HE bursts continued to burst during the HF quiescence of swimming even with the caudal segments separated. Thus, the same segments are sufficient to generate the basic rhythms for both locomotion and scratching. These segments are also sufficient to produce a reliable HE phase during locomotion but not during rostral or pocket scratching. I hypothesize that the rostral HE-phase interneurons that rhythmically inhibit HF motoneurons and interneurons are sufficient to generate HF quiescence during HE-biased swimming, but not during the more HF-biased rostral and pocket scratching. I then simultaneously activated two networks to reveal overlap or interactions between them. The simultaneous stimulation for forward swimming and each form of scratching could 1) increase the rhythm frequency; 2) evoke switches, hybrids, and intermediate motor patterns; 3) reconstruct a swim motor pattern when the swim stimulation was subthreshold, and 4) disrupt rhythm generation entirely. The strength of swim stimulation could influence which effect was obtained. Thus, even pocket scratching and caudal scratching, which do not share a knee-hip synergy with forward swimming, can interact with swim stimulation to alter both rhythm and pattern generation. Collectively, these findings suggest that the spinal cord networks that generate locomotion and scratching have important shared components or strong interactions between them. If the latter, interactions could occur in motoneurons themselves or earlier, in spinal interneurons. I thus recorded intracellularly from hindlimb motoneurons during dual stimulation. Motoneuron membrane potentials displayed a regular oscillation at a higher frequency than during swim or scratch alone. In contrast, arithmetic addition of the oscillations during swimming alone and scratching alone with various delays always generated irregular oscillations. Also, the standard deviation of the dual-referent phase-normalized membrane potential was similar during dual stimulation and swimming or scratching alone. In contrast, the standard deviation was greater when pooling cycles of swimming alone and scratching alone. This shows that dual stimulation generates a single rhythm prior to motoneurons. In conclusion, either swimming and scratching share a rhythm generator or the two rhythms are integrated into one by interneurons.
Open Access
Community ecology of water-filled tree holes in Panama.
(1999) Yanoviak, Stephen Paul.; Fincke, Ola M.,
Water-filled tree holes are phytotelmata formed when rain collects in branch crotches and other wood-lined cavities. Repeated surveys of natural and artificial water-filled tree holes on Barro Colorado Island (BCI), Panama, (1994--1998) revealed 59 species of macroorganisms associated with this habitat. A typical hole contained 5 or 6 macroorganism species, but up to 14 taxa occurred in some holes. Total macroorganism abundance and species richness increased with hole volume. Species richness in both natural and artificial holes declined with increasing height above the ground. Macroorganism abundance and species richness were not correlated with pH, conductivity or dissolved oxygen content of tree hole water. Microvelia cavicol, a new species discovered in BCI tree holes generally occurred in the same holes throughout the wet season and in successive years. Hole size and shape were the best predictors of its abundance. Leaves from different tree species decomposed at different rates and degraded faster when grazers were present. Pupation success was highest for mosquito larvae reared on Platypodium litter in the tab. Similar results were obtained in the field, where macroorganism species richness and persistence times were greatest in artificial holes containing Platypodium litter. Litter decomposition rates were faster in the presence of mosquitoes, and odonates reduced mosquito survival. Predators had no indirect effect on litter decomposition. Small mosquito larvae apparently escaped predation and maintained a significant grazer effect on litter decay rates in the presence of odonates. Fewer species existed in holes containing large odonates vs. holes from which odonates were excluded. Selective predation is probably responsible for this pattern. Standardized litter addition increased mean species richness in tree holes, whereas litter removal reduced mean richness. Effects of litter manipulations disappeared five weeks after treatments were terminated. In artificial tree holes, litter quantities affected macroorganism abundance and species richness, but only during the first three weeks. Addition of an odonate larva on Week 3 had no effect on abundance, but reduced species richness during the subsequent four weeks.
Open Access
Comparative physiology and macroecology of thermal tolerance in ectothermic vertebrates with correlates of phylogeny and biogeography.
