Master of Science, The Ohio State University, 2006, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2024, Entomology

In order to survive, virtually all lifeforms on earth must be able to keep track of time, both throughout the day to predict light/dark cycles, and throughout the year to predict seasonal changes in temperature, rainfall and food availability. The former is accomplished through the circadian clock, which allows organisms to anticipate day and night, and thus synchronize an enormous variety of daily biological processes such as feeding, sleeping, mating, molting, and fending off pathogens. Predicting annual changes in environmental conditions is accomplished through the photoperiodic timekeeping system, which allows organisms to anticipate seasonal changes – such as the onset of winter or an approaching rainy season – that necessitate a long-term physiological response such as arrested development (e.g., overwintering diapause/hibernation or summer aestivation), migration, or gametogenesis. Early chronobiologists observed that many organisms tracked seasonal time by detecting the variations in daylength that occur because of the earth's axial tilt. Since this system inherently implies that seasonal timekeeping must be able to measure day/night cycles, it has long been hypothesized that the circadian clock integrates with and informs the seasonal clock. However, despite nearly a century of research, it remains unclear precisely how the circadian clock influences seasonal timekeeping in insects. A large body of the literature investigating circadian and photoperiodic timekeeping focuses on the rhythmic biological processes of insects. Insects represent a massively diverse group of organisms that inhabit virtually every terrestrial environment on earth. Consequently, they have also evolved an extremely diverse array of physiological and behavioral strategies that synchronize their biological processes to both the daily light:dark cycle and annual changes in temperature, humidity, and resource availability. Mosquitoes (Order Diptera, Family Culicidae) are highly dive (open full item for complete abstract)

Committee: Megan Meuti (Advisor); Bryan Carstens (Committee Member); Sarah Short (Committee Member); Andy Michel (Committee Member) Subjects: Entomology

PhD, University of Cincinnati, 2021, Arts and Sciences: Biological Sciences

Animals have evolved to overcome the consistent hardships encountered within their environment including biotic factors such as pathogens and predators as well as abiotic factors including temperature and rainfall. Diapause is one such program animals have developed to overcome adverse winter or summer conditions. Typically, reliable environmental cues trigger this alternative developmental pathway causing an extensive shift in both behavior and physiology. These changes permit diapausing organisms to over-winter or -summer successfully and restart spring populations more rapidly upon the return of favorable conditions. Many studies have investigated the environmental cues that initiate diapause and mechanisms underlying this alternative developmental pathway. To better understand diapause in the northern house mosquito, Culex pipiens, we utilized next generation sequencing to investigate the microbiota associated with diapause, in addition to other molecular and physiological techniques to better understand microbiota-diapause interactions and characterize temperature related immune response changes during diapause. Midgut microbial communities were identified with 16s rRNA amplicon sequencing within diapausing and nondiapausing mosquitoes. This revealed low diversity but high variability between individual samples suggesting that no specific microbiota was associated with diapause in C. pipiens. By comparing physiological metrics of mosquitoes with low bacterial load (LBL) to conventional and reconstituted mosquitoes, we were able to determine that the microbiota, as a whole, impacts diapause preparation. LBL mosquitoes accumulated less mass and lipid reserves and experienced lower survivorship, likely due to an inability to process sugars to accumulate lipid reserves, a critical component of diapause preparation. To better understand biotic and abiotic factors that influence C. pipiens diapause we investigated how the whole-body microbiota changed over the (open full item for complete abstract)

Committee: Joshua Benoit Ph.D (Committee Chair); Stephen Matter Ph.D (Committee Member); Zakee Sabree Ph.D (Committee Member); Stephanie Rollmann Ph.D (Committee Member); Trinity Hamilton (Committee Member) Subjects: Animals; Biology; Psychobiology

Master of Science, The Ohio State University, 2021, Entomology

Diapause, a period of arrested development that allows mosquitoes to survive inhospitable conditions, is triggered by short daylengths in temperate mosquitoes. Different populations of mosquitoes initiate diapause in response to a specific photoperiod, or daylength, resulting in population-specific differences in annual cycles of abundance. The photoperiod that causes approximately 50% of a population to initiate diapause is known as the critical photoperiod (CPP). In the Northern Hemisphere, northern populations of mosquitoes experience lower temperatures earlier in the year and must be triggered into diapause by longer daylengths than southern populations. CPP is genetically based, but also adapts over time responding to the population's environment. Therefore, CPP has been shown to lengthen 1 hour with an increase of 5 °N latitude or an increase of 122 m altitude, following Bioclimatic Law. While the positive correlation between CPP and latitude/altitude has been established in a few mosquito species, including Aedes albopictus, Ae. triseriatus, Ae. sirennensis and Wyeomyia smithii, we do not know when most other species initiate their seasonal responses. As several of these species transmit important diseases, characterizing the CPP of arthropod vectors could improve existing control by ensuring that surveillance efforts align with the vector's seasonally active period. Additionally, better understanding when mosquitoes and other vectors initiate diapause can reduce the frequency of chemical applications, thereby ameliorating the negative impacts to nontarget insects. Females of Culex pipiens, the primary vector of West Nile virus, enter an adult reproductive diapause. The methods by which Cx. pipiens measures daylength are still unknown. However, clock genes which provide information on the time of day, may also be responsible for the regulation of diapause. Previous studies have shown that the mRNA of several circadian clock genes continue to oscillate throu (open full item for complete abstract)

