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京都大学 / 新制・課程博士 / 博士(理学) / 甲第24875号 / 理博第4985号 / 新制||理||1712(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 MacIntosh Andrew, 教授 岡本 宗裕, 教授 明里 宏文 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Survival of females, nests, and ducklings strongly influence annual recruitment in North American ducks. Studies of cavity-nesting ducks using nest boxes, such as wood ducks (Aix sponsa), hooded merganser (Lophodytes cucullatus) and black-bellied whistling duck (Dendrocygna autumnalis) historically have investigated extrinsic factors, such as nest predation, and how it influenced nest success. For my study, I evaluated data from 1,403 monitored nest boxes collected from eight states, 2020–2022. I studied intrinsic characteristics related to reproduction, such as egg and clutch sizes, and eggshell strength in the 3 cavity-nesting ducks. Variables including clutch size, egg mass, parasitism, and onset of incubation influenced reproductive success of wood ducks. Latitude also influenced clutch size in wood ducks, where for every 14.3° increase in latitude, I found one more egg per clutch. Hooded mergansers had the strongest eggshells and eggshell composition varied across latitude in hooded merganser, but not in wood ducks.

The obligate stem parasite Cuscuta pentagona is able to take up host plant mRNA through a specialized organ known as the haustorium. Direct cell-to-cell symplastic connections between two different organisms are rare, and the translocation mechanisms and fate of these RNAs in the parasite is not understood. To characterize this phenomenon, mobile Arabidopsis and tomato mRNAs were identified from microarray and transcriptome sequencing projects and quantified in the host-parasite system. Mobile RNAs were quantified using real time (qRT)-PCR and were found to vary substantially in their rate of uptake and distribution in the parasite. Transcripts of tomato Gibberellic Acid Insensitive (SlGAI) and Cathepsin D Protease Inhibitor (SlPI) can be traced over 30-cm of parasite stem. SlPI was abundant in the C. pentagona stem, but the number of copies decreased substantially within the first eight hours post detachment. Additional studies of mobile RNAs from Arabidopsis, Translationally Controlled Tumor Protein (AtTCTP), Auxin Response Factor (AtARF) and a Salt-inducible Zinc Finger Protein (AtSZFP) supported the idea that mRNA molecules differ in their mechanisms of uptake and mobility between host and parasite. Known phloem-mobile RNAs (SlGAI and AtTCTP) have uptake patterns that differ from each other as well as from other RNAs that are not reported to be phloem mobile (SlPI and AtSZF1). The function of RNAs in plants extend beyond protein translation to include post transcriptional gene silencing or long distance signaling, and mobile RNA in C. pentagona systems offers novel insights into this aspect of plant biology. Studies of cell-to-cell trafficking of RNAs and other macromolecules would be facilitated by the ability to manipulate individual cells. To this end, work was initiated to explore alternative approaches to understanding single cell biology using laser-mediated approaches. Optoperforation, or the use of multiphoton processes to form quasi-free electron plasmas to initiate transient pore formation in plasma membranes, has been demonstrated, but not in cells of an intact plant. This work details a protocol for optoperforation of Arabidopsis epidermal cells to allow for uptake of external dye-labeled dextrans and retention for up to 72 hours, and has the potential for transformation and molecular tagging applications. / Ph. D.

