The Experts below are selected from a list of 4218 Experts worldwide ranked by ideXlab platform
Patricia M Schulte - One of the best experts on this subject based on the ideXlab platform.
-
ionoregulatory aspects of the hypoxia induced osmorespiratory compromise in the euryhaline atlantic Killifish fundulus heteroclitus the effects of salinity
The Journal of Experimental Biology, 2020Co-Authors: Marina Giacomin, Patricia M Schulte, Chris M Wood, John O OnukwuforAbstract:The osmorespiratory compromise is a physiological trade-off between the characteristics of the gill that promote respiratory gas-exchange and those that limit passive fluxes of ions and water with the environment. In hypoxia, changes in gill blood flow patterns and functional surface area that increase gas transfer can promote an exacerbation in ion and water fluxes. Our goal was to determine whether the osmorespiratory compromise is flexible, depending on environmental salinity (fresh, isosmotic and sea water) and oxygen levels (hypoxia) in euryhaline Killifish, Fundulus heteroclitus. Plasma ion concentrations were minimally affected by hypoxia, indicating a maintenance of osmoregulatory homeostasis. In FW-Killifish, hypoxia exposure reduced branchial Na+/K+-ATPase and NEM-sensitive-ATPase activities, as well as diffusive water flux rates. Unidirectional Na+ influx and Na+ efflux decreased during hypoxia in FW, but net Na+ flux remained unchanged. Net loss rates of Cl−, K+ and ammonia were also attenuated in hypoxia, suggesting both transcellular and paracellular reductions in permeability. These reductions appeared to be regulated phenomena as fluxes were restored immediately in normoxia. Na+ flux rates increased during hypoxia in 11 ppt, but decreased in 35 ppt, the latter suggesting a similar response to hypoxia as in FW. In summary, FW- and SW-Killifish experience a reduction in gill permeability, as seen in other hypoxia-tolerant species. Fish acclimated to isosmotic salinity increased Na+ influx and efflux rates, as well as paracellular permeability in hypoxia, responses in accord with the predictions of the classic osmorespiratory compromise.
-
what is environmental stress insights from fish living in a variable environment
The Journal of Experimental Biology, 2014Co-Authors: Patricia M SchulteAbstract:Although the term environmental stress is used across multiple fields in biology, the inherent ambiguity associated with its definition has caused confusion when attempting to understand organismal responses to environmental change. Here I provide a brief summary of existing definitions of the term stress, and the related concepts of homeostasis and allostasis, and attempt to unify them to develop a general framework for understanding how organisms respond to environmental stressors. I suggest that viewing stressors as environmental changes that cause reductions in performance or fitness provides the broadest and most useful conception of the phenomenon of stress. I examine this framework in the context of animals that have evolved in highly variable environments, using the Atlantic Killifish, Fundulus heteroclitus, as a case study. Consistent with the extreme environmental variation that they experience in their salt marsh habitats, Killifish have substantial capacity for both short-term resistance and long-term plasticity in the face of changing temperature, salinity and oxygenation. There is inter-population variation in the sensitivity of Killifish to environmental stressors, and in their ability to acclimate, suggesting that local adaptation can shape the stress response even in organisms that are broadly tolerant and highly plastic. Whole-organism differences between populations in stressor sensitivity and phenotypic plasticity are reflected at the biochemical and molecular levels in Killifish, emphasizing the integrative nature of the response to environmental stressors. Examination of this empirical example highlights the utility of using an evolutionary perspective on stressors, stress and stress responses.
-
heat shock response of Killifish fundulus heteroclitus candidate gene and heterologous microarray approaches
Physiological Genomics, 2010Co-Authors: Timothy M Healy, Wendy E Tymchuk, Edward J Osborne, Patricia M SchulteAbstract:Northern and southern subspecies of the Atlantic Killifish, Fundulus heteroclitus, differ in maximal thermal tolerance. To determine whether these subspecies also differ in their heat shock respons...
