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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Fuels for Winter: The Role of Proline in Overwintering Bumblebee Queens (Bombus impatiens)

Rondot, Ariane 10 June 2020 (has links)
The common eastern bumblebee queens (Bombus impatiens) endure cold winter months by entering a diapausal state post-fertilization. During this overwintering period, these animals use stored energy reserves while maintaining a low metabolic rate. Bumblebees are thought to use primarily lipids to fuel this critical overwintering period, despite the fact that bee mitochondria do not appear equipped to break down this metabolic fuel. For some insects, lipids stored in the fat body can be converted to the amino acid proline, and this metabolic fuel has recently been discovered to be readily oxidized by bumblebee workers. My research, therefore, investigates the role of proline during overwintering in bumblebee queens. Using cellular respirometry, I determined the metabolic capacity of the muscle cells of queens to use various fuels, and if this capacity changes throughout overwintering. Surprisingly, the tested queens showed a much lower potential to oxidize proline than workers, and their capacity did not change during a four-month overwintering period. The metabolic properties of muscle tissue were further characterized using metabolic enzymes activity profile. These results further demonstrate the low potential for proline metabolism and the limitations of bumblebee queens’ capacity to oxidize lipids. Body composition was measured to determine how the various energy stores (lipid, glycogen, protein) change during overwintering; however, no decrease in concentration was observed. Overall, this work clarifies the constraints of B. impatiens metabolism during overwintering.
2

The feeding and fat dynamics of resident juvenile Atlantic salmon (Salmo salar L.) during winter

Bull, Colin D. January 1996 (has links)
This thesis investigated the relationships between the feeding behaviour and use of stored fat in overwintering Atlantic salmon parr remaining destined to remain resident in freshwater the following year. Experiments investigated the responses to periods of food shortage at different times of the year to assess the influence of season. Investigations were carried out to examine how feeding motivation and fat storage were influenced by changes in those environmental cues that indicate the change of season. The effect of the normal winter behavioural pattern upon feeding and fat was also investigated.
3

Physiological and molecular adaptations during diapause development and overwintering in a heteropteran bug, Pyrrhocoris apterus / Physiological and molecular adaptations during diapause development and overwintering in a heteropteran bug, Pyrrhocoris apterus

BOROVANSKÁ, Michaela January 2009 (has links)
In this thesis I present complex experimental data on the physiological and molecular adaptations during diapause development and overwintering in a linden bug, Pyrrhocoris apterus (Heteroptera, Pyrrhocoridae). I focus on adjustments of the enzymatic complement, which is involved in the biosynthesis of cryoprotectants, and heat shock proteins, which are expressed in response to temperature stress.
4