2024 / Mnemiopsis leidyi, the sea walnut, is one of the most destructive invasive species in the world. The ctenophore has broad environmental tolerances, a high rate of zooplankton consumption, extensive regeneration capabilities, and extraordinary fecundity. While there is a substantial body of research on M. leidyi’s role as a predator of zooplankton and as prey to the ctenophore Beroe ovata, only a few studies have examined M. leidyi’s relationship with its parasite, the lined sea anemone, Edwardsiella lineata. Previous research has shown that E. lineata may be exerting top-down control on the ctenophore in areas where present along the Northwestern Atlantic; the parasite has not established a population in M. leidyi’s invasive range. While a handful of studies have examined the ecological relationship between host and parasite, all studies have taken place at the same site, Woods Hole, and some failed to report key parameters such as host size and parasite number. More detailed examinations of this relationship are necessary to understand the parasite’s potential for controlling host populations in both native and European waters and how this control may be affected under various abiotic conditions. In my dissertation I performed three studies exploring the ecological relationship between M. leidyi and E. lineata. First, I profiled the variation in infection frequency in populations in Massachusetts and Rhode Island and examined the relationship between host size, parasite load, and seasonality. My results show that in natural populations, infected ctenophores are larger than non-infected conspecifics. The pattern of infection was also highly variable across sites and time. Second, I tested the temperature and salinity tolerances of E. lineata larvae to determine if certain conditions, such as those found in the invasive range of M. leidyi are refuges for the host from parasitism. My data indicate that temperature and salinity conditions alone will not prevent E. lineata from establishing a population in Europe. However, developmental outcomes and survival are both reduced at lower salinities and higher temperatures. Finally, using a RAD-seq approach I profiled population connectivity between juvenile parasite and adult polyp populations of E. lineata in Massachusetts and Rhode Island. E. lineata populations were found to be panmictic like host M. leidyi, though some structuring appeared between parasite and polyp populations. While asexual reproduction was seen in polyp mats, none was found within hosts.These data help contribute to the wider body of research on the M. leidyi-E. lineata system and also provide data on sea anemone genetic structure, which is currently understudied. I suggest that future studies examine cues for asexual reproduction in both the parasite and host and profile infection frequency and genetic structure in populations further south. / 2027-02-10T00:00:00Z

Species interact and exploit one another for a number of reasons, including transportation, shelter or nutrition such as in parasitic relationships. Parasitism is an important aspect in life and is common in all taxonomic groups. Parasites are often host-specific and can be endoparasites or ectoparasites. The phylum Platyhelminthes includes the class Monogenea or monogenetic parasitic flukes. Monogeneans are mainly parasitic in fish but the family Polystomatidae, also commonly referred to as polystomes, are found on the skin and gills of the Australian lungfish, tadpole gills, kidneys and urinary bladders of frogs, gills and skin of salamanders, cloaca and phalodeum of caecileans, on the eye, in the nose, mouth or urinary bladder of freshwater turtles and on the eye of the hippopotamus. Polystomes have a cosmopolitan distribution, and are found on all hospitable continents. Polystome species were first discovered in the 1758. Between 1961 and 1980 French researchers focussed on Central and West Africa and described a large number of parasites. Polystome discovery has steadily decreased in the last 30 years, however despite this, new species are still being discovered annually. The list of currently known polystomes is most likely only a small portion of the species that exists. Wherever scientists searched for polystomes, new species were discovered. The current distribution of polystomes is not at all a true reflection of their global distribution but merely an indication of research effort. Monogenean flatworms exhibit many variations in the morphology of the intestinal tract. These parasites display two distinct diets, where one group mainly feeds on blood while the other mainly feeds on mucus and epithelial tissues. Thus the feeding habits and other factors such as the shape of the caeca, the presence/absence and number of medial and lateral diverticula as well as anastomosis may play a role in the morphology of the intestinal tract, which can be used as a classification tool to classify polystome species into specific genera. The three aims of the study were to:  Conduct a literature study to compile a species list and source of information on all valid polystome taxa.  Review the intestine shape of all polystomes and evaluate it as a taxonomic characteristic.  Conduct a species description of a new North American chelonian polystome belonging to the genus Polystomoides. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Species interact and exploit one another for a number of reasons, including transportation, shelter or nutrition such as in parasitic relationships. Parasitism is an important aspect in life and is common in all taxonomic groups. Parasites are often host-specific and can be endoparasites or ectoparasites. The phylum Platyhelminthes includes the class Monogenea or monogenetic parasitic flukes. Monogeneans are mainly parasitic in fish but the family Polystomatidae, also commonly referred to as polystomes, are found on the skin and gills of the Australian lungfish, tadpole gills, kidneys and urinary bladders of frogs, gills and skin of salamanders, cloaca and phalodeum of caecileans, on the eye, in the nose, mouth or urinary bladder of freshwater turtles and on the eye of the hippopotamus. Polystomes have a cosmopolitan distribution, and are found on all hospitable continents. Polystome species were first discovered in the 1758. Between 1961 and 1980 French researchers focussed on Central and West Africa and described a large number of parasites. Polystome discovery has steadily decreased in the last 30 years, however despite this, new species are still being discovered annually. The list of currently known polystomes is most likely only a small portion of the species that exists. Wherever scientists searched for polystomes, new species were discovered. The current distribution of polystomes is not at all a true reflection of their global distribution but merely an indication of research effort. Monogenean flatworms exhibit many variations in the morphology of the intestinal tract. These parasites display two distinct diets, where one group mainly feeds on blood while the other mainly feeds on mucus and epithelial tissues. Thus the feeding habits and other factors such as the shape of the caeca, the presence/absence and number of medial and lateral diverticula as well as anastomosis may play a role in the morphology of the intestinal tract, which can be used as a classification tool to classify polystome species into specific genera. The three aims of the study were to:  Conduct a literature study to compile a species list and source of information on all valid polystome taxa.  Review the intestine shape of all polystomes and evaluate it as a taxonomic characteristic.  Conduct a species description of a new North American chelonian polystome belonging to the genus Polystomoides. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