-
countergradient variation in temperature preference in populations of Killifish fundulus heteroclitus
Physiological and Biochemical Zoology, 2009Co-Authors: Nann A Fangue, Jason E. Podrabsky, Larry I Crawshaw, Patricia M SchulteAbstract:Abstract Behavioral thermoregulation can allow ectotherms to buffer the effects of changes in environmental temperature, and thus an organism’s preferred temperature is thought to be under strong selection. However, this contention has seldom been tested. We used common Killifish Fundulus heteroclitus from high‐latitude (northern) and low‐latitude (southern) populations to investigate intraspecific variation in thermal preference and its relationship to habitat temperature. We quantified the preferred temperatures of northern and southern Killifish populations acclimated to three temperatures (5°, 15°, and 25°C) to evaluate two alternative hypotheses for the evolution of differences in thermal preference among latitudinally separated populations: local thermal adaptation, which predicts that organisms from high latitudes should prefer lower temperatures than individuals from lower latitudes, versus countergradient variation, which predicts that high‐latitude organisms should prefer higher temperatures to ...
-
swimming performance and energetics as a function of temperature in Killifish fundulus heteroclitus
Physiological and Biochemical Zoology, 2008Co-Authors: Nann A Fangue, Milica Mandic, Jeffrey G Richards, Patricia M SchulteAbstract:Abstract Populations of the common Killifish Fundulus heteroclitus are found along a latitudinal temperature gradient in habitats with high thermal variability. The objectives of this study were to assess the effects of temperature and population of origin on Killifish swimming performance (assessed as critical swimming speed, Ucrit). Acclimated fish from northern and southern Killifish populations demonstrated a wide zone (from 7° to 33°C) over which Ucrit showed little change with temperature, with performance declining significantly only at lower temperatures. Although we observed significant differences in swimming performance between a northern and a southern population of Killifish in one experiment, with northern fish having an ∼1.5‐fold‐greater Ucrit than southern fish across all acclimation temperatures, we were unable to replicate this finding in other populations or collection years, and performance was consistently high across all populations and at both low (7°C) and high (23°C) acclimation t...
Dario Riccardo Valenzano - One of the best experts on this subject based on the ideXlab platform.
-
intra species differences in population size shape life history and genome evolution
eLife, 2020Co-Authors: David Willemsen, Rongfeng Cui, Martin Reichard, Dario Riccardo ValenzanoAbstract:The evolutionary forces shaping life history divergence within species are largely unknown. Turquoise Killifish display differences in lifespan among wild populations, representing an ideal natural experiment in evolution and diversification of life history. By combining genome sequencing and population genetics, we investigate the evolutionary forces shaping lifespan among wild turquoise Killifish populations. We generate an improved reference genome assembly and identify genes under positive and purifying selection, as well as those evolving neutrally. Short-lived populations from the outer margin of the species range have small population size and accumulate deleterious mutations in genes significantly enriched in the WNT signaling pathway, neurodegeneration, cancer and the mTOR pathway. We propose that limited population size due to habitat fragmentation and repeated population bottlenecks, by increasing the genome-wide mutation load, exacerbates the effects of mutation accumulation and cumulatively contribute to the short adult lifespan.
-
antibody repertoire sequencing reveals systemic and mucosal immunosenescence in the short lived turquoise Killifish
bioRxiv, 2020Co-Authors: Dario Riccardo Valenzano, Michael Poeschla, William J Bradshaw, Aleksandra PlaczekAbstract:Aging individuals exhibit a pervasive decline in adaptive immune function, with important implications for health and lifespan. Previous studies have found a pervasive loss of immune-repertoire diversity in human peripheral blood; however, little is known about repertoire aging in other immune compartments, or in species other than humans. Here, we perform the first study of immune-repertoire aging in an emerging model of vertebrate aging, the African turquoise Killifish (Nothobranchius furzeri). Despite their extremely short lifespans, these Killifish exhibit complex and individualised heavy-chain repertoires, with a generative process capable of producing millions of productive receptor sequences. Whole-body Killifish repertoires decline rapidly in within-individual diversity with age, while between-individual variability increases. Large, expanded B-cell clones exhibit far greater diversity loss with age than small clones, suggesting an important difference in the age-sensitivity of different B-cell populations. Compared to the whole body, the immune repertoires of isolated intestinal samples exhibit much more dramatic age-related phenotypes, apparently due to an elevated prevalence of age-sensitive expanded clones. Our results highlight the importance of organ-specific dynamics in adaptive immunosenescence.
