Biological Sciences

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Research from the Department of Biological Sciences. The department website may be found at https://www.ndsu.edu/biology/

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Now showing 1 - 14 of 14

Development of the Stress Response in Fast (Coturnix Japonica) Versus Slow (Callipepla Gambelii) Growing Species
(North Dakota State University, 2012) Gastecki, Michelle Lynn
In this study, we evaluated the development of stress response in (1) two different species of quail, one species that is relatively fast-growing (Japanese quail, Coturnix japonica) and one that is relatively slow-growing (Gambel’s quail, Callipepla gambelii) and (2) two strains of a single species, the Japanese quail (wild-type and domesticated), that differ considerably in final size. Our data indicate that wild-type Japanese quail and Gambel’s quail have experienced trade-offs between growth and the stress response (e.g. Gambel’s quail have slower growth rates, but greater levels of CORT). However, the domesticated strain of Japanese quail used in this study seem to violate some predictions based on the life history theory (e.g. the domestic strain has faster growth rates and greater levels of CORT). The data in this study contribute to the understanding of differences in the stress response between species that exhibit different life history strategies.
Developmental Effects on Immunity: Hormonal and Proteinase Control
(North Dakota State University, 2016) Booth, Kimberly Katie
Insects are ubiquitous, diverse, and able to combat infections despite their lack of adaptive immunity. Insects have a robust innate immune system that is divided into two branches, cell-mediated and humoral. Activation of cell-mediated immune responses results in phagocytosis, nodule formation, and encapsulation by the insect’s immune cells, hemocytes. Activation of humoral immunity results in the production of anti-microbial peptides (AMPs) and phenoloxidase (PO). Insect immune responses can be plastic with development. However, research on how and why insect immunity changes with age as insects develop within a larval developmental stage (instar) is limited and contradictory. In my dissertation research, I answer two main questions: 1) how do immune responses vary within an instar and 2) what drives changes in immunity within an instar? My dissertation research showed that humoral immune responses are more robust at the beginning of the 5th and final instar in Manduca sexta (tobacco hornworm) compared to responses from animals later within that instar. Many changes occur within an instar that could affect immunity. For example, I found that protein expression of matrix metalloproteinase (MMP) in immune tissues of M. sexta decreases throughout the 5th instar. Though MMPs are involved in immune responses in other insects, MMP was not found to be immunostimulatory in M. sexta. Another important factor that changes within an instar is the level of juvenile hormone (JH). JH, a developmental hormone that prevents early molting, peaks early and decreases within an instar until molting. I determined that JH is necessary to survive an infection, control bacterial growth in hemolymph (insect blood), and mount an AMP activity immune response. My dissertation research has established that there is a development-immunity link, and that the naturally fluctuating levels of JH may mediate the effect of development on immunity.
Ecophysiological Implications of Spring Conditions on the Alfalfa Leafcutting Bee, Megachile rotundata
(North Dakota State University, 2017) Bennett, Meghan Marie
Spring conditions stimulate development of many plants and animals after a period of winter dormancy. Climate change is predicted to cause earlier spring thaws, increasing temperature variability, and more frequent cold snaps. These conditions cause two problems for organisms. First, environmental cues may mislead organisms developing under these scenarios if temperature and photoperiod cues give conflicting information. Second, organisms outside of their overwintering stages can be less tolerant of cold exposure and may be at risk of injury or death. Little is known about the consequences of these conditions on bee species. Therefore, I examined these scenarios in a solitary bee species, Megachile rotundata. I hypothesized they would be sensitive to temperature changes to regulate spring emergence because of their cavity nesting life history where photoperiod cues likely buffered. I found light is buffered by the brood cell by approximately 80% and emergence can be synchronized by photoperiod. Furthermore, I demonstrated that M. rotundata may be more sensitive to temperature cues compared to photoperiod cues in regulating emergence. To understand how spring cold snaps during development affect adult bees, I comprehensively assayed M. rotundata cold tolerance. I discovered that cold exposure during development resulted in numerous sub-lethal effects in adult bees such as a decrease in flight performance and longevity. Furthermore, developmental cold stress affected adult thermal performance, such as chill coma recovery. Cold tolerance varies across development and the post-diapause quiescent stage was more tolerant to cold than pupal or emergence ready stages. Temperature fluctuations of spring may affect the timing of emergence but also the health of adult bees if they experienced a cold snap during development.