Committee: Megan Meuti PhD (Advisor); Mary Gardiner PhD (Committee Member); Peter Piermarini PhD (Committee Member) Subjects: Entomology

Doctor of Philosophy, The Ohio State University, 2017, Entomology

The northern house mosquito, Culex pipiens is the primary vector of West Nile virus and several other serious disease pathogens (e.g. St. Louis encephalitis and filariasis). Like other insects living in temperate regions, C. pipiens undergoes a dormant phase called diapause to cope with difficult environmental challenges during winter (e.g. extreme low temperatures and relative humidity). Aquaporins (AQPs) are a group of membrane-bound channel proteins that can transport water and/or other small molecules for many important physiological activities of insects responding to environmental changes. In addition to natural fluctuations to the environment, human activity (e.g. urbanization, land use management) is another factor that shapes mosquito communities. In Chapter 1, I first reviewed the current knowledge about mosquito diapause with the focus of molecular characteristics, and the knowledge of insect aquaporins from the aspects of 1) structure and classification, 2) functional studies, and 3) molecular expression and physiological roles. Then I reviewed the studies on the effects of urbanization on mosquito communities. In Chapter 2, I described the overall AQP mRNA expression patterns of C. pipiens under a variety of physiological and environmental conditions. In Chapter 3, I first discussed the role of renal excretory system in the theme of water conservation during diapause, then I characterized the molecular expressions of AQPs in the whole body and different tissues of C. pipiens during diapause to explain whether AQPs are responsible for the suppressed renal excretory capacity during diapause. In Chapter 4, I studied the effect of one of the most common urban greenspace management strategies (periodic mowing) on mosquito communities in the city of Cleveland, OH. Cleveland has a long manufacturing history and has lost over 50% of its population due to economic declines and recent foreclosure crises. The large numbers of vacant lands within the city are subje (open full item for complete abstract)

Committee: Peter Piermarini (Advisor); David Denlinger (Committee Member); Andy Michel (Committee Member); Luis Canas (Committee Member) Subjects: Entomology

Doctor of Philosophy, The Ohio State University, 1985, Graduate School

Committee: Not Provided (Other) Subjects: Biology

Doctor of Philosophy, The Ohio State University, 1983, Graduate School

Committee: Not Provided (Other) Subjects: Biology

Doctor of Philosophy, The Ohio State University, 1981, Graduate School

Committee: Not Provided (Other) Subjects: Biology

Doctor of Philosophy, The Ohio State University, 1981, Graduate School

Committee: Not Provided (Other) Subjects: Biology

PhD, University of Cincinnati, 2013, Medicine: Molecular and Developmental Biology

An effective bidirectional communication between an implantation-competent blastocyst and the receptive uterus is a prerequisite for mammalian reproduction. The blastocyst will implant only when this molecular cross-talk is established. Muscle segment homeobox gene (Msh) family members Msx1 and Msx2, which are two highly conserved genes critical for epithelial-mesenchymal interactions with overlapping function during development, also play crucial roles in embryo implantation. Msx1 is transiently expressed in the pregnant uterus during the window of receptivity from day 3 of pregnancy until the morning of day 4 with rapid downregulation with impending implantation. Uterine inactivation of Msx genes leads to infertility due to implantation failure, which correlates with altered uterine luminal epithelial cell polarity and affects E-cadherin/β-catenin complex formation through the transcriptional regulation of Wnt5a expression. Application of Wnt5a in vitro compromised blastocyst invasion and trophoblast outgrowth by cultured uterine epithelial cells.

