Search

Search Results

• 1. [Article] Antioxidant enzyme response in rainbow trout (Oncorhynchus mykiss) after subchronic exposure to an environmentally-relevant polycyclic aromatic hydrocarbon mixture

  Polycyclic aromatic hydrocarbons (PAHs) are significant pollutants in aquatic environments. Many are carcinogenic and lead to DNA fragmentation and adduct formation in marine and freshwater organisms. ...

  Citation × Citation Citation Abstract Copy Title: Antioxidant enzyme response in rainbow trout (Oncorhynchus mykiss) after subchronic exposure to an environmentally-relevant polycyclic aromatic hydrocarbon mixture Author: Norby, Tyler S. Polycyclic aromatic hydrocarbons (PAHs) are significant pollutants in aquatic environments. Many are carcinogenic and lead to DNA fragmentation and adduct formation in marine and freshwater organisms. Previous research demonstrates that rainbow trout (Oncorhynchus mykiss) compensate to long-term PAH dietary exposures and reduce the DNA damage. The aim of this study was to assess whether upregulation of detoxifying/antioxidant enzymes in rainbow trout at least partially explains compensation to PAH exposure that allows for this reduction in DNA damage. Rainbow trout were fed a diet that contained a mixture of nine high molecular weight PAHs in environmentally relevant ratios and concentrations. Two doses were used: a lower dose of 20 parts per million (ppm) and a higher dose of 200 ppm. Two other treatment formulations were also used containing 20 ppm and 200 ppm concentrations of benzo(α)pyrene. A control group of rainbow trout was also used. 80 rainbow trout per PAH treatment and control were used in this experiment. The fish were fed PAH treatment diets or a control diet daily beginning when their average weight was 20 g. At days 7, 14, 28 and 42 enough fish were sacrificed from each of the four treatment groups plus control to obtain four 1 g pooled liver samples. Body and liver weights were recorded for each sacrificed fish. Various biomarkers and detoxifying/antioxidant enzyme activities were measured. Lipid peroxidation was estimated for all sample groups using a thiobarbituric acidreactive substances (TBARS) assay. NAD(P)H:quinone oxidoreductase 1 [DTdiaphorase], also known as quinone reductase (QR), activities were determined for all sample groups using a modified photometric assay that defines QR levels as the dicoumarol-inhibitable reduction of 2,6-dichlorophenolindophenol (DCPIP). Glutathione peroxidase (GPOX) activities were determined for all sample groups using a modified photometric assay that defines GPOX levels as the reduction of NADPH in cytosolic liver fractions. Catalase (CAT) activities were determined for all sample groups using an assay kit that utilized the reaction CAT has with methanol in the presence of hydrogen peroxide. CAT showed the strongest significant (P < 0.05) response, rising and falling over the time-course of the study in a dose-dependent sinusoidal decay pattern as the system moved toward optimal steady-state activity. GPOX activities increased significantly (P < 0.05) over the time-course of treatments, also showing a sinusoidal decay pattern similar to that seen with CAT, although the GPOX activity followed a slower decay pattern than CAT and was not dose-dependent. QR activities were low overall. This indicated that this detoxifying enzyme was not a major component of the trout’s adaptive response. The TBARS assay was determined to be an insensitive assay for fish tissues due to the harshness and unspecific nature of the test. The mass-spectroscopy-based F2-isoprostanes assay was determined to be a much more appropriate assay for the determination of lipid peroxide levels in fish tissues, based on previous research. Title: Antioxidant enzyme response in rainbow trout (Oncorhynchus mykiss) after subchronic exposure to an environmentally-relevant polycyclic aromatic hydrocarbon mixture Author: Norby, Tyler S. Polycyclic aromatic hydrocarbons (PAHs) are significant pollutants in aquatic environments. Many are carcinogenic and lead to DNA fragmentation and adduct formation in marine and freshwater organisms. Previous research demonstrates that rainbow trout (Oncorhynchus mykiss) compensate to long-term PAH dietary exposures and reduce the DNA damage. The aim of this study was to assess whether upregulation of detoxifying/antioxidant enzymes in rainbow trout at least partially explains compensation to PAH exposure that allows for this reduction in DNA damage. Rainbow trout were fed a diet that contained a mixture of nine high molecular weight PAHs in environmentally relevant ratios and concentrations. Two doses were used: a lower dose of 20 parts per million (ppm) and a higher dose of 200 ppm. Two other treatment formulations were also used containing 20 ppm and 200 ppm concentrations of benzo(α)pyrene. A control group of rainbow trout was also used. 80 rainbow trout per PAH treatment and control were used in this experiment. The fish were fed PAH treatment diets or a control diet daily beginning when their average weight was 20 g. At days 7, 14, 28 and 42 enough fish were sacrificed from each of the four treatment groups plus control to obtain four 1 g pooled liver samples. Body and liver weights were recorded for each sacrificed fish. Various biomarkers and detoxifying/antioxidant enzyme activities were measured. Lipid peroxidation was estimated for all sample groups using a thiobarbituric acidreactive substances (TBARS) assay. NAD(P)H:quinone oxidoreductase 1 [DTdiaphorase], also known as quinone reductase (QR), activities were determined for all sample groups using a modified photometric assay that defines QR levels as the dicoumarol-inhibitable reduction of 2,6-dichlorophenolindophenol (DCPIP). Glutathione peroxidase (GPOX) activities were determined for all sample groups using a modified photometric assay that defines GPOX levels as the reduction of NADPH in cytosolic liver fractions. Catalase (CAT) activities were determined for all sample groups using an assay kit that utilized the reaction CAT has with methanol in the presence of hydrogen peroxide. CAT showed the strongest significant (P < 0.05) response, rising and falling over the time-course of the study in a dose-dependent sinusoidal decay pattern as the system moved toward optimal steady-state activity. GPOX activities increased significantly (P < 0.05) over the time-course of treatments, also showing a sinusoidal decay pattern similar to that seen with CAT, although the GPOX activity followed a slower decay pattern than CAT and was not dose-dependent. QR activities were low overall. This indicated that this detoxifying enzyme was not a major component of the trout’s adaptive response. The TBARS assay was determined to be an insensitive assay for fish tissues due to the harshness and unspecific nature of the test. The mass-spectroscopy-based F2-isoprostanes assay was determined to be a much more appropriate assay for the determination of lipid peroxide levels in fish tissues, based on previous research. Close