Effects of Phylogenetic Tree Style on Student Comprehension
(North Dakota State University, 2017) Dees, Jonathan Andrew
Phylogenetic trees are powerful tools of evolutionary biology that have become prominent across the life sciences. Consequently, learning to interpret and reason from phylogenetic trees is now an essential component of biology education. However, students often struggle to understand these diagrams, even after explicit instruction. One factor that has been observed to affect student understanding of phylogenetic trees is style (i.e., diagonal or bracket). The goal of this dissertation research was to systematically explore effects of style on student interpretations and construction of phylogenetic trees in the context of an introductory biology course. Before instruction, students were significantly more accurate with bracket phylogenetic trees for a variety of interpretation and construction tasks. Explicit instruction that balanced the use of diagonal and bracket phylogenetic trees mitigated some, but not all, style effects. After instruction, students were significantly more accurate for interpretation tasks involving taxa relatedness and construction exercises when using the bracket style. Based on this dissertation research and prior studies on style effects, I advocate for introductory biology instructors to use only the bracket style. Future research should examine causes of style effects and variables other than style to inform the development of research-based instruction that best supports student understanding of phylogenetic trees.
Environmental Components of Phenotypic Variation Dietary and Trans-Generational Effects on Behavior
(North Dakota State University, 2017) Garrison, Courtney
Phenotypic variation, or the total variation in a trait, and its components are of great importance in the fields of evolutionary and behavioral ecology. Phenotypic variation can be broken down into both environmental and genetic influences on that particular trait. However, due to an increasing trend of quantitative genetics in behavioral studies, researchers have begun to consider lesser studied components of phenotypic variation in addition to the commonly studied direct environmental and genetic influences. Some of these lesser studied components include maternal and paternal effects, or the effect that parental phenotype has on their offspring’s phenotype. In Chapter 1, I examine the impacts of direct environmental manipulation on cricket song production. For Chapter 2 however, instead of examining the direct environmental influence at the individual level, I examine, through meta-analysis, how the indirect environmental influences that occur at both the maternal and paternal level impact offspring phenotype across taxa.
The Evolution and Development of a Novel Trait in Sepsidae
(North Dakota State University, 2016) Melicher, Dacotah
Evolutionary novelty, the appearance of new traits with no existing homology, is central to the adaptive radiation of new species. Novel traits inform our understanding of development and how developmental mechanisms can generate novelties. Sepsid flies (Diptera: Sepsidae) have a sexually dimorphic, jointed appendage used for courtship and mating. The appendage develops from the fourth abdominal histoblast nest rather than an imaginal disc. Histoblast nests in other species produce the adult epidermis and lack three-dimensional organization. The sepsid system is an opportunity to investigate the evolutionary history of a novel trait and the developmental mechanisms that pattern epidermal tissue into a complex structure. The appendage has a complex history of gain, loss, and recovery over evolutionary time. Appendage morphology is highly variable between species and does not correlate to body size. I collected larval epidermal tissue from 16 species across Sepsidae and one outgroup to trace the evolutionary history of gain, secondary loss, and recovery. I characterized histoblast nests in all segments and sexes, determining the nest size, number, and size of cells. The appendage-producing nest is sexually dimorphic in species after primary gain. Loss of the appendage shows a return to ancestral state while regain shows an increase in nest size in both sexes. The loss of sex dimorphism may indicate that mechanisms involved in specification may be active in females while genes involved in patterning are not activated during pupation. I assembled and annotated a reference transcriptome for the sepsid Themira biloba at using a custom bioinformatic pipeline that uses a merged assembly approach to maximize quality. This pipeline demonstrated an improvement over other methodologies using multiple published metrics for determining quality and completion. This pipeline also demonstrates how cloud computing architecture can complete bioinformatic tasks quickly and at low cost. I used the T. biloba transcriptome to identify differentially expressed genes involved in appendage patterning during pupation. I sequenced the appendage producing fourth male larval segment and the third male and fourth female segments. Many of the differentially expressed transcripts are involved in cell signaling, epidermal growth, and transcripts involved morphological development in other species.
Evolution of the Growth Hormone Receptor: Insights Into the Molecular Basis of the Physiologically Pleiotropic Nature of the Growth Hormone Receptor
(North Dakota State University, 2014) Ellens, Elizabeth Rose
One of the oldest, extant, lineages of vertebrates, the sea lamprey, was used to clarify the evolutionary origin and divergence of the growth hormone receptor (GHR) family. A single, full-length, cDNA, and a second, partial, cDNA were identified and shown to encode proteins that share amino acid identity with GHRs and prolactin receptors (PRLR s) previously identified. The complexity of the dynamic signaling system, with special emphasis on this system in fish and in the context of the evolution of this system, is discussed in the first chapter. The second chapter integrates the new insights gained by these studies. Included is a newly proposed phylogenetic analysis and revised nomenclature-system for vertebrate GHRs that better represents the evolutionary history of the receptor family. The molecular evolution of the receptors is, furthermore, highlighted as the backdrop for the continued discussion regarding how the GH-family of hormones exhibit such coordinated and pleiotropic actions.
