Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 17 de 17
Filter
Add more filters










Publication year range
1.
J Health Commun ; 29(5): 319-326, 2024 May 03.
Article in English | MEDLINE | ID: mdl-38590206

ABSTRACT

This study interrogates the nature by which media perpetuates and potentially preempts stigma about military-related posttraumatic stress. Indeed, addressing the stigma of mental illness is critical to facilitating veteran comfort in seeking needed mental health care. Therefore, the authors explored how media messages about veterans experiencing posttraumatic stress (PTS) influenced how veterans viewed themselves, other veterans experiencing PTS and overall support for government policy and intervention. An experimental design was used to assess how veterans' perceptions are affected by messages adhering to the principles of the model of stigma communication, as well as its more prosocial counterpart, what the authors coin as halo communication. Findings reveal evidence that stigma messages more potently influence outcome perceptions relative to comparable halo messages in the current context. Additionally, interactive effects of message exposure (i.e. conditioned by perceived association with PTS identity) were observed on views that government health intervention is warranted for veterans managing PTS. Practical and theoretical implications are discussed.


Subject(s)
Mass Media , Social Stigma , Stress Disorders, Post-Traumatic , Veterans , Humans , Veterans/psychology , Stress Disorders, Post-Traumatic/psychology , Male , Female , Adult , Middle Aged , Health Communication/methods , Communication , United States , Military Personnel/psychology
2.
Health Commun ; 39(3): 439-450, 2024 Mar.
Article in English | MEDLINE | ID: mdl-36693816

ABSTRACT

Prior research demonstrates an influence of culpability framing on news consumers' perceptions about, and willingness to provide support for, those managing illness. Framing research of this sort has typically focused on the effect of frames on a particular health context (e.g. cancer). It is necessary to examine how three health frames which are overwhelmingly represented in health news could be uniquely influencing perceptions about those managing illness in a number of disparate health contexts. Specifically, we explore the nature of health frame influence as it relates to news reports regarding alcoholism, morbid obesity, and cancer. These illnesses represent the three of the most prominent health concerns for Americans that also vary in terms of how they relate to four chief cues for stigma communication. Experimental findings reveal unique ways in which culpability framing influences social support dispositions for those managing illness, as a function of intergroup anxiety perceptions.


Subject(s)
Mass Media , Neoplasms , Humans , Community Support , Social Stigma , Communication , Neoplasms/therapy
3.
Proc Biol Sci ; 290(1998): 20230106, 2023 05 10.
Article in English | MEDLINE | ID: mdl-37132237

ABSTRACT

Understanding how animals respond to large-scale environmental changes is difficult to achieve because monitoring data are rarely available for more than the past few decades, if at all. Here, we demonstrate how a variety of palaeoecological proxies (e.g. isotopes, geochemistry and DNA) from an Andean Condor (Vultur gryphus) guano deposit from Argentina can be used to explore breeding site fidelity and the impacts of environmental changes on avian behaviour. We found that condors used the nesting site since at least approximately 2200 years ago, with an approximately 1000-year nesting frequency slowdown from ca 1650 to 650 years before the present (yr BP). We provide evidence that the nesting slowdown coincided with a period of increased volcanic activity in the nearby Southern Volcanic Zone, which resulted in decreased availability of carrion and deterred scavenging birds. After returning to the nest site ca 650 yr BP, condor diet shifted from the carrion of native species and beached marine animals to the carrion of livestock (e.g. sheep and cattle) and exotic herbivores (e.g. red deer and European hare) introduced by European settlers. Currently, Andean Condors have elevated lead concentrations in their guano compared to the past, which is associated with human persecution linked to the shift in diet.


Subject(s)
Deer , Falconiformes , Humans , Animals , Cattle , Sheep , Anthropogenic Effects , Birds , Diet
4.
J Microbiol Methods ; 172: 105901, 2020 05.
Article in English | MEDLINE | ID: mdl-32199876

ABSTRACT

Diatoms are one of the earth's major oxygen producers. For that reason, studying the floating phenomena of living diatom cells in water is an important research subject. Efficiency of photosynthesis of diatom cells may be heavily affected by their floating behavior. In our previous research, we devised a 'tumbled' microscope, a device created by tilting an inverted microscope (CKX53, OLYMPUS) by 90 degrees, due to which allowed observation with a sample stage perpendicular to the ground. When we observed a Petri dish filled with diatom cell suspension, the floating behavior of diatom cells were well visualized. Cyclotella meneghiniana was isolated and subcultured in bold modified basal freshwater nutrient solution liquid medium (B5282-500ML, Sigma-Aldrich) at 18 °C. Before the microscopic observation, cell suspension was cultured for two weeks after the final subculture. Observation was performed at room temperature, 30 °C, and 40 °C with a temperature sensor in the center of the chamber (inside). Observations were started as soon as the sample was installed. In a typical image obtained using the tumbled microscope, the diatom cells were found to move from the top to the bottom. In order to analyze floating velocity and trajectory, observation was continued for 35 min at room temperature, 30 °C, and 40 °C. Tracking analysis was carried out using the two-dimensional motion image measurement software Move-tr/2D. The average speed of 100 cells was 7.0 ± 4.3 µm/s at room temperature, 85.6 ± 31.9 µm/s at 30 °C and 470.1 ± 279.8 µm/s at 40 °C. In this study, we devised the unique observation to visualize the temperature dependence of diatom cells.


