Matching Items (23)

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More oxygen during development enhanced flight performance but not thermal tolerance of Drosophila melanogaster

Description

High temperatures can stress animals by raising the oxygen demand above the oxygen supply. Consequently, animals under hypoxia could be more sensitive to heating than those exposed to normoxia. Although

High temperatures can stress animals by raising the oxygen demand above the oxygen supply. Consequently, animals under hypoxia could be more sensitive to heating than those exposed to normoxia. Although support for this model has been limited to aquatic animals, oxygen supply might limit the heat tolerance of terrestrial animals during energetically demanding activities. We evaluated this model by studying the flight performance and heat tolerance of flies (Drosophila melanogaster) acclimated and tested at different concentrations of oxygen (12%, 21%, and 31%). We expected that flies raised at hypoxia would develop into adults that were more likely to fly under hypoxia than would flies raised at normoxia or hyperoxia. We also expected flies to benefit from greater oxygen supply during testing. These effects should have been most pronounced at high temperatures, which impair locomotor performance. Contrary to our expectations, we found little evidence that flies raised at hypoxia flew better when tested at hypoxia or tolerated extreme heat better than did flies raised at normoxia or hyperoxia. Instead, flies raised at higher oxygen levels performed better at all body temperatures and oxygen concentrations. Moreover, oxygen supply during testing had the greatest effect on flight performance at low temperature, rather than high temperature. Our results poorly support the hypothesis that oxygen supply limits performance at high temperatures, but do support the idea that hyperoxia during development improves performance of flies later in life.

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Date Created
  • 2017-05-23

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Indirect selection of thermal tolerance during experimental evolution of Drosophila melanogaster

Description

Natural selection alters the distribution of a trait in a population and indirectly alters the distribution of genetically correlated traits. Long-standing models of thermal adaptation assume that trade-offs exist between

Natural selection alters the distribution of a trait in a population and indirectly alters the distribution of genetically correlated traits. Long-standing models of thermal adaptation assume that trade-offs exist between fitness at different temperatures; however, experimental evolution often fails to reveal such trade-offs. Here, we show that adaptation to benign temperatures in experimental populations of Drosophila melanogaster resulted in correlated responses at the boundaries of the thermal niche. Specifically, adaptation to fluctuating temperatures (16–25°C) decreased tolerance of extreme heat. Surprisingly, flies adapted to a constant temperature of 25°C had greater cold tolerance than did flies adapted to other thermal conditions, including a constant temperature of 16°C. As our populations were never exposed to extreme temperatures during selection, divergence of thermal tolerance likely reflects indirect selection of standing genetic variation via linkage or pleiotropy. We found no relationship between heat and cold tolerances in these populations. Our results show that the thermal niche evolves by direct and indirect selection, in ways that are more complicated than assumed by theoretical models.

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Date Created
  • 2015-04-12

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Flies evolved small bodies and cells at high or fluctuating temperatures

Description

Recent theory predicts that the sizes of cells will evolve according to fluctuations in body temperature. Smaller cells speed metabolism during periods of warming but require more energy to maintain

Recent theory predicts that the sizes of cells will evolve according to fluctuations in body temperature. Smaller cells speed metabolism during periods of warming but require more energy to maintain and repair. To evaluate this theory, we studied the evolution of cell size in populations of Drosophila melanogaster held at either a constant temperature (16°C or 25°C) or fluctuating temperatures (16 and 25°C). Populations that evolved at fluctuating temperatures or a constant 25°C developed smaller thoraxes, wings, and cells than did flies exposed to a constant 16°C. The cells of flies from fluctuating environments were intermediate in size to those of flies from constant environments. Most genetic variation in cell size was independent of variation in wing size, suggesting that cell size was a target of selection. These evolutionary patterns accord with patterns of developmental plasticity documented previously. Future studies should focus on the mechanisms that underlie the selective advantage of small cells at high or fluctuating temperatures.

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Date Created
  • 2016-10-12

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Cold populations of flies evolved larger bodies and larger wings made of larger cells

Description

We examined the evolutionary morphological responses of Drosophila melanogaster that had evolved at constant cold (16°), constant hot (25°C), and fluctuating (16° and 25°C). Flies that were exposed to the

We examined the evolutionary morphological responses of Drosophila melanogaster that had evolved at constant cold (16°), constant hot (25°C), and fluctuating (16° and 25°C). Flies that were exposed to the constant low mean temperature developed larger thorax, wing, and cell sizes than those exposed to constant high mean temperatures. Males and females both responded similarly to thermal treatments in average wing and cell size. The resulting cell area for a given wing size in thermal fluctuating populations remains unclear and remains a subject for future research.