Examination of Age at Death Methods and the Effects on Estimation Accuracy when Applied to Computed Tomography Scans and Virtual Models of Mummies
(North Dakota State University, 2015) Schanandore, James
Three-dimensional (3D) medical imaging provides a method to non-invasively examine the sub-surface structures of a mummified body, particularly the skeleton. The unique nature of both natural and anthropogenic mummification processes causes inconsistencies for estimating accurate age at death for a particular mummy or group of mummies. These inaccuracies are compounded when age at death methods are used in relation to 3D virtual models. There is a need for the examination of methods being used in mummy case studies and how they are being applied to the 3D virtual models. My research encompassed three studies that addressed the relationship of and the variability when estimating age at death of mummies using radiological imaging. In one study, 146 published case studies were examined for which methods were used to estimate age at death. This study found that articles often provided an assessment of age, but many failed to specify the methods used to calculate the estimated age, and if specified methods were limited to certain areas of the body. In a second study, a cohort of age at death methods was applied to a sample of 17 adult mummies and it was determined that some methods do not transpose well and consequently provided inaccurate age at death estimations when applied to 3D virtual models. Modifications to traditional osteological approaches for age estimation were sometimes necessary due to the presence of soft tissue and post-mortem changes to the body. This study proposes that more methods are needed that utilize the tools available for radiological images in order to limit the variability of transposing a traditional age at death method to virtual 3D models. In the third study, the rim height of the auricular surface was measured using computed tomography scans of 97 living or recently deceased individuals’. These measurements targeted areas around the edge of the surface, for example the height of the apex above the surface. The rim height above the surface produced models that can accurately predict age at death.
From Alcelaphus to Zapus: Conservation of Modern Mammalian Populations
(North Dakota State University, 2015) Preston, Kathryn Anne
Conservation priorities are increasingly important in the face of modern human activities. Anthropogenic activities such as deforestation, pollution, and climate change have negative impacts on all vertebrates. In chapter 1, I examine whether there are relationships among density dependence, population size variability, and extinction risk in mammals to see whether these parameters are indicative of population health. Also included were analyses of how body mass and age to maturity affect those three measures. On a smaller, more local scale, I asked questions regarding biodiversity of small mammals in a highly fragmented environment, the tallgrass prairie. In chapter 2, I examined how cattle grazing impacts small mammal biodiversity in the Sheyenne National Grassland on a short term, season-long scale. By understanding the interaction of large herbivores, vegetation height, and small mammals, appropriate measures can be taken to conserve this rare habitat properly, without sacrificing biodiversity.
Growth Hormone Mediated Regulation of Osmoregulation in Euryhaline Teleosts
(North Dakota State University, 2014) Martin, Lincoln
Within the multitude of fish species that exist on our planet, there are a certain number that possess the unique ability to live in both freshwater (FW) and seawater (SW) environments. This ability, known as euryhalinity, is limited to a relatively small number of species, thus making it a prime target for scientific research into osmoregulation, due to the uniqueness of this ability. It has been shown previously that growth hormone (GH) plays an important role in regulating this ability, and in this work, Atlantic salmon (Salmo salar) and Rainbow trout (Oncorhynchus mykiss) were used as models to examine the expression of specific osmoregulatory genes in response to SW transfer and GH exposure, and to examine the signaling mechanisms used by GH to facilitate any changes. We found that GH utilizes specific cell signaling pathways to facilitate the transition between FW and SW in both Rainbow trout and Atlantic salmon.
Low Temperature Stress in the Alfalfa Leafcutting Bee, Megachile Rotundata
(North Dakota State University, 2017) Torson, Alex S.
Dramatic changes in ambient temperature can have a significant impact on insect physiology throughout development. The accumulations of the deleterious physiological effects throughout low temperature exposure are collectively known as chill injury. The mechanisms underpinning the downstream physiological consequences of chill injury such as oxidative stress, perturbations in ion homeostasis, and changes in metabolism have yet to be elucidated. Brief, daily pulses of increased temperatures have been shown to repair and/or protect against the continued accumulation of chill injury, leading to an increase in survival across several insect taxa. Until recently, no transcriptomic-level assessments of gene expression during low temperature stress had been conducted. In this document I present a comparison of low-temperature stress response mechanisms across life stages in the alfalfa leafcutting bee, Megachile rotundata. RNA-seq, qPCR and oxidative stress assays were used to determine the physiological effects of low temperature exposure on two life stages: one adapted for low-temperature exposure and one that is not. Differential expression analysis revealed distinct gene expression profiles between life stages. The lack of overlap in expression profiles suggests different mechanisms are driving the response. Furthermore, an overlap in the functional classes of differentially expressed transcripts suggest that the response may be physiologically robust, even though the response is variable at the level of gene expression. Gene expression suggests oxidative stress may be a critical component in chill injury response and recovery. Antioxidant activity and lipid peroxidation, a common proxy for oxidative stress, were assessed in both life stages. M. rotundata’s ability to cope with an induced oxidative stress did not vary between treatments in either life stage. Furthermore, a lack of statistical differences between treatments in lipid peroxidative do not support the hypothesis that the benefits of fluctuating temperatures are, in part, due to reduction in oxidative stress.