-
the turquoise Killifish a genetically tractable model for the study of aging
The Journal of Experimental Biology, 2020Co-Authors: Dario Riccardo Valenzano, Michael PoeschlaAbstract:ABSTRACT Lifespan is a remarkably diverse trait in nature, ranging from just hours in adult mayflies to hundreds of years in the Greenland shark and quahog clam. Great disparities in lifespan are often observed even among somewhat closely related species; for example, in the laboratory, wild-derived strains of the common house mouse have a maximum observed lifespan of approximately 6 years, while a similarly sized rodent, the naked mole rat, can live for over 30 years. Comparative biology of aging across the tree of life provides a tremendous opportunity for understanding the molecular and genetic basis underlying lifespan and aging. However, a lack of molecular and laboratory tools has limited the ability of researchers to take full advantage of the incredible diversity of aging phenotypes in nature. Recent developments in genomic technology have made it increasingly possible to study non-canonical model organisms for aging. One promising new genetic model organism amenable to a range of experimental interventions is the turquoise Killifish (Nothobranchius furzeri). This fish species has a naturally short lifespan and undergoes a wide range of aging-related transformations. These fish have a fully sequenced genome and transcriptome, and Killifish embryos are accessible to transgenesis and genome editing. Furthermore, different Killifish species and populations show striking differences in lifespan, providing the opportunity for comparative analysis of aging. This Review introduces the natural life history of the turquoise Killifish, its emerging applicability as an aging model system, the genetic tools that have been developed to study aging for this species and a summary of recent studies facilitated by these new tools.
-
intra species differences in population size shape life history and genome evolution
bioRxiv, 2019Co-Authors: David Willemsen, Rongfeng Cui, Martin Reichard, Dario Riccardo ValenzanoAbstract:The evolutionary forces shaping life history trait divergence within species are largely unknown. Killifish (oviparous Cyprinodontiformes) evolved an annual life cycle as an exceptional adaptation to life in arid savannah environments characterized by seasonal water availability. The turquoise Killifish (Nothobranchius furzeri) is the shortest-lived vertebrate known to science and displays differences in lifespan among wild populations, representing an ideal natural experiment in the evolution and diversification of life history. Here, by combining genome sequencing and population genetics, we investigate the evolutionary forces shaping lifespan among turquoise Killifish populations. We generate an improved reference assembly for the turquoise Killifish genome, trace the evolutionary origin of the sex chromosome, and identify genes under strong positive and purifying selection, as well as those evolving neutrally. We find that the shortest-lived turquoise Killifish populations, which dwell in fragmented and isolated habitats at the outer margin of the geographical range of the species, are characterized by small effective population size and accumulate throughout the genome several small to large-effect deleterious mutations due to genetic drift. The genes most affected by drift in the shortest-lived turquoise Killifish populations are involved in the WNT signalling pathway, neurodegenerative disorders, cancer and the mTOR pathway. As the populations under stronger genetic drift are the shortest-lived ones, we propose that limited population size due to habitat fragmentation and repeated population bottlenecks, by causing the genome-wide accumulation of deleterious mutations, cumulatively contribute to the short adult lifespan in turquoise Killifish populations.
-
efficient genome engineering approaches for the short lived african turquoise Killifish
Nature Protocols, 2016Co-Authors: Itamar Harel, Dario Riccardo Valenzano, Anne BrunetAbstract:A central challenge in experimental aging research is the lack of short-lived vertebrate models for genetic studies. Here we present a comprehensive protocol for efficient genome engineering in the African turquoise Killifish (Nothobranchius furzeri), which is the shortest-lived vertebrate in captivity with a median life span of 4-6 months. By taking advantage of the clustered regularly interspaced short palindromic repeats/CRISPR-associated protein-9 nuclease (CRISPR/Cas9) system and the turquoise Killifish genome, this platform enables the generation of knockout alleles via nonhomologous end joining (NHEJ) and knock-in alleles via homology-directed repair (HDR). We include guidelines for guide RNA (gRNA) target design, embryo injection and hatching, germ-line transmission and for minimizing off-target effects. We also provide strategies for Tol2-based transgenesis and large-scale husbandry conditions that are critical for success. Because of the fast life cycle of the turquoise Killifish, stable lines can be generated as rapidly as 2-3 months, which is much faster than other fish models. This protocol provides powerful genetic tools for studying vertebrate aging and aging-related diseases.
Richard T. Di Giulio - One of the best experts on this subject based on the ideXlab platform.