• 2. [Article] The influence of sex, migration distance, and latitude on expression of anadromy in Oncorhynchus mykiss

  The evolution and maintenance of multiple phenotypes within populations is an interesting evolutionary and ecological question, and is becoming increasingly important for the restoration and conservation ...

  Citation × Citation Citation Abstract Copy Title: The influence of sex, migration distance, and latitude on expression of anadromy in Oncorhynchus mykiss Author: Ohms, Haley The evolution and maintenance of multiple phenotypes within populations is an interesting evolutionary and ecological question, and is becoming increasingly important for the restoration and conservation of partially migratory species. In particular, why individuals adopt a particular phenotype has been the focus of numerous research efforts. In the partially migratory species Oncorhynchys mykiss (commonly known as steelhead and rainbow trout), I found that sex plays a strong role in whether an individual adopts an anadromous or resident life history. I observed a higher frequency of females adopting the anadromous tactic throughout the species range, and I attributed this to the relationship between body size and reproductive success in females that is not present in males. I did not observe differences in female bias along gradients of latitude or migration distance, and I hypothesize that while the frequency of tactics among populations may change along these gradients, either the change is equal between males and females, or an interaction of latitude and migration distance may control changes. I did not observe a corresponding male bias in the one resident population I sampled, and suggest that this is the result of a high frequency of residents in that population. I propose that sex ratios could be a valuable metric for measuring frequency of life-history tactics in populations and could facilitate the investigation into the controls of life-history tactics across broad scales. Title: The influence of sex, migration distance, and latitude on expression of anadromy in Oncorhynchus mykiss Author: Ohms, Haley The evolution and maintenance of multiple phenotypes within populations is an interesting evolutionary and ecological question, and is becoming increasingly important for the restoration and conservation of partially migratory species. In particular, why individuals adopt a particular phenotype has been the focus of numerous research efforts. In the partially migratory species Oncorhynchys mykiss (commonly known as steelhead and rainbow trout), I found that sex plays a strong role in whether an individual adopts an anadromous or resident life history. I observed a higher frequency of females adopting the anadromous tactic throughout the species range, and I attributed this to the relationship between body size and reproductive success in females that is not present in males. I did not observe differences in female bias along gradients of latitude or migration distance, and I hypothesize that while the frequency of tactics among populations may change along these gradients, either the change is equal between males and females, or an interaction of latitude and migration distance may control changes. I did not observe a corresponding male bias in the one resident population I sampled, and suggest that this is the result of a high frequency of residents in that population. I propose that sex ratios could be a valuable metric for measuring frequency of life-history tactics in populations and could facilitate the investigation into the controls of life-history tactics across broad scales. Close

• 3. [Article] Born to run? Integrating individual behavior, physiology, and life histories in partially migratory steelhead and rainbow trout (Oncorhynchus mykiss)

  Steelhead and rainbow trout are common names for marine-migratory (anadromous) and freshwater-resident forms of Oncorhynchus mykiss, a partially migratory salmonid fish. Anadromous and resident forms are ...