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Date Created
  • 2015-05

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Testing Rational Choice Theory through Arizona's "Move Over Law"

Description

States nationwide have implemented "Move Over Laws" to try and increase roadway safety, yet even with these laws, hundreds of people are killed each year while working in and roadways.

States nationwide have implemented "Move Over Laws" to try and increase roadway safety, yet even with these laws, hundreds of people are killed each year while working in and roadways. In Arizona, the "Move Over Law" requires drivers approaching a stopped vehicle displaying flashing lights to "move over" or "slow down." However, not everyone complies with this enacted law, and the purpose of this study is to observe how approaching drivers behave when presented with various scenarios. Scenarios involved the use of different police car types (marked or unmarked), light displays (no lights, hazards, or emergency lights), and the advertisement of Arizona's "Move Over Law" (signboard or no signboard). Associated risk varied with each scenario, and according to rational choice theory, a driver's behavior should minimize risks and maximize benefits. Under the hypothesis that police presence impacts driving behavior, the expectation was that driver compliance through "moving over" and/or slowing down would be highest when a marked police car or emergency lights were used. Also hypothesized was that awareness impacts compliance with the thought that increasing awareness by using a signboard would increase "move over" percentages and decrease speeds. From the test site along State Highway 260 in Payson, Arizona, the results indicate that car type and light display impact driving behavior. The use of the marked car or emergency lights generally had higher adjusted compliance, higher "move over" percentages, and lower speeds than when the unmarked car or no lights were tested. Looking at how awareness influences behavior, the use of the signboard had a greater impact when the unmarked car was used as opposed to the marked car. Based on the results, both hypotheses were supported.

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Date Created
  • 2017-05

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Muscles Serve as a Water Source for Egg Development in Children's Pythons (Antaresia childreni)

Description

Water-balance is a critical but understudied consideration for animals reproducing in dry environments, as females invest a significant amount of water into their offspring. What makes water especially challenging, is

Water-balance is a critical but understudied consideration for animals reproducing in dry environments, as females invest a significant amount of water into their offspring. What makes water especially challenging, is that few animals are known to have true water storage, whereas energy as fat storage is well-documented. Recent studies have suggested the possibility that, when drinking water is scarce, animals can catabolize their muscles, thereby extracting cellular water. In this study, the aim was to show this as a potential method used by animals reproducing in dry environments to cope with dehydration and still produce a clutch. Children's pythons (Antaresia childreni) were used to investigate this phenomenon due to the fact that they experience two, distinctive, reproductive phases- vitellogenesis (when protein and energy are mobilized and invested into the yolk) and gravidity (when the major water investment into the egg occurs, as well as egg shelling). Other factors that make them excellent candidates are that they are pure capital breeders (don't eat during the reproductive season) and can withstand periods of water deprivation that far outlast their reproductive gravid phase. Reproductive and non-reproductive females were deprived of water for the duration of gravidity, and their mass decrease, epaxial muscle shrinkage, blood osmolality, total protein, uric acid, triglycerides and ketones were measured at the onset of each reproductive stage; these values were compared to their water-provided counterparts. Water-deprived females experienced greater mass loss, epaxial muscle loss, blood plasma osmolality, and uric acid than water-provided females. These findings suggest that muscle catabolism is used as a method of dealing with water-deprivation during gravidity.

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Date Created
  • 2018-05

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Evaluating the presence of oxygen-limited thermal tolerance in Drosophila melanogaster at rest

Description

I am evaluating a notion that stems from a controversial hypothesis of heat stress. The oxygen- and capacity-limited thermal tolerance (OCLTT) hypothesis predicts a positive correlation between the tolerance of

I am evaluating a notion that stems from a controversial hypothesis of heat stress. The oxygen- and capacity-limited thermal tolerance (OCLTT) hypothesis predicts a positive correlation between the tolerance of hypoxia and the tolerance of heat in animals, where the notion claims that these animals must be metabolically active. To evaluate this notion, I tested heat coma recovery in several genetic lines of Drosophila melanogaster and compared it to data collected in prior studies. I hypothesized that the correlations between hypoxia tolerance and heat coma recovery would be similar to correlations found in Teague et al. (2017) and Fredette-Roman et al. (2020). After testing 65 lines from the Drosophila Genetic Reference Panel (DGRP), the notion was supported and provided evidence for the validity of OCLTT. Additional work is needed to enhance our understanding of the limitations of heat tolerance and doing such will generate more accurate models and predictions on how animals will respond to climate change.