Committee: Sudhansu K. Dey Ph.D. (Committee Chair); Stuart Handwerger M.D. (Committee Member); Sanjoy K. Das Ph.D. (Committee Member); Gurjit Hershey M.D. Ph.D. (Committee Member); Alan Jobe M.D. Ph.D. (Committee Member); Jeffrey Whitsett M.D. (Committee Member) Subjects: Developmental Biology

Doctor of Philosophy, The Ohio State University, 2009, Entomology

The northern house mosquito Culex pipiens L., a vector of arthropod-borne viruses, is capable of entering an overwintering dormancy known as diapause. Adult diapause in C. pipiens is regulated at environmental, hormonal, and molecular levels. In this thesis, select gene groups including cytoskeletal genes and genes encoding ribosomal proteins (rps) were cloned and their expression patterns and function related to diapause were examined. The gene in C. pipiens that encodes beta-tubulin, a major cytoskeletal gene, has high similarity with beta-tubulins from other insects. This gene was up-regulated in thoracic muscles (mostly flight muscles) of nondiapausing female mosquitoes but was down-regulated during diapause. Similarly, microtubule abundance was significantly lower in thoracic muscles of diapausing females than in thoracic muscles from nondiapausing females. Microtubule abundance also declined in midguts of nondiapausing females after low temperature exposure. However, in diapausing females, microtubule abundance was already low and remained at a low level even after low temperature exposure. These results showing lower expression of beta-tubulin and microtubule abundance in the thoracic muscles suggest a link to the reduced flight activity during diapause and in response to low temperature. Two ribosomal proteins located on a small ribosomal subunits, rpS3a and rpS2, are proposed to function in suppressing ovarian development during adult diapause in C. pipiens based on RNA interference (RNAi) results. RpS3a was continuously expressed in nondiapausing females but was less expressed for a brief period 7-10 days after adult eclosion in diapausing females. When RNAi was directed against rpS3a in nondiapausing females ovarian development was halted as it is in diapause. The effect persisted for approximately 10 days. Application of juvenile hormone III, an endocrine trigger known to terminate diapause, rescued the arrested ovarian development caused by dsrpS3a inj (open full item for complete abstract)

Committee: David Denlinger (Advisor); Susan Fisher (Committee Member); Glen Needham (Committee Member); Peter Reiser (Committee Member) Subjects: Entomology

Doctor of Philosophy, The Ohio State University, 2008, Entomology

Understanding the mechanisms used by insects to survive stress is critical for understanding adaptations to the environment and may suggest future tools for pest management. To this end, two very different flies from different parts of the world were examined to determine how they deal with environmental stressors in their habitat. The insects examined include the fruit fly Rhagoletis pomonella and the Antarctic midge, Belgica antarctica, two species that spend most of their immature period in the soil. The apple maggot, Rhagoletis pomonella, is a major pest of domesticated apples. It can spend most of the year (~11 months) in the soil in a deep diapause. During this time, the pupae are vulnerable to the low temperatures of winter as well as the warm temperatures of early summer. In late summer, adults emerge and oviposit into apples, where the larvae spend several weeks. The larvae then drop to the soil and pupariate. Infested apples were also placed in the field for a 24 hr period during August, and the heat shock proteins were monitored. During this time, the core temperature of the apples exceeded 40°C for at least 2 hrs per day. Hsp70 was mildly upregulated in the field at 9:30 am and upregulation was maximal at 5:30 pm. By 11 pm Hsp expression again declined and by 6 am the next day there was no signal. Hsp90 was again constitutively expressed during the entire day, but a strong upregulation was also noted at 5:30 pm. Hsp expression was also noted during diapause. Diapausing pupae were sampled at 30, 60, 90, 120, 150 and 250 days post pupariation. Hsp70 was expressed throughout diapause but was further upregulated at 120 d (deep diapause). Hsp90 was constitutively expressed during diapause. Larvae of the Antarctic midge, Belgica antarctica, spend nearly 11 months each year encased in a matrix of substrate and ice. During that time the larvae are exposed to the dehydrating conditions of being surrounded by ice, but they also experience numerous freeze and thaw (open full item for complete abstract)

Committee: David L. Denlinger PhD (Advisor); John W. Wenzel PhD (Committee Member); Celest Welty PhD (Committee Member) Subjects: Entomology

Doctor of Philosophy, The Ohio State University, 2008, Entomology

This dissertation focuses on patterns of protein synthesis that are linked to several different stress responses in insects. These include the overwintering dormancy response of insects, known as diapause; the response of insects to rapid drops in temperature, known as rapid cold hardening (RCH), and responses of an Antarctic insect to desiccation and rehydration.Proteomics, the comprehensive study of all proteins in an organism, has proven to be a powerful technique for studying changes in protein abundance during various stresses. However, only a few studies have used proteomics to examine diapause and stress responses in insects. The primary focus of this work is to identify proteins associated with diapause, low temperature and desiccation. The flesh fly, Sarcophaga crassipalpis, and the midge, Belgica antarctica, were used as model organisms. A proteomic analysis of pupal brains in S. crassipalpis revealed that heat shock proteins (Hsp) were among the most conspicuous brain proteins present in higher amounts during diapause. While the mRNAs encoding Hsps were previously known to be associated with diapause, other proteins identified during this study were not known to be linked to diapause, thus suggesting that the proteomic approach nicely supplements work done at the transcript level. A gene encoding neuropeptide like precursor 4 in S. crassipalpis showed close association with diapause, suggesting a potential role for this gene in initiating and maintaining diapause. Changes in brain proteins following pupal diapause termination in S. crassipalpis showed an increase in abundance of myo-inositol-1-phosphate synthase (Inos). The elevation of Inos at diapause termination is likely downstream of the physiological regulation that initiates development. During RCH, an increase in ATP synthase suggests that an elevation of ATP is an important component of this response, and a small Hsp increase suggests that at least one of the Hsps is actually mobilized during R (open full item for complete abstract)