Increasing the overwintering survival of container-grown perennials

Harris, William Kevin 12 December 2011 (has links)
Container grown perennials are a popular product offered by nurseries and greenhouses and included in their production but little research has been reported on proper overwintering techniques for herbaceous perennials and ornamental grasses. In the first experiment rooted liners of Pennisetum alopecuroides, Pennisetum â Hamelnâ and Pennisetum â Little Bunny,â were potted. Treatments included, utilizing two overwintering covers, two fertilizer rates (low or high) and two substrate moisture contents (wet or dry). Covering with either a double layer of Dewitt N-Sulateâ ¢ insulation fabric or a double layer of Dewitt N-Sulateâ ¢ insulation fabric and a single sheet of 4 mil white polyethylene plastic on top of the insulation fabric, wet substrate treatments, low fertility rates and combinations of both, improved survival and vigor for all three tested Pennisetum species and cultivars. In the second experiment, rooted liners of P. alopecuroides, P. â Hamelnâ and P. â Little Bunny,â were potted. Treatments included, two transplanting times (young or old), two fertilizer rates (low or high) and two substrate moisture contents (wet or dry) at the UHC and Poplar Ridge Nursery (Montross, VA) (PR). Vigor was improved for P. alopecuroides (at PR) and P. â Little Bunnyâ (at both locations) with the young transplanting time. In the third experiment, older plant material of P. alopecuroides, P. â Hamelnâ and P. â Little Bunny,â were subjected to fertility treatments of no additional fertilizer or top-dressed at a low, medium or high rate . A high fertility rate reduced survival and vigor for P. â Little Bunny.â In the fourth experiment rooted liners of Echinacea purpurea â Hot Papaya,â Echinacea purpurea â Milkshake,â Gaillardia x grandiflora â Gallo Peach,â Heuchera x villosa â Pistache,â Heuchera x villosa â Brownies,â P. alopecuroides, P. â Cassian,â P. â Hamelnâ and P. â Little Bunny,â were potted and overwintered at the UHC or Poplar Ridge Nursery (Montross, VA) (PR) or Riverbend Nursery, Inc. (Riner, VA) (RB). Treatments included, utilizing two overwintering covers, two fertilizer rates (low or high) and two substrate moisture contents (wet or dry). Vigor at the UHC, was reduced with the high fertility rate for E. â Hot Papayaâ and H. â Brownies.â A double layer of Dewitt N-Sulateâ ¢ insulation fabric and white polyethylene plastic on top of the cover, in combination with the wet substrate moisture treatment improved vigor of E. â Hot Papaya.â A double layer of Dewitt N-Sulateâ ¢ insulation fabric in combination with the wet substrate moisture content and the high fertility rate reduced P. â Cassianâ vigor. No overwintering cover reduced P. â Hamelnâ vigor. No overwintering cover and the high fertility rate reduced P. â Little Bunnyâ vigor. Vigor at PR was improved with the high fertility rate for E. â Milkshake,â G. â Gallo Peachâ and H. â Brownies.â At RB, a double layer of Dewitt N-Sulateâ ¢ insulation fabric in combination with the low fertility treatment and no cover in combination with the high fertility treatment reduced vigor for E. â Milkshakeâ and P. â Little Bunny,â respectively. No cover in combination with the wet substrate moisture treatment reduced vigor for G.â Gallo Peach.â / Master of Science
5

The Effect of Protective Materials on the Overwintering of Hardy Annuals, Candytuft and Stocks

Burningham, Melvin S. 01 May 1966 (has links)
Many hardy annual flowers will live through the winter if there is sufficient snow protection. Since snow cover is not consistent from year to year it has been suggested that hardy annuals planted in late summer and provided with some kind of protection before severe freezing begins will live through the winter successfully. Not only would this enable plants to bloom four to six weeks earlier, but would also enable gardeners to utilize flowers not commonly grown in northern Utah.
6

Studies on the vector ecology of the American dog tick, Dermacentor variabilis, (Say) (Acari: Ixodidae) in Manitoba, Canada

Yunik, Matthew 02 September 2014 (has links)
The American dog tick, Dermacentor variabilis, is an obligate blood feeding ectoparasite. This tick is a known vector of pathogens that affect the health of wildlife, humans, and livestock and is abundant in Manitoba. The etiological agent of bovine anaplasmosis, Anaplasma marginale, along with members of the spotted fever group rickettsiae are bacteria that are transmitted by this tick. I examined the distribution of these bacteria in Manitoba’s tick population using molecular techniques. During the eradication of an outbreak of bovine anaplasmosis in Manitoba, there was no evidence the bacterium had spilled over into the tick population. Rickettsia montanensis was detected with a mean prevalence of infection of 9.8% (range, 0.00 - 21.74% among localities) in 8 of 10 localities within the province. It was also determined that 19.9% (SE ±1.14) of adult questing ticks collected in one vector season overwintered through to the next spring.
7

Trait Correlation and Confirmation of QTLs for Rhizome Growth and Over-wintering in Sorghum