-
the role of gut microbial community and metabolomic shifts in adaptive resistance of atlantic Killifish fundulus heteroclitus to polycyclic aromatic hydrocarbons
Science of The Total Environment, 2021Co-Authors: Lauren K Redfern, Richard T. Di Giulio, Nishad Jayasundara, David R Singleton, James Carlson, Susan Sumner, Claudia K GunschAbstract:Altered gut microbiomes may play a role in rapid evolution to anthropogenic change but remain poorly understood. Atlantic Killifish (Fundulus heteroclitus) in the Elizabeth River, VA have evolved resistance to polycyclic aromatic hydrocarbons (PAHs) and provide a unique opportunity to examine the links between shifts in the commensal microbiome and organismal physiology associated with evolved resistance. Here, 16S rRNA sequence libraries derived from fish guts and sediments sampled from a highly PAH contaminated site revealed significant differences collected at similar samples from an uncontaminated site. Phylogenetic groups enriched in the libraries derived from PAH-resistant fish were dissimilar to their associated sediment libraries, suggesting the specific environment within the PAH-resistant fish intestine influence the gut microbiome composition. Gut metabolite analysis revealed shifts between PAH-resistant and non-resistant subpopulations. Notably, PAH-resistant fish exhibited reduced levels of tryptophan and increased levels of sphingolipids. Exposure to PAHs appears to impact several bacterial in the gut microbiome, particularly sphingolipid containing bacteria. Bacterial phylotypes known to include species containing sphingolipids were generally lower in the intestines of fish subpopulations exposed to high concentrations of PAHs, inferring a complex host-microbiome relationship. Overall, Killifish microbial community shifts appear to be related to a suppression of overall metabolite level, indicating a potential role of the gut in organismal response to anthropogenic environmental change. These results on microbial and metabolomics shifts are potentially linked to altered bioenergetic phenotype observed in the same PAH-resistant Killifish populations in other studies.
-
hepatic responses of juvenile fundulus heteroclitus from pollution adapted and nonadapted populations exposed to elizabeth river sediment extract
Toxicologic Pathology, 2016Co-Authors: Amanda K Riley, Daniel R Brown, Melissa Chernick, David E Hinton, Richard T. Di GiulioAbstract:Atlantic Killifish (Fundulus heteroclitus) inhabiting the Atlantic Wood Industries region of the Elizabeth River, Virginia, have passed polycyclic aromatic hydrocarbon (PAH) resistance to their offspring as evidenced by early life stage testing of developmental toxicity after exposure to specific PAHs. Our study focused on environmentally relevant PAH mixtures in the form of Elizabeth River sediment extract (ERSE). Juvenile (5 month) F1 progeny of pollution-adapted Atlantic Wood (AW) parents and of reference site (King's Creek [KC]) parents were exposed as embryos to ERSE. Liver alterations, including nonneoplastic lesions and microvesicular vacuolation, were observed in both populations. ERSE-exposed KC fish developed significantly more alterations than unexposed KC fish. Interestingly, unexposed AW Killifish developed significantly more alterations than unexposed KC individuals, suggesting that AW juveniles are not fully protected from liver disease; rapid growth of juvenile fish may also be an accelerating factor for tumorigenesis. Because recent reports show hepatic tumor formation in adult AW fish, the differing responses from the 2 populations provided a way to determine whether embryo toxicity protection extends to juveniles. Future investigations will analyze older life stages of Killifish to determine differences in responses related to chronic disease.