This thesis focuses on the trajectory of the biomedical concept of virulence from 1880 until the present. Following the concept across disciplinary boundaries, from a longue durée history perspective, it explores how virulence was shaped through two distinct, although sometimes overlapping, “styles of reasoning”. Located at the intersection of several distinct research domains in biology and medicine, the concept of virulence provides, in addition, a window into the complex and changing relations between evolutionary biology and the health sciences (broadly construed) over the past two centuries. Moving back and forth between field experiments and the laboratory, this work examines, through the lens of historical epistemology, the emergence of what I call the molecular and the ecological styles, and their respective conceptual practices. It focuses on the ways in which these styles operationalize the distinction between virulent or avirulent organisms in sometimes opposite sense: Whereas in the molecular (or endogenous) style the expression of virulence is explained by properties of internal structures of the infectious agent (e.g. polysaccharide capsule, virulence gene, or pathogenicity island), the concept of virulence in the ecological (or exogenous) style reflects, in contrast, either a lack of adaptation between two species (avirulence hypothesis) or the existence of one or more ecological compromises between, say, the mode of transmission of a pathogen and its host’s recovery rate (trade-off model). Both styles can be said to originate in the medical bacteriology of the late-nineteenth century, but while the former grew mostly out of the work of Louis Pasteur and Robert Koch in Europe, the latter was primarily shaped by Theobald Smith in the United States. Nearly a century later, the introduction of the category of emerging infectious disease within public health discourses in the mid-1990s facilitated a rapprochement between the two styles that had, so far, remained apart. Employing the 1918–1919 influenza pandemic as an example in which to illustrate the trajectory of the molecular and the ecological approaches, the diversity of explanatory schemes developed to account for the pandemic’s exceptional virulence points toward an unresolved, and yet productive, epistemic tension between the two styles, on the one hand, and the intrinsic polarity of the concept of virulence itself, on the other.

Understanding how floral traits covary with one another and with mating patterns is an important step in understanding how and why mating systems evolve. I examined the evolution of floral and mating system variation in Camissoniopsis cheiranthifolia (Onagraceae), a species that exhibits divergence in key floral traits expected to be associated with variation in the relative importance of outcrossing vs. self-fertilization. I combined geographic surveys of floral variation with genetic estimates of the proportion of seeds outcrossed (t) and confirmed that t covaried with corolla width and herkogamy in a predictable way both within and among populations. I then performed geographic surveys, manipulative experiments and genetic analyses to evaluate the potential role that; inbreeding depression (ID), interactions between flowers, pollinators and florivores, and reproductive assurance (RA) may have played in shaping and/or maintaining the geographic pattern of mating system variation in this species. The main selective factor maintaining outcrossing in large flowered (LF) populations appears to be ID, which was much stronger in LF compared to small flowered (SF) populations. These results are also consistent with purging of ID in SF populations. Increased selfing appeared to alleviate pollen limitation (PL) because it was associated with higher and less variable fruit set and reduced florivory by a microlepidopteran. However, evidence that florivores preferentially attacked larger flowers was equivocal. LF experienced stronger PL than SF populations suggesting that one condition for the evolution of selfing via RA is met in outcrossing populations. Floral emasculation experiments revealed that the timing of selfing also covaried with flower size among and within populations. SF self-pollinate before flowers open but LF do not, suggesting that selfing evolved in response to chronic outcross PL. Negative side effects of emasculation were detected which prevented a clear interpretation of the RA value of selfing. Given that much of what is known about RA comes from emasculation experiments, my results suggest that the assumptions of this approach, which are rarely verified, require more serious consideration. Taken together my results suggest that C. cheiranthifolia has evolved multiple stable mixed mating systems perhaps in response to selection for RA. / Thesis (Ph.D, Biology) -- Queen's University, 2012-12-30 14:13:46.366