Committee: David Denlinger PhD (Advisor); Donald Dean PhD (Committee Member); Glen Needham PhD (Committee Member) Subjects: Biology; Entomology

Doctor of Philosophy, The Ohio State University, 2005, Entomology

One of the primary avian vectors of West Nile virus in the northern United States, Culex pipiens (L.), enters an adult diapause in late summer and early fall in response to short daylength and low temperature. The mosquitoes first appear in overwintering sites such as caves, culverts, and unheated basements as early as August and remain there until spring when environmental conditions again become favorable for development. Only females enter diapause and most are inseminated prior to entering the hibernation site. In preparation for diapause, females increase their lipid reserves by feeding on sugar-rich sources such as nectar and rotting fruit. Although females programmed for diapause can be enticed to take a blood meal by being placed in close proximity to a host, it appears this rarely, if ever, happens in the field. Failure of diapausing females to take a blood meal is presumably the reason that so few of the overwintering females harbor West Nile virus. Many aspects of diapause in Cx. pipiens have been well documented. There is a good database that describes the physiological features of this diapause, its environmental regulators, and the hormonal control mechanism. What is currently lacking is an understanding of its molecular underpinning. In this study, suppressive subtractive hybridization (SSH) is used to identify genes that are differentially expressed during the adult diapause of Cx. pipiens. Expression patterns are confirmed by northern blot hybridization, and the regulated genes that have been identified are discussed in the context of their possible functional contributions to diapause.

Committee: David Denlinger (Advisor) Subjects: Biology, Entomology

Doctor of Philosophy (PhD), Ohio University, 2007, Biological Sciences (Arts and Sciences)

I studied how the expression, timing, and duration of embryonic diapause (ED), morphogenesis, and embryonic aestivation (EA) relate to variation in environmental conditions experienced by turtle embryos. ED and EA are putative mechanisms that increase embryonic survivorship. ED arrests development before main morphogenesis and is induced before the onset of adverse environmental conditions. EA prolongs incubation by depressing the metabolism of the embryo after completion of morphogenesis. I tested two hypotheses with regard to the environmental conditions that stimulate ED and EA based on climatic patterns. My first hypothesis suggested a single suitable developmental period (SDT; periods when soil moisture and temperature of nesting substrate are within the physiological tolerances of developing embryos) during the dry seasons, and my second hypothesis predicted two SDTs at the transition from the rainy and dry seasons. Incubation experiments using white-lipped mud turtle, Kinosternon leucostomum, embryos confirmed that temperature is an important factor in determining the duration of both ED and morphogenesis, and that morphogenesis occurs during the dry season SDT. Female size generally correlates positively with egg and offspring size. However, when embryos experience prolonged incubation periods, females may alter their reproductive investment strategies to offset potential additional embryonic energy expenditures. When accounting for female size, larger clutches had eggs with greater mass than smaller clutches; and egg size increased with female size. Thus in K. leucostomum the typical relationship between egg size and clutch size as it pertains to division of maternal resources per propagule is weakened by the embryo's ability to arrest development during extended incubation periods. Nearly 50% of all turtle taxa are undocumented as to the expression of ED. I used categorical data modeling to create probabilities for predicting ED expression. Results indicat (open full item for complete abstract)

Committee: Willem Roosenburg (Advisor) Subjects: Biology, Ecology

Master of Science, Miami University, 2007, Zoology

The ontogenetic development of cold-hardening associated with diapause was examined in feeding and wandering larval stages of the flesh fly, Sarcophaga crassipalpis. Cold tolerance was greatest for diapause-destined wandering larvae, as 62% of cold-shocked (-9 °C, 2 h) diapause-destined individuals progressed to adult development as compared to only 10% of wandering, non-diapause-destined larvae. The cell viability of Malpighian tubules and fat bodies of cold-shocked diapause-destined wandering larvae were significantly greater (91%, 90%) than in non-diapause-destined groups (64%, 75%). The diapause program influenced the composition of membrane fatty acids (FAs). The dominant unsaturated fatty acid, oleic acid, accounted for only 18% of the total phospholipid FA proportion in diapause-destined groups, down from 36% in non-diapause-destined larvae. This shift in oleic acid, coupled with increases in the principal saturated FA species in diapause-destined larvae, resulted in an index of unsaturation significantly lower (0.57) than in non-diapause-destined larvae (1.08).

Committee: Richard Lee (Advisor) Subjects: