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Full-Text Articles in Life Sciences
Mechanisms Underlying Freeze Tolerance In The Spring Field Cricket, Gryllus Veletis, Jantina Toxopeus
Mechanisms Underlying Freeze Tolerance In The Spring Field Cricket, Gryllus Veletis, Jantina Toxopeus
Electronic Thesis and Dissertation Repository
Freeze tolerance has evolved repeatedly across insects, facilitating survival in low temperature environments. Internal ice formation poses several challenges, but the mechanisms that mitigate these challenges in freeze-tolerant insects are not well understood. To better understand how insects survive freezing, I describe a novel laboratory model, the spring field cricket Gryllus veletis (Orthoptera: Gryllidae). Following acclimation to six weeks of decreasing temperature and photoperiod (mimicking autumn), G. veletis juveniles becomes moderately freeze-tolerant, surviving freezing at -8 °C for up to one week, and surviving temperatures as low as -12 °C. Acclimation is associated with increased control of the temperature and …
Mechanisms Underlying Variation In Insect Chill Tolerance: The Role Of Ion And Water Transport, Lauren E. Des Marteaux
Mechanisms Underlying Variation In Insect Chill Tolerance: The Role Of Ion And Water Transport, Lauren E. Des Marteaux
Electronic Thesis and Dissertation Repository
Water and ion homeostasis has emerged as an important factor limiting chill-susceptible insects at low temperatures; loss of this homeostasis in the cold likely contributes to chronic chilling injury, and reestablishment of homeostasis is required for recovery from chilling. Both plastic and interspecific variation in cold tolerance correlates with enhanced defense of water and ion homeostasis during cold exposure, however the mechanisms are poorly understood. Using Gryllus crickets, I generated and tested hypotheses about the mechanisms underlying this variation in transport function. I first related interspecific variation in cold tolerance to water and ion balance in early chill coma. A …
Freeze Tolerance In The Spring Field Cricket, Gryllus Veletis, Alexander H. Mckinnon
Freeze Tolerance In The Spring Field Cricket, Gryllus Veletis, Alexander H. Mckinnon
Electronic Thesis and Dissertation Repository
Many insects are able to survive internal ice formation. However, the mechanisms underlying freeze tolerance are not well-understood, perhaps because of a lack of suitable model organisms. I found that the spring field cricket, Gryllus veletis, seasonally acquires freeze tolerance in the fall when kept outside in London, Ontario. Moreover, individuals acquired freeze tolerance in the laboratory in response to a simulated fall thermophotoperiod. Lab-acclimated G. veletis freeze at -6.1 ± 0.7 ºC and the acquisition of freeze tolerance is accompanied by the accumulation of proline and trehalose. Crickets survived temperatures as low as -12 ºC (1.5 h), and …
Low Temperature Tolerance Of Adult Drosophila Suzukii (Diptera: Drosophilidae), Ruth Jakobs
Low Temperature Tolerance Of Adult Drosophila Suzukii (Diptera: Drosophilidae), Ruth Jakobs
Electronic Thesis and Dissertation Repository
The crop pest Drosophila suzukii, native to Southeast Asia, has been found in Ontario since 2010. This raises concern with respect to it establishing permanent populations, however, little is known about its cold tolerance. I investigated the low-temperature tolerance, including phenotypic plasticity, of D. suzukii. While acclimation increased cold tolerance, there was no evidence of short-term cold-hardening. Chill coma occurs at -1.2 °C, which will limit winter activity. Cold shock decreased the reproductive output of females, but this negative effect may be mitigated by re-mating. Drosophila suzukii is chill-susceptible and 80 % of the flies die after exposure …
Cold-Activation Of The Drosophila Melanogaster Immune System, Golnaz Salehipourshirazi
Cold-Activation Of The Drosophila Melanogaster Immune System, Golnaz Salehipourshirazi
Electronic Thesis and Dissertation Repository
Evidence of immune response enhancement after cold exposure suggests that cold activates the insect immune system. I investigated whether the immune response of Drosophila melanogaster is activated by cold exposure in the absence of pathogens. To explore if different kinds of cold affect the immune response differently, I included acute and chronic cold exposure. I cold-exposed flies, and then examined up-regulation of immune-related genes. In addition, I measured hemocyte concentration, phenoloxidase activity, and woundinduced melanization. Acute cold exposure increased hemocyte concentration and woundinduced melanization. Chronic cold did not change hemocyte concentration, phenoloxidase activity or melanization in flies. Acute and chronic …
The Sub-Lethal Effects Of Repeated Cold Exposure In Insects, Katie Elizabeth Marshall
The Sub-Lethal Effects Of Repeated Cold Exposure In Insects, Katie Elizabeth Marshall
Electronic Thesis and Dissertation Repository
While insect cold tolerance has been well studied, the vast majority of work has focused on the effects of a single cold exposure. However, many abiotic environmental stresses, including temperature, fluctuate within an organism's lifespan. In this thesis I address two major questions. First, does frequency of cold exposure impose additional stress on insects? Second, how does this stress translate to performance and fitness? I first summarize the literature on the effects of repeated cold exposure in insects, critically examining experimental designs. I then address my questions experimentally using four insect species with contrasting life histories and responses to cold …
Cold Tolerance Of Each Life Stage Of The Sub-Alpine Willow Leaf Beetle, Chrysomela Aeneicollis, Evelyn C. Boychuk
Cold Tolerance Of Each Life Stage Of The Sub-Alpine Willow Leaf Beetle, Chrysomela Aeneicollis, Evelyn C. Boychuk
Electronic Thesis and Dissertation Repository
To understand the potential effects of climate change on the sub-alpine willow leaf beetle, the cold tolerance strategy and mechanisms involved in cold tolerance were investigated for all life stages. Microhabitat choice and microclimate temperatures within each microhabitat were related to median lethal temperature for each life stage. Summer active and quiescent adults are freeze tolerant, eggs and pupae are freeze avoidant and all larval stages are chill susceptible. Quiescent adults accumulated the highest concentration of glycerol (~24 mM) and haemolymph osmolality (875 mOsm). Haemolymph from pupae had angular crystals suggestive of antifreeze agent activity, but this was absent in …