-
silver nanoparticle toxicity to atlantic Killifish fundulus heteroclitus and caenorhabditis elegans a comparison of mesocosm microcosm and conventional laboratory studies
Environmental Toxicology and Chemistry, 2015Co-Authors: Audrey J Bone, Cole W. Matson, Joel N Meyer, Benjamin P Colman, Xinyu Yang, Richard T. Di GiulioAbstract:The use of silver nanoparticles (AgNPs) in consumer products and industrial applications, as well as their recent detection in waste streams, has created concern about potential impacts on aquatic ecosystems. The effect of complex environmental media on AgNP toxicity was investigated using wetland mesocosms and smaller scale microcosms. Mesocosms were dosed with 2.5 mg Ag/L as gum arabic (GA)-coated AgNPs, polyvinylpyrrolidone (PVP)-coated AgNPs, or AgNO3. Water samples were taken from mesocosms 24 h after dosing for acute toxicity tests with embryos and larvae of Atlantic Killifish (Fundulus heteroclitus) and the nematode Caenorhabditis elegans. Acute toxicity tests were also performed on Atlantic Killifish with AgNO3, GA AgNPs, and PVP AgNPs prepared in the laboratory with similar water. For Killifish embryos, mesocosm samples were much less toxic than laboratory samples for all types of silver. For larvae, in contrast, all 3 silver mesocosm treatments exhibited toxicity. Interestingly, mesocosm samples of AgNO3 were less toxic than laboratory samples; samples containing GA AgNPs were similar in toxicity, and samples containing PVP AgNPs were more toxic. For C. elegans, results were similar to Killifish larvae. Results obtained from the mesocosms were not replicated on the smaller scale of the microcosms. These results indicate that environmental factors unique to the mesocosms acted differentially on AgNO3 to reduce its toxicity in a manner that does not translate to AgNPs for larval fish. Environ Toxicol Chem 2014;9999:1–9. © 2014 SETAC
-
compound and mixture specific differences in resistance to polycyclic aromatic hydrocarbons and pcb 126 among fundulus heteroclitus subpopulations throughout the elizabeth river estuary virginia usa
Environmental Science & Technology, 2013Co-Authors: Bryan W. Clark, Heather M Stapleton, Ellen M Cooper, Richard T. Di GiulioAbstract:Atlantic Killifish (Fundulus heteroclitus) inhabiting the Atlantic Wood Industries Superfund Site (Elizabeth River, Portsmouth, VA, USA) are resistant to the acute toxicity and cardiac teratogenesis caused by high levels of polycyclic aromatic hydrocarbons (PAHs) from creosote. The resistance is linked to down regulation of the aryl hydrocarbon receptor (AHR) pathway. We investigated the association between CYP1 activity, as a marker of potential AHR pathway suppression, and contaminant resistance in Killifish subpopulations from sites throughout the estuary that varied significantly in PAH contamination level. Adult Killifish and sediments were collected from seven sites across approximately 13.7 km in river length within the estuary and from a nearby reference site. Sediment PAH levels were determined using gas chromatography mass spectrometry. Embryos obtained via manual spawning were exposed to individual AHR agonists and PAH mixtures 24 h post fertilization (hpf); CYP1 activity was determined by in o...
-
genotoxicity in atlantic Killifish fundulus heteroclitus from a pah contaminated superfund site on the elizabeth river virginia
Ecotoxicology, 2011Co-Authors: Cole W. Matson, Dawoon Jung, Leonard B Collins, Geoff Laban, Heather M Stapleton, John W Bickham, James A Swenberg, Richard T. Di GiulioAbstract:The Atlantic Wood Industries Superfund site (AWI) on the Elizabeth River in Portsmouth, VA is heavily contaminated with polycyclic aromatic hydrocarbons (PAHs) from a wood treatment facility. Atlantic Killifish, or mummichog (Fundulus heteroclitus), at this Superfund site are exposed to very high concentrations of several carcinogens. In this study, we measured PAH concentrations in both fish tissues and sediments. Concurrently, we assessed different aspects of genotoxicity in the Killifish exposed in situ. Both sediment and tissue PAH levels were significantly higher in AWI samples, relative to a reference site, but the chemistry profile was different between sediments and tissues. Killifish at AWI exhibited higher levels of DNA damage compared to reference fish, as measured via the flow cytometric method (FCM), and the damage was consistent with sediment PAH concentrations. Covalent binding of benzo[a]pyrene (BaP) metabolites to DNA, as measured via LC–MS/MS adduct detection methods, were also elevated and could be partially responsible for the DNA damage. Using similar LC–MS/MS methods, we found no evidence that oxidative DNA adducts had a role in observed genotoxicity.
Chris M Wood - One of the best experts on this subject based on the ideXlab platform.
-
ionoregulatory aspects of the hypoxia induced osmorespiratory compromise in the euryhaline atlantic Killifish fundulus heteroclitus the effects of salinity
The Journal of Experimental Biology, 2020Co-Authors: Marina Giacomin, Patricia M Schulte, Chris M Wood, John O OnukwuforAbstract:The osmorespiratory compromise is a physiological trade-off between the characteristics of the gill that promote respiratory gas-exchange and those that limit passive fluxes of ions and water with the environment. In hypoxia, changes in gill blood flow patterns and functional surface area that increase gas transfer can promote an exacerbation in ion and water fluxes. Our goal was to determine whether the osmorespiratory compromise is flexible, depending on environmental salinity (fresh, isosmotic and sea water) and oxygen levels (hypoxia) in euryhaline Killifish, Fundulus heteroclitus. Plasma ion concentrations were minimally affected by hypoxia, indicating a maintenance of osmoregulatory homeostasis. In FW-Killifish, hypoxia exposure reduced branchial Na+/K+-ATPase and NEM-sensitive-ATPase activities, as well as diffusive water flux rates. Unidirectional Na+ influx and Na+ efflux decreased during hypoxia in FW, but net Na+ flux remained unchanged. Net loss rates of Cl−, K+ and ammonia were also attenuated in hypoxia, suggesting both transcellular and paracellular reductions in permeability. These reductions appeared to be regulated phenomena as fluxes were restored immediately in normoxia. Na+ flux rates increased during hypoxia in 11 ppt, but decreased in 35 ppt, the latter suggesting a similar response to hypoxia as in FW. In summary, FW- and SW-Killifish experience a reduction in gill permeability, as seen in other hypoxia-tolerant species. Fish acclimated to isosmotic salinity increased Na+ influx and efflux rates, as well as paracellular permeability in hypoxia, responses in accord with the predictions of the classic osmorespiratory compromise.
-
mechanisms of ca 2 uptake in freshwater and seawater acclimated Killifish fundulus heteroclitus and their response to acute salinity transfer
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2019Co-Authors: Alex M Zimmer, Kevin V Brix, Chris M WoodAbstract:Killifish (Fundulus heteroclitus) has been extensively used as a model for ion regulation by euryhaline fishes. Na+ and Cl− dynamics have been well studied in Killifish, but few studies have addressed that of Ca2+. Therefore, this study aimed to characterize Ca2+ fluxes in freshwater (FW) and seawater (SW)-acclimated Killifish, their response to salinity transfer, and to elucidate the mechanisms of Ca2+ influx in FW and SW. SW Killifish displayed a significantly higher Ca2+ influx rate than that of FW fish, while Ca2+ efflux rates were comparable in both salinities. Ca2+ influx was saturable in FW (Km = 78 ± 19 µmol/L; Jmax = 53 ± 3 nmol/g/h) and influx by SW Killifish was linear up to 7 mmol/L Ca2+. In SW-acclimated fish, 36% of Ca2+ influx was attributed to “intestinal Ca2+ intake”, likely caused by drinking, whereas intestinal Ca2+ intake in FW contributed to < 2% of total. Throughout the study, results suggested that “cation competition” in SW modulates Ca2+ influx. Therefore, we hypothesized that SW-acclimated fish actually have a higher affinity Ca2+ influx system than FW-acclimated fish but that it is competitively inhibited by competing SW cations. In agreement with this cation competition hypothesis, we demonstrated for the first time that “extra-intestinal” Ca2+ influx was inhibited by Mg2+ in both FW and SW-acclimated Killifish. Following acute salinity transfer, extra-intestinal Ca2+ influx was rapidly regulated within 12–24 h, similar to Na+ and Cl−. Ca2+ influx in FW was inhibited by La3+, an epithelial Ca2+ channel blocker, whereas La3+ had no significant effect in SW.
-
investigating the mechanisms of ni uptake and sub lethal toxicity in the atlantic Killifish fundulus heteroclitus in relation to salinity
Environmental Pollution, 2016Co-Authors: Tamzin A Blewett, Chris M Wood, Victoria E Ransberry, Grant B McclellandAbstract:The Atlantic Killifish (Fundulus heteroclitus) is a resilient estuarine species that may be subjected to anthropogenic contamination of its natural habitat, by toxicants such as nickel (Ni). We investigated Ni accumulation and potential modes of Ni toxicity, in Killifish, as a function of environmental salinity. Killifish were acclimated to 4 different salinities [0 freshwater (FW), 10, 30 and 100% seawater (SW)] and exposed to 5 mg/L of Ni for 96 h. Tissue Ni accumulation, whole body ions, critical swim speed and oxidative stress parameters were examined. SW was protective against Ni accumulation in the gills and kidney. Addition of Mg and Ca to FW protected against gill Ni accumulation, suggesting competition with Ni for uptake. Concentration-dependent Ni accumulation in the gill exhibited saturable relationships in both FW- and SW-acclimated fish. However SW fish displayed a lower Bmax (i.e. lower number of Ni binding sites) and a lower Km (i.e. higher affinity for Ni binding). No effect of Ni exposure was observed on critical swim speed (Ucrit) or maximum rate of oxygen consumption (MO2max). Markers of oxidative stress showed either no effect (e.g. protein carbonyl formation), or variable effects that appeared to depend more on salinity than on Ni exposure. These data indicate that the Killifish is very tolerant to Ni toxicity, a characteristic that may facilitate the use of this species as a site-specific biomonitor of contaminated estuaries.