  Citation × Citation Citation Abstract Copy Title: Born to run? Integrating individual behavior, physiology, and life histories in partially migratory steelhead and rainbow trout (Oncorhynchus mykiss) Author: Sloat, Matthew R. Steelhead and rainbow trout are common names for marine-migratory (anadromous) and freshwater-resident forms of Oncorhynchus mykiss, a partially migratory salmonid fish. Anadromous and resident forms are sympatric and can produce offspring with a life history different from their own (i.e., steelhead parents can produce rainbow trout offspring and vice versa). The expression of these alternative life histories is a plastic response to individual patterns of energy acquisition, assimilation, and allocation during juvenile life stages. Individual performance during early stream life is of particular interest because of potential carry-over effects on subsequent growth and developmental trajectories. In a series of experiments in laboratory streams, I determined the influence of individual variation in energy metabolism on behavior, growth, and life-history expression in O. mykiss. Individual variation in energy metabolism was a strong predictor of feeding territory acquisition by juvenile fish during the transition from dependence on maternal provisioning of egg yolk reserves to independent feeding. Feeding territory acquisition was positively associated with standard metabolic rate (SMR) under conditions of an abundant and predictable food supply. When the density of intraspecific competitors was manipulated, the association between SMR and territory acquisition was strongest at intermediate stocking densities, moderate at the highest stocking densities, and weakest at the lowest stocking densities. However, reducing the spatial predictability of food resources within streams reversed the influence of SMR on competitive outcomes. These experiments determined that variation in ecological conditions during early life stages imposes different selection regimes on juvenile O. mykiss and results in physiological divergence among cohorts. Subsequent rearing experiments determined that behavioral dominance influences rates of anadromy and freshwater maturation, most likely through the association between SMR and territory acquisition. In addition to the effects of behavioral dominance, I observed a significant influence of sex, rearing temperature, and individual growth trajectories on the expression of anadromy and freshwater maturation. Partially migratory populations of O. mykiss maintain an exceptionally diverse portfolio of life-history strategies. Results from this work lend insight into a suite of behavioral and physiological processes influencing individual life histories. Title: Born to run? Integrating individual behavior, physiology, and life histories in partially migratory steelhead and rainbow trout (Oncorhynchus mykiss) Author: Sloat, Matthew R. Steelhead and rainbow trout are common names for marine-migratory (anadromous) and freshwater-resident forms of Oncorhynchus mykiss, a partially migratory salmonid fish. Anadromous and resident forms are sympatric and can produce offspring with a life history different from their own (i.e., steelhead parents can produce rainbow trout offspring and vice versa). The expression of these alternative life histories is a plastic response to individual patterns of energy acquisition, assimilation, and allocation during juvenile life stages. Individual performance during early stream life is of particular interest because of potential carry-over effects on subsequent growth and developmental trajectories. In a series of experiments in laboratory streams, I determined the influence of individual variation in energy metabolism on behavior, growth, and life-history expression in O. mykiss. Individual variation in energy metabolism was a strong predictor of feeding territory acquisition by juvenile fish during the transition from dependence on maternal provisioning of egg yolk reserves to independent feeding. Feeding territory acquisition was positively associated with standard metabolic rate (SMR) under conditions of an abundant and predictable food supply. When the density of intraspecific competitors was manipulated, the association between SMR and territory acquisition was strongest at intermediate stocking densities, moderate at the highest stocking densities, and weakest at the lowest stocking densities. However, reducing the spatial predictability of food resources within streams reversed the influence of SMR on competitive outcomes. These experiments determined that variation in ecological conditions during early life stages imposes different selection regimes on juvenile O. mykiss and results in physiological divergence among cohorts. Subsequent rearing experiments determined that behavioral dominance influences rates of anadromy and freshwater maturation, most likely through the association between SMR and territory acquisition. In addition to the effects of behavioral dominance, I observed a significant influence of sex, rearing temperature, and individual growth trajectories on the expression of anadromy and freshwater maturation. Partially migratory populations of O. mykiss maintain an exceptionally diverse portfolio of life-history strategies. Results from this work lend insight into a suite of behavioral and physiological processes influencing individual life histories. Close

• 4. [Article] Demographic and phenotypic responses of juvenile steelhead trout to spatial predictability of food resources

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Ecological ...

  Citation × Citation Citation Abstract Copy Title: Demographic and phenotypic responses of juvenile steelhead trout to spatial predictability of food resources Author: Reeves, Gordon H., Sloat, Matthew R. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Ecological Society of America and can be found at: http://www.esajournals.org/loi/ecol. Supplemental Material can be found at: http://www.esapubs.org/archive/ecol/E095/215/ Title: Demographic and phenotypic responses of juvenile steelhead trout to spatial predictability of food resources Author: Reeves, Gordon H., Sloat, Matthew R. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Ecological Society of America and can be found at: http://www.esajournals.org/loi/ecol. Supplemental Material can be found at: http://www.esapubs.org/archive/ecol/E095/215/ Close