(1997) Lutterschmidt, William Isaac.; Hutchison, Victor H.,
An organism's distribution and geographic range result from physiological tolerances and its ability to adjust physiological processes to maximize survival, growth, and reproduction under a diversity of environmental factors characteristic to its geographic region. This principle has been described by Liebig's Law of the Minimum which states that the distribution of species is governed by the environmental factor for which a species has the narrowest tolerance range or least adaptability. As described, physiological ecologists agree that temperature is probably one of the most pervasive factors in determining the distribution of animals. In this work, I address the importance of species specific thermal tolerance in an attempt to explain some macroecological patterns of distribution among fishes. The first two chapters are an evaluation and review of thermal tolerance in studies of comparative physiology. I measured the critical thermal maximum (CTMax) for more than 600 individuals to statistically evaluate the variability associated with the end points loss of righting response (LRR) and onset of spasms (OS) used in determining CTMax. In my review of thermal tolerance, I found 388 of 725 papers to provide data for a historical and taxonomic review with a discussion of various methodologies and uses for the measure of species specific thermal tolerance.
Open Access
CONSEQUENCES OF HABITAT TRANSITIONS ON LOCOMOTIVE TRAIT DIVERSIFICATION AT THE MICRO- AND MACRO-EVOLUTIONARY SCALES
(2015-05-08) Cureton, James II; Broughton, Richard; Holt, Ben III; Matthews, William; Masly, John; Wellborn, Gary
Contemporarily evolving systems provide a unique opportunity to characterize the direction, pattern, and rates of phenotypic change among multiple species. The damming of streams to create reservoirs results in a change from lotic to lentic environments and induces the evolution of phenotypes that optimize unsteady swimming performance in fishes. In my first chapter, I examined the spatial and temporal patterns of evolution of body shape in a widespread North American stream fish (Pimephales vigilax) in response to stream impoundment. I observed significant changes in body depth, head shape, and fin placement following dam construction in each of seven different Oklahoma rivers. The magnitude of change was greatest in the first 15 generations post-impoundment, followed by continued but more gradual change thereafter. In my second chapter, I compare the direction and rate of evolution of body size, body shape, and caudal fin shape following stream impoundment in eight cyprinids. My data show that these traits do not diverge in the same direction in all species. Rates of evolution during the period of directional selection were consistent among traits and species, perhaps due to similar amounts of underlying quantitative genetic variation as a result of their recent common ancestry. All of the above results indicate that changes in environmental conditions can result in rapid evolution of functionally important traits. In my third chapter, I tested the hypothesis that transitions between benthic and pelagic habitats resulted in convergent evolution of body shape in North American cyprinids. I built a phylogenetic hypothesis of 201 species using four genes, reconstructed the evolution of habitat type on the recovered topology, and evaluated evolution of body shape in benthic and pelagic species. I detected approximately 25 transitions between benthic and pelagic species with pelagic-to-benthic transitions being most common. Body shape was significantly different between benthic and pelagic species with benthic species developing deeper bodies with larger heads than pelagic species. However, benthic and pelagic species did not inhabit mutually exclusive regions of morphospace suggesting that convergent evolution of body shape is incomplete in this group of fishes. My results show that habitat transitions can drive convergent evolution of similar phenotypes among distinct evolutionary lineages. However, the magnitude of convergence among different lineages is likely constrained by their unique evolutionary history.
Open Access
CONSERVATION, ECOLOGY, AND EVOLUTION OF MIGRATORY BEHAVIOR IN THE PAINTED BUNTING (Passerina ciris)
(2015) Contina, Andrea; Kelly, Jeffrey; Bridge, Eli; Hoagland, Bruce; Patten, Michael; Smith, Thomas; Weider, Larry
In animal migration studies, determining the migratory connectivity of different species is a crucial step to understand the ecology and evolution of complex behavioral traits as well as to implement effective conservation management plans of declining species. Intrinsic markers, such as stable isotopes and genetic markers, in conjunction with miniaturized light-level geolocator devices, provide high resolution tools to study the ecology and evolution of migration in birds smaller than 20 grams and offer insight on the breeding population of origin of those individuals trapped and sold in the international pet trade market. For example, from 2005 to 2009, CITES documented more than 317,000 live birds sold annually within an industry estimated to be worth billions of US dollars per year. In this context, migratory species can be particularly difficult to protect because any management effort would necessarily involve cooperation among different countries with distinct laws and regulations. A case in point is the Painted Bunting (Passerina ciris), which breeds primarily in the United States and winters in Mexico, Central America, southern Florida, and the Caribbean. I provide a new library of polymorphic microsatellite loci and offer a new tool for genetic population structure