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  • 2020-05

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Aedes aegypti Thermal Choice Experiment

Description

The non-native mosquito Aedes aegypti has become a common nuisance in Maricopa county. Associated with human settlement, Ae. aegypti is known to reproduce in standing water sources both indoors and

The non-native mosquito Aedes aegypti has become a common nuisance in Maricopa county. Associated with human settlement, Ae. aegypti is known to reproduce in standing water sources both indoors and outdoors, within vessels such as tires, flowerpots, and neglected swimming pools (Jansen & Beebe, 2010). Ae. aegypti and the related Ae. albopictus are the primary vectors of the arboviral diseases chikungunya, Zika, yellow fever and dengue. Ae. aegypti tends to blood feed multiple times per gonotrophic cycle (cycle of feeding and egg laying) which, alongside a preference for human blood and close association with human habitation, contributes to an increased risk of Ae. aegypti borne virus transmission (Scott & Takken, 2012). Between 2010-2017, 153 travel-associated cases of dengue were reported in the whole of Arizona (Rivera et al., 2020); while there have been no documented locally transmitted cases of Aedes borne diseases in Maricopa county, there are no apparent reasons why local transmission can’t occur in the future via local Aedes aegypti mosquitoes infected after feeding from travelling viremic hosts. Incidents of local dengue transmission in New York (Rivera et al., 2020) and Barcelona (European Center for Disease Control [ECDC], 2019) suggest that outbreaks of Aedes borne arbovirus’ can occur in regions more temperate than the current endemic range of Aedes borne diseases. Further, while the fact that Ae. aegypti eggs have a high mortality rate when exposed to cold temperatures limits the ability for Ae aegypti to establish stable breeding populations in temperate climates (Thomas, Obermayr, Fischer, Kreyling, & Beierkuhnlein, 2012), global increases in temperature will expand the possible ranges of Ae aegypti and Aedes borne diseases.

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Date Created
  • 2020-05

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The role of skill in determining dominance in the virile crayfish, Faxonius virilis

Description

Studies of animal contests often focus solely on a single static measurement of fighting ability, such as the size or the strength of the individual. However, recent studies have highlighted

Studies of animal contests often focus solely on a single static measurement of fighting ability, such as the size or the strength of the individual. However, recent studies have highlighted the importance of individual variation in the dynamic behaviors used during a fight, such as, assessment strategies, decision making, and fine motor control, as being strong predictors of the outcome of aggression. Here, I combined morphological and behavioral data to discover how these features interact during aggressing interactions in male virile crayfish, Faxonius virilis. I predicted that individual variation in behavioral skill for decision making (i.e., number of strikes thrown), would determine the outcome of contest success in addition to morphological measurements (e.g. body size, relative claw size). To evaluate this prediction, I filmed staged territorial interactions between male F. virilis and later analyzed trial behaviors (e.g. strike, pinches, and bout time) and aggressive outcomes. I found very little support for skill to predict win/loss outcome in trials. Instead, I found that larger crayfish engaged in aggression for longer compared to smaller crayfish, but that larger crayfish did not engage in a greater number of claw strikes or pinches when controlling for encounter duration. Future studies should continue to investigate the role of skill, by using finer-scale techniques such as 3D tracking software, which could track advanced measurements (e.g. speed, angle, and movement efficiency). Such studies would provide a more comprehensive understanding of the relative influence of fighting skill technique on territorial contests.

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Date Created
  • 2021-05

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Using Lactate as a Measure of Developmental Metabolism in Drosophila melanogaster

Description

Lactate is a commonly known biochemical that is usually produced under anaerobic conditions. This makes it a useful marker for examining the possibility that Drosophila melanogaster undergoes natural hypoxic states

Lactate is a commonly known biochemical that is usually produced under anaerobic conditions. This makes it a useful marker for examining the possibility that Drosophila melanogaster undergoes natural hypoxic states during development due to the rate of growth. To analyze this observation and its potential for explaining developmental changes, a lactate assay was used to quantify lactate produced across time points in the third larval instar and across early adulthood. Lactate assay results showed near-zero lactate levels for both larvae and adults. There were confounding factors present in larval lactate assays which made analysis difficult. However, the results of the adult lactate assays seem to indicate an inability to produce large amounts of lactate regardless of time point in adulthood, suggesting that adults do not naturally experience hypoxia during or after eclosion.

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Date Created
  • 2021-05