| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Brand, Jack A., et al.
(författare)
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Temperature change exerts sex-specific effects on behavioural variation
- 2023
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - 0962-8452 .- 1471-2954. ; 290:2002
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Tidskriftsartikel (refereegranskat)abstract
- Temperature is a key factor mediating organismal fitness and has important consequences for species' ecology. While the mean effects of temperature on behaviour have been well-documented in ectotherms, how temperature alters behavioural variation among and within individuals, and whether this differs between the sexes, remains unclear. Such effects likely have ecological and evolutionary consequences, given that selection acts at the individual level. We investigated the effect of temperature on individual-level behavioural variation and metabolism in adult male and female Drosophila melanogaster (n = 129), by taking repeated measures of locomotor activity and metabolic rate at both a standard temperature (25°C) and a high temperature (28°C). Males were moderately more responsive in their mean activity levels to temperature change when compared to females. However, this was not true for either standard or active metabolic rate, where no sex differences in thermal metabolic plasticity were found. Furthermore, higher temperatures increased both among- and within-individual variation in male, but not female, locomotor activity. Given that behavioural variation can be critical to population persistence, we suggest that future studies test whether sex differences in the amount of behavioural variation expressed in response to temperature change may result in sex-specific vulnerabilities to a warming climate.
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| 3. |
- Orford, Jack T., et al.
(författare)
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Bigger and bolder : Widespread agricultural pollutant 17β-trenbolone increases growth and alters behaviour in tadpoles (Litoria ewingii)
- 2023
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Ingår i: Aquatic Toxicology. - 0166-445X .- 1879-1514. ; 260
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Tidskriftsartikel (refereegranskat)abstract
- Endocrine-disrupting chemicals—compounds that directly interfere with the endocrine system of exposed animals—are insidious environmental pollutants that can disrupt hormone function, even at very low concentrations. The dramatic impacts that some endocrine-disrupting chemicals can have on the reproductive development of wildlife are well documented. However, the potential of endocrine-disrupting chemicals to disrupt animal behaviour has received far less attention, despite the important links between behavioural processes and population-level fitness. Accordingly, we investigated the impacts of 14 and 21-day exposure to two environmentally realistic levels of 17β-trenbolone (4.6 and 11.2 ng/L), a potent endocrine-disrupting steroid and agricultural pollutant, on growth and behaviour in tadpoles of an anuran amphibian, the southern brown tree frog (Litoria ewingii). We found that 17β-trenbolone altered morphology, baseline activity and responses to a predatory threat, but did not affect anxiety-like behaviours in a scototaxis assay. Specifically, we found that tadpoles exposed to our high-17β-trenbolone treatment were significantly longer and heavier at 14 and 21 days. We also found that tadpoles exposed to 17β-trenbolone showed higher levels of baseline activity, and significantly reduced their activity following a simulated predator strike. These results provide insights into the wider repercussions of agricultural pollutants on key developmental and behavioural traits in aquatic species, and demonstrate the importance of behavioural studies in the ecotoxicological field.
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| 4. |
- Orford, Jack T., et al.
(författare)
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Impacts of Exposure to Ultraviolet Radiation and an Agricultural Pollutant on Morphology and Behavior of Tadpoles (Limnodynastes tasmaniensis)
- 2024
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Ingår i: Environmental Toxicology and Chemistry. - 0730-7268 .- 1552-8618.