studies, forensic analyses, and conservation management of the Painted Bunting and other related species of the genus Passerina. My results suggest that buntings harvested in Central America for the retail market belong to the western breeding population as opposed to the smaller Atlantic breeding population. However, a percentage of both populations come into contact at the wintering grounds in the Yucatan Peninsula where conservation efforts might need to be strengthened.Furthermore, during my investigations on the molting ecology of the Painted Buntings, I found that birds breeding in Oklahoma and molting in Sinaloa, Mexico, show a clear bimodal pattern of stable isotope ratios in their flight feathers, as previously demonstrated in this species, suggesting that some birds may initiate molt immediately upon arrival in northwestern Mexico whereas others may delay molt. I used geologger tags to test whether differences in the timing and route of fall migration movements were related to stable isotope signatures in primary feathers. I observed variation among individuals in migration routes, wherein birds from the same breeding population differed greatly in their use of molting and wintering locations. However, I did not find a relationship between isotope signatures and the timing or route of fall migration.Furthermore, I investigated possible relationships between variation in two candidate genes implicated in the control of migratory behavior (CLOCK and ADCYAP1) and several aspects of fall migration including initiation date, arrival at molt/stopover sites, and duration of the first leg of fall migration. I evaluated the mutation rate of these candidate genes through an Approximate Bayesian Computation (ABC) coalescent approach and studied the effect of natural selection on their allele frequencies across populations. I found that millennial scale summer temperatures and longitude likely affected the current genotypes of CLOCK and ADCYAP1 in three sampling populations. To search for novel genes associated with migratory performance, I implemented 454 next generation sequencing and generated over 48,000 DNA sequences distributed over the Painted Bunting genome. I assembled an extensive library of candidate genes by annotations extracted from the Mouse Genome Informatics database and I focused on the following candidate genes: ADRA1d, ANKRD17, CISH, and MYH7. I tested these genes across avian migratory and non-migratory species, revealing a surprising degree of allelic variation in some genes. MYH7 correlated with speed of migration (km/day) and body mass across 11 species of songbirds in addition to two novel uncharacterized polymorphic genes that strongly correlated with duration of migration in the Painted Buntings.
Open Access
Correlates of extra-pair paternity and the effects of ectoparasites on nestling growth, parental provisioning and reproductive success in the house sparrow.
(2000) Whitekiller, Robin Rae.; Mock, D. W.,; Schwagmeyer, P. L.,
In addition, I looked at another aspect of the reproductive biology of the House Sparrow, the effects of ectoparasites on nestling growth, parental provisioning and reproductive success. To determine whether Pellonyssus reedi, a haematophagous mite, affects offspring growth and fledging success, I compared mass, tarsus length, wing length, duration of the nestling period, and fledging success for nestlings in nests treated with a pesticide to that of young in control nests. To evaluate the effect of P. reedi on parental provisioning, I compared the total number of feeding visits, sizes of prey delivered, and divisions of parental workloads between treatments. Nestlings in pesticide-treated nests had, on average, greater mass and tarsus lengths than nestlings in control nests. Nestlings in pesticide-treated nests also tended to have longer wings. Duration of the nestling period did not differ between the two treatments. I also found no effect on fledging success. Neither total parental feeding rate nor mean prey size delivered differed between treatments, but male parents tended to do a greater share of nestling provisioning at pesticide-treated nests.
Open Access
Cottonmouth (Agkistrodon piscivorus) spatial ecology.
(2005) Roth, Eric David.; Vitt, Laurie J.,
Radio-telemetry was used to study spatial ecology of a Cottonmouth (Agkistrodon piscivorus) population in eastern Texas. I examined effects of sex, reproductive state, and body size on spatial use within a riparian habitat. Snakes inhabited a relatively linear environment, restricting movements to the vicinity of the stream. Males occupied larger home ranges than both gravid and non-gravid females. Gravid females exhibited marginally larger home ranges than non-gravid females, but any effects attributable to reproductive state were relatively small when compared to sex differences in spatial use. Body size was positively correlated with home range size but did not account for observed home range differences among population subunits.
Open Access
Critical thermal maxima and thermal tolerance in small mammals.
(1981) Erskine, Dale James,
The CTM was then used to compare the thermal tolerances of five species of small mammals (laboratory mice, Mus musculus; white-footed mice, Peromyscus leucopus; gerbils, Meriones unguiculatus; laboratory rats, Rattus norvegicus; kangaroo rats, Dipodomys ordi). All animals were acclimatized to 25 (+OR-) 1(DEGREES)C and an LD 12:12 photoperiod. The CTM of D. ordi was significantly higher than that of all other species. The CTM of M. musculus was lower than the CTM of all other species. The CTM of P. leucopus was lower than that of R. norvegicus. There was no difference in CTM between M. unguiculatus and R. norvegicus.