-
salinity dependent nickel accumulation and oxidative stress responses in the euryhaline Killifish fundulus heteroclitus
Archives of Environmental Contamination and Toxicology, 2015Co-Authors: Tamzin A Blewett, Chris M WoodAbstract:The mechanisms of nickel (Ni) toxicity in marine fish remain unclear, although evidence from freshwater (FW) fish suggests that Ni can act as a pro-oxidant. This study investigated the oxidative stress effects of Ni on the euryhaline Killifish (Fundulus heteroclitus) as a function of salinity. Killifish were exposed to sublethal levels (5, 10, and 20 mg L(-1)) of waterborne Ni for 96 h in FW (0 ppt) and 100 % saltwater (SW) (35 ppt). In general, SW was protective against both Ni accumulation and indicators of oxidative stress [protein carbonyl formation and catalase (CAT) activity]. This effect was most pronounced at the highest Ni exposure level. For example, FW intestine showed increased Ni accumulation relative to SW intestine at 20 mg Ni L(-1), and this was accompanied by significantly greater protein carbonylation and CAT activity in this tissue. There were exceptions, however, in that although liver of FW Killifish at the highest exposure concentration showed greater Ni accumulation relative to SW liver, levels of CAT activity were greatly decreased. This may relate to tissue- and salinity-specific differences in oxidative stress responses. The results of the present study suggest (1) that there was Ni-induced oxidative stress in Killifish, (2) that the effects of salinity depend on differences in the physiology of the fish in FW versus SW, and (3) that increased levels of cations (sodium, calcium, potassium, and magnesium) and anions (SO4 and Cl) in SW are likely protective against Ni accumulation in tissues exposed to the aquatic environment.
Nann A Fangue - One of the best experts on this subject based on the ideXlab platform.
-
countergradient variation in temperature preference in populations of Killifish fundulus heteroclitus
Physiological and Biochemical Zoology, 2009Co-Authors: Nann A Fangue, Jason E. Podrabsky, Larry I Crawshaw, Patricia M SchulteAbstract:Abstract Behavioral thermoregulation can allow ectotherms to buffer the effects of changes in environmental temperature, and thus an organism’s preferred temperature is thought to be under strong selection. However, this contention has seldom been tested. We used common Killifish Fundulus heteroclitus from high‐latitude (northern) and low‐latitude (southern) populations to investigate intraspecific variation in thermal preference and its relationship to habitat temperature. We quantified the preferred temperatures of northern and southern Killifish populations acclimated to three temperatures (5°, 15°, and 25°C) to evaluate two alternative hypotheses for the evolution of differences in thermal preference among latitudinally separated populations: local thermal adaptation, which predicts that organisms from high latitudes should prefer lower temperatures than individuals from lower latitudes, versus countergradient variation, which predicts that high‐latitude organisms should prefer higher temperatures to ...
-
swimming performance and energetics as a function of temperature in Killifish fundulus heteroclitus
Physiological and Biochemical Zoology, 2008Co-Authors: Nann A Fangue, Milica Mandic, Jeffrey G Richards, Patricia M SchulteAbstract:Abstract Populations of the common Killifish Fundulus heteroclitus are found along a latitudinal temperature gradient in habitats with high thermal variability. The objectives of this study were to assess the effects of temperature and population of origin on Killifish swimming performance (assessed as critical swimming speed, Ucrit). Acclimated fish from northern and southern Killifish populations demonstrated a wide zone (from 7° to 33°C) over which Ucrit showed little change with temperature, with performance declining significantly only at lower temperatures. Although we observed significant differences in swimming performance between a northern and a southern population of Killifish in one experiment, with northern fish having an ∼1.5‐fold‐greater Ucrit than southern fish across all acclimation temperatures, we were unable to replicate this finding in other populations or collection years, and performance was consistently high across all populations and at both low (7°C) and high (23°C) acclimation t...