On the Origin of Modern Horse Breeds from Four Distinct Subspecies of Equus Caballus
(North Dakota State University, 2016) Brady, Margaret Turkish
Although the evolution and domestication of the horse has been extensively studied, many mysteries remain. No other animal has been as influential on the development of human societies and cultures as the horse. Horses have been used for milk, meat transportation, riding, plowing, transportation of goods, and recreation. Over the course of the domestication of the horse, specific traits were selected for or against depending on the intended use of the animal. A variety of types of horses appeared in different regions of the world and it has been theorized that several indigenous subspecies of wild horses were used to create the modern domestic breeds that we know today. This paper provides evidence that four subspecies are the forerunners to today’s horse.
Peripheral Hormone Interactions with the Growth Hormone-Insulin-Like Growth Factor (GH-IGF) System in Rainbow Trout
(North Dakota State University, 2019) Dickey, Lindsey Ann
The growth of vertebrates is primarily regulated by the growth hormone-insulin-like growth factor (GH-IGF) system, but not in isolation. The central question of this dissertation was how do other hormones peripheral to the GH-IGF system interact with the system, including feedbacks by GH and IGF themselves on various tissues in rainbow trout (Oncorhynchus mykiss)? The representative hormones selected were thyroxine, cortisol, and the sex steroids testosterone and estrogen, along with GH and IGF. These hormones were chosen because they are known to affect overall growth and development during specific life events, but exactly what target genes and what mechanisms are involved are only at the early stages of being delineated in fish. Liver and gill tissues were selected as representative tissues to assess the in vitro effects on growth-related genes of the GH-IGF system. A total of more than thirty experiments were conducted, including time- and concentration-response, inhibitory studies, hormone combination studies, and radio-receptor binding assays. Hormones were applied to whole tissue cultures and real-time quantitative-PCR was used to measure hormonal effects on GHR, IGF, and IGFR1 genes. Microsomal preparations were treated with selected hormones and radio-labeled GH or IGF. A gamma counter was used to measure receptor-ligand activity. GH and IGF were found to possess autocrine and/or paracrine actions in self-regulating target growth genes. Thyroxine had no direct effects on targeted growth genes but may interact with other molecules or hormones to elicit its effects on growth and development. Cortisol directly influenced target growth genes in a tissue-specific and isoform-specific manner. Finally, sex steroids differentially regulated the growth genes: estradiol inhibited growth genes while testosterone directly stimulated growth genes. These findings contribute to understanding how hormones peripheral to the GH-IGF system interact with the growth system.
Physiological Mechanisms Underpinning Growth and Aging in Wild Birds
(North Dakota State University, 2019) Sirman, Aubrey Erin
Life-history trade-offs have been well-documented within the literature through correlational and experimental studies. However, the physiological mechanisms underlying these trade-offs are less understood. Currently, there is great interest in shared mechanisms, specifically endocrine mechanisms, that might underlie the variation in life-history traits. Insulin-like growth factor-1 (IGF-1) may be one shared mechanism that is particularly important. IGF-1 is a metabolic hormone that is part of a highly conserved insulin-signaling pathway known to influence multiple life-history traits including growth and longevity across taxa, however, little is known about these trade-offs outside of laboratory populations. This dissertation focuses on the role of IGF-1 as a hormonal mechanism underlying the life-history trade-off between growth and aging in wild birds. While the causes of aging are not fully understood, telomere dynamics (length and change in length) are a potentially important mechanism underlying lifespan. To investigate the role of IGF-1 as a hormonal mechanism underlying the life-history trade-off between growth and aging in Franklin’s gulls (Leucophaeus pipixcan) and house sparrows (Passer domesticus). In Franklin’s gulls, dietary restriction reduced growth rate and IGF-1 levels but did not impact telomere dynamics. However, there was a significant negative correlation between IGF-1 levels and telomere length at the end of the post-natal growth period. In house sparrows, we found that nestling growth rates varied with respect to year, but IGF-1 levels did not. Telomere dynamics were not related to growth rates or IGF-1 levels, suggesting that during post-natal growth nestlings may be able to mitigate or even delay costs to later life stages. Finally, when exogenous IGF-1 was administered to house sparrow nestlings during the post-natal growth period, nestling growth was impacted but only in some years. Exogenous IGF-1 increased growth and final mass in 2016 and final mass in 2018. There was a trend suggesting experimental birds had shorter telomeres in 2016. Similarly, in 2018, experimental birds had significantly shorter telomeres than control birds. These effects were not observed in 2017, suggesting that trade-offs between growth an aging might only be visible under certain environmental conditions, which may vary with respect to year.

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