Washburn, Jacob 2012 August 1900 (has links)
A growing world population drives an ever-increasing need for food and energy. These challenges, along with depletion of water and fossil fuel resources, call for improvements in crop production systems and the cultivars used within them. Perennial cropping systems present an attractive solution to many of these problems. A greater understanding of the genetic control of over-wintering ability within crop species is one way to begin the process of making perennial cropping systems a possibility. In this study an F3:F4 family derived from a cross between Sorghum bicolor (L.) Moench and S. propinquum (Kunth) Hitchc. segregating for rhizome production was phenotyped in both field and greenhouse environments for traits relating to rhizomatousness and over-wintering. Several statistical models were created to correlate rhizome growth and over-wintering. A known rhizome quantitative trait locus (QTL) region was saturated with SSR markers and the QTL interval was reduced from previous estimates of about 16 Mb or 7 cM to 12 Mb or 2 cM, a 25% or 71% reduction in physical or linkage distance respectively. Two previously unidentified QTL regions associated with over-wintering were also identified. Our results also support the hypothesis that rhizome growth is important and possibly necessary for over-wintering in Sorghum.
8

Ecology of Veliidae and Mesoveliidae (Heteroptera: Gerromorpha)in Central Europe / Ecology of Veliidae and Mesoveliidae (Heteroptera: Gerromorpha)in Central Europe

DITRICH, Tomáš January 2010 (has links)
Ecology of Veliidae and Mesoveliidae (Hemiptera: Heteroptera: Gerromorpha) was studied in selected European species. The research of these non-gerrid semiaquatic bugs was especially focused on voltinism, overwintering with physiological consequences and wing polymorphism with dispersal pattern. Hypotheses based on data from field surveys were tested by laboratory, mesocosm and field experiments. New data on life history traits and their ecophysiological consequences are discussed in seven original research papers (four published journal papers, two submitted papers and one communication in conference proceedings), creating core of this thesis.
9

Ecophysiological study on the alternative life cycles of males in the Japanese common grass yellow Eurema mandarina / キタキチョウのオスの生活史二型に関する生理生態学的研究

Konagaya, Tatsuro 26 March 2018 (has links)
Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(理学) / 甲第20954号 / 理博第4406号 / 新制||理||1633(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)教授 沼田 英治, 准教授 森 哲, 教授 中川 尚史 / 学位規則第4条第1項該当
10

Overwintering Mechanisms of La Crosse Virus Vectors

Bova, Jacob Edward 05 December 2018 (has links)
The La Crosse virus (LACV) is an emerging pathogen in the Appalachian region of the United States. The virus maintains a complex natural cycle through horizontal transmission with sciurid rodents and Aedes mosquitoes in Virginia. Transovarial transmission also occurs in this host-parasite system and has evolved for the virus to persist through winter. The virus perpetuates in diapause induced embryos and infects naive rodents the following spring. As global temperatures rise, it is imperative we evaluate how the virus and its vectors overwinter. We conducted experiments to evaluate and determine the diapause induction, or prediapause stage, in Aedes japonicus japonicus, and the ecophysiology and low temperature biology of how LACV affects Aedes triseriatus and Aedes albopictus embryos at low temperatures. We found that the prediapause stage of Ae. j. japonicus is the maternal stage, the developing adult female that lays diapause eggs. This more closely resembles Ae. albopictus and not Ae. triseriatus. As measured in the field and laboratory, LACV has a clear negative effect on the ability of Ae. triseriatus and Ae. albopictus to survive the winter. There was no major effect of LACV infection on the ability of these two species to enter diapause or their critical photoperiods, but there was a significant negative effect of LACV infection on survivorship of embryos that were placed in their natural habitat and in their susceptibility to low temperatures. LACV infection had a more significant negative effect on Ae. albopictus than on Ae. triseriatus and suggests that Ae. albopictus is a subordinate vector relative to Ae. triseriatus in the maintenance of the virus over the winter season. Our findings highlight the need for the increased surveillance of LACV as temperatures continue to rise due to climate change. / PHD

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