-
intraspecific variation in thermal tolerance and heat shock protein gene expression in common Killifish fundulus heteroclitus
The Journal of Experimental Biology, 2006Co-Authors: Nann A Fangue, Myriam Hofmeister, Patricia M SchulteAbstract:SUMMARY Populations of common Killifish, Fundulus heteroclitus , are distributed along the Atlantic coast of North America through a steep latitudinal thermal gradient. We examined intraspecific variation in whole-animal thermal tolerance and its relationship to the heat shock response in Killifish from the northern and southern extremes of the species range. Critical thermal maxima were significantly higher in southern than in northern fish by ∼1.5°C at a wide range of acclimation temperatures (from 2-34°C), and critical thermal minima differed by ∼1.5°C at acclimation temperatures above 22°C, converging on the freezing point of brackish water at lower acclimation temperatures. To determine whether these differences in whole-organism thermal tolerance were reflected in differences in either the sequence or regulation of the heat shock protein genes ( hsps ) we obtained complete cDNA sequences for hsc70 , hsp70-1 and hsp70-2 , and partial sequences of hsp90 α and hsp90 β. There were no fixed differences in amino acid sequence between populations in either hsp70-1 or hsp70-2 , and only a single conservative substitution between populations in hsc70 . By contrast, there were significant differences between populations in the expression of many, but not all, of these genes. Both northern and southern Killifish significantly increased hsp70-2 levels above control values ( T on ) at a heat shock temperature of 33°C, but the magnitude of this induction was greater in northern fish, suggesting that northern fish may be more susceptible to thermal damage than are southern fish. In contrast, hsp70-1 mRNA levels increased gradually and to the same extent in response to heat shock in both populations. Hsc70 mRNA levels were significantly elevated by heat shock in southern fish, but not in northern fish. Similarly, the more thermotolerant southern Killifish had a T on for hsp90 α of 30°C, 2°C lower than that of northern fish. This observation combined with the ability of southern Killifish to upregulate hsc70 in response to heat shock suggests a possible role for these hsps in whole-organism differences in thermal tolerance. These data highlight the importance of considering the complexity of the heat shock response across multiple isoforms when attempting to make linkages to whole-organism traits such as thermal tolerance.
-
intraspecific variation in thermal tolerance and heat shock protein gene expression in common Killifish fundulus heteroclitus
The Journal of Experimental Biology, 2006Co-Authors: Nann A Fangue, Myriam Hofmeister, Patricia M SchulteAbstract:Populations of common Killifish, Fundulus heteroclitus, are distributed along the Atlantic coast of North America through a steep latitudinal thermal gradient. We examined intraspecific variation in whole-animal thermal tolerance and its relationship to the heat shock response in Killifish from the northern and southern extremes of the species range. Critical thermal maxima were significantly higher in southern than in northern fish by approximately 1.5 degrees C at a wide range of acclimation temperatures (from 2-34 degrees C), and critical thermal minima differed by approximately 1.5 degrees C at acclimation temperatures above 22 degrees C, converging on the freezing point of brackish water at lower acclimation temperatures. To determine whether these differences in whole-organism thermal tolerance were reflected in differences in either the sequence or regulation of the heat shock protein genes (hsps) we obtained complete cDNA sequences for hsc70, hsp70-1 and hsp70-2, and partial sequences of hsp90alpha and hsp90beta. There were no fixed differences in amino acid sequence between populations in either hsp70-1 or hsp70-2, and only a single conservative substitution between populations in hsc70. By contrast, there were significant differences between populations in the expression of many, but not all, of these genes. Both northern and southern Killifish significantly increased hsp70-2 levels above control values (T(on)) at a heat shock temperature of 33 degrees C, but the magnitude of this induction was greater in northern fish, suggesting that northern fish may be more susceptible to thermal damage than are southern fish. In contrast, hsp70-1 mRNA levels increased gradually and to the same extent in response to heat shock in both populations. Hsc70 mRNA levels were significantly elevated by heat shock in southern fish, but not in northern fish. Similarly, the more thermotolerant southern Killifish had a T(on) for hsp90alpha of 30 degrees C, 2 degrees C lower than that of northern fish. This observation combined with the ability of southern Killifish to upregulate hsc70 in response to heat shock suggests a possible role for these hsps in whole-organism differences in thermal tolerance. These data highlight the importance of considering the complexity of the heat shock response across multiple isoforms when attempting to make linkages to whole-organism traits such as thermal tolerance.