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Tidskriftsartikel (refereegranskat)abstract
- Amphibians are the most threatened vertebrate class globally. Multiple factors have been implicated in their global decline, and it has been hypothesized that interactions between stressors may be a major cause. Increased ultraviolet (UV) radiation, as a result of ozone depletion, has been identified as one such stressor. Exposure to UV radiation has been shown to have detrimental effects on amphibians and can exacerbate the effects of other stressors, such as chemical pollutants. Chemical pollution has likewise been recognized as a major factor contributing to amphibian declines, particularly, endocrine-disrupting chemicals. In this regard, 17 beta-trenbolone is a potent anabolic steroid used in the agricultural industry to increase muscle mass in cattle and has been repeatedly detected in the environment where amphibians live and breed. At high concentrations, 17 beta-trenbolone has been shown to impact amphibian survival and gonadal development. In the present study, we investigated the effects of environmentally realistic UV radiation and 17 beta-trenbolone exposure, both in isolation and in combination, on the morphology and behavior of tadpoles (Limnodynastes tasmaniensis). We found that neither stressor in isolation affected tadpoles, nor did we find any interactive effects. The results from our 17 beta-trenbolone treatment are consistent with recent research suggesting that, at environmentally realistic concentrations, tadpoles may be less vulnerable to this pollutant compared to other vertebrate classes. The absence of UV radiation-induced effects found in the present study could be due to species-specific variation in susceptibility, as well as the dosage utilized. We suggest that future research should incorporate long-term studies with multiple stressors to accurately identify the threats to, and subsequent consequences for, amphibians under natural conditions. Environ Toxicol Chem 2024;00:1-12. (c) 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
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| 5. |
- Polverino, Giovanni, et al.
(författare)
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Sex-specific effects of psychoactive pollution on behavioral individuality and plasticity in fish
- 2023
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Ingår i: Behavioral Ecology. - 1045-2249 .- 1465-7279. ; 34:6, s. 969-978
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Tidskriftsartikel (refereegranskat)abstract
- Lay Summary Prozac is present in freshwater systems across the globe as the pharmaceutical contaminant fluoxetine. The effect of fluoxetine on aquatic species' behavioral variability is not yet clear. We show that male guppies become more similar to each other after exposure to fluoxetine, and females become less flexible in their behavior. These sex-specific differences in response to fluoxetine can have a meaningful impact on their ability to survive in a changing world. The global rise of pharmaceutical contaminants in the aquatic environment poses a serious threat to ecological and evolutionary processes. Studies have traditionally focused on the collateral (average) effects of psychoactive pollutants on ecologically relevant behaviors of wildlife, often neglecting effects among and within individuals, and whether they differ between males and females. We tested whether psychoactive pollutants have sex-specific effects on behavioral individuality and plasticity in guppies (Poecilia reticulata), a freshwater species that inhabits contaminated waterways in the wild. Fish were exposed to fluoxetine (Prozac) for 2 years across multiple generations before their activity and stress-related behavior were repeatedly assayed. Using a Bayesian statistical approach that partitions the effects among and within individuals, we found that males-but not females-in fluoxetine-exposed populations differed less from each other in their behavior (lower behavioral individuality) than unexposed males. In sharp contrast, effects on behavioral plasticity were observed in females-but not in males-whereby exposure to even low levels of fluoxetine resulted in a substantial decrease (activity) and increase (freezing behavior) in the behavioral plasticity of females. Our evidence reveals that psychoactive pollution has sex-specific effects on the individual behavior of fish, suggesting that males and females might not be equally vulnerable to global pollutants.
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| 6. |
- Tan, Hung, et al.
(författare)
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No evidence that the widespread environmental contaminant caffeine alters energy balance or stress responses in fish
- 2023
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Ingår i: Ethology. - 0179-1613 .- 1439-0310. ; 129:12, s. 666-678
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic sources of environmental pollution are ever-increasing as urban areas expand and more chemical compounds are used in daily life. The stimulant caffeine is one of the most consumed chemical compounds worldwide, and as a result, has been detected as an environmental contaminant in all types of major water sources on all continents. Exposure of wildlife to environmental pollutants can disrupt the energy balance of these organisms, as restoration of homeostasis is prioritised. In turn, energy allocated to other key biological processes such as growth or reproduction may be affected, consequently reducing the overall fitness of an individual. Therefore, we aimed to investigate if long-term exposure to environmentally relevant concentrations of caffeine had any energetic consequences on wildlife. Specifically, we exposed wild eastern mosquitofish (Gambusia holbrooki) to one of three nominal concentrations of caffeine (0, 100 and 10,000 ng/L) and assayed individuals for metabolic rate, general activity, antipredator and foraging behaviour and body size as measures of energy expenditure or energy intake. We found no differences in any measured traits between any of the given exposure treatments, indicating that exposure to caffeine at current environmental levels may not adversely affect the energy balance and fitness of vulnerable freshwater fish.
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