Subject(s)
Diatoms/isolation & purification , Microscopy/methods , Temperature , Cell Culture Techniques/methods , Diatoms/growth & development , Fresh Water , Microscopy/instrumentation
5.
Mar Drugs ; 16(8)2018 Aug 20.
Article in English | MEDLINE | ID: mdl-30127281

ABSTRACT

Coccolithophores are unicellular marine phytoplankton, which produce intricate, tightly regulated, exoskeleton calcite structures. The formation of biogenic calcite occurs either intracellularly, forming 'wheel-like' calcite plates, or extracellularly, forming 'tiled-like' plates known as coccoliths. Secreted coccoliths then self-assemble into multiple layers to form the coccosphere, creating a protective wall around the organism. The cell wall hosts a variety of unique species-specific inorganic morphologies that cannot be replicated synthetically. Although biomineralisation has been extensively studied, it is still not fully understood. It is becoming more apparent that biologically controlled mineralisation is still an elusive goal. A key question to address is how nature goes from basic building blocks to the ultrafine, highly organised structures found in coccolithophores. A better understanding of coccolithophore biomineralisation will offer new insight into biomimetic and bioinspired synthesis of advanced, functionalised materials for bone tissue regeneration. The purpose of this review is to spark new interest in biomineralisation and gain new insight into coccolithophores from a material science perspective, drawing on existing knowledge from taxonomists, geologists, palaeontologists and phycologists.


Subject(s)
Bone Regeneration/physiology , Calcification, Physiologic/physiology , Phytoplankton/physiology , Animals , Biomimetics/methods , Calcium Carbonate/metabolism
6.
Syst Biol ; 67(1): 49-60, 2018 Jan 01.
Article in English | MEDLINE | ID: mdl-29253296

ABSTRACT

Scientists building the Tree of Life face an overwhelming challenge to categorize phenotypes (e.g., anatomy, physiology) from millions of living and fossil species. This biodiversity challenge far outstrips the capacities of trained scientific experts. Here we explore whether crowdsourcing can be used to collect matrix data on a large scale with the participation of nonexpert students, or "citizen scientists." Crowdsourcing, or data collection by nonexperts, frequently via the internet, has enabled scientists to tackle some large-scale data collection challenges too massive for individuals or scientific teams alone. The quality of work by nonexpert crowds is, however, often questioned and little data have been collected on how such crowds perform on complex tasks such as phylogenetic character coding. We studied a crowd of over 600 nonexperts and found that they could use images to identify anatomical similarity (hypotheses of homology) with an average accuracy of 82% compared with scores provided by experts in the field. This performance pattern held across the Tree of Life, from protists to vertebrates. We introduce a procedure that predicts the difficulty of each character and that can be used to assign harder characters to experts and easier characters to a nonexpert crowd for scoring. We test this procedure in a controlled experiment comparing crowd scores to those of experts and show that crowds can produce matrices with over 90% of cells scored correctly while reducing the number of cells to be scored by experts by 50%. Preparation time, including image collection and processing, for a crowdsourcing experiment is significant, and does not currently save time of scientific experts overall. However, if innovations in automation or robotics can reduce such effort, then large-scale implementation of our method could greatly increase the collective scientific knowledge of species phenotypes for phylogenetic tree building. For the field of crowdsourcing, we provide a rare study with ground truth, or an experimental control that many studies lack, and contribute new methods on how to coordinate the work of experts and nonexperts. We show that there are important instances in which crowd consensus is not a good proxy for correctness.


Subject(s)
Classification/methods , Crowdsourcing/standards , Phylogeny , Animals , Phenotype , Professional Competence , Reproducibility of Results
7.
PLoS One ; 12(11): e0187692, 2017.
Article in English | MEDLINE | ID: mdl-29117268

ABSTRACT

Salmonella can survive for long periods under extreme desiccation conditions. This stress tolerance poses a risk for food safety, but relatively little is known about the molecular and cellular regulation of this adaptation mechanism. To determine the genetic components involved in Salmonella's cellular response to desiccation, we performed a global transcriptomic analysis comparing S. enterica serovar Typhimurium cells equilibrated to low water activity (aw 0.11) and cells equilibrated to high water activity (aw 1.0). The analysis revealed that 719 genes were differentially regulated between the two conditions, of which 290 genes were up-regulated at aw 0.11. Most of these genes were involved in metabolic pathways, transporter regulation, DNA replication/repair, transcription and translation, and, more importantly, virulence genes. Among these, we decided to focus on the role of sopD and sseD. Deletion mutants were created and their ability to survive desiccation and exposure to aw 0.11 was compared to the wild-type strain and to an E. coli O157:H7 strain. The sopD and sseD mutants exhibited significant cell viability reductions of 2.5 and 1.3 Log (CFU/g), respectively, compared to the wild-type after desiccation for 4 days on glass beads. Additional viability differences of the mutants were observed after exposure to aw 0.11 for 7 days. E. coli O157:H7 lost viability similarly to the mutants. Scanning electron microscopy showed that both mutants displayed a different morphology compared to the wild-type and differences in production of the extracellular matrix under the same conditions. These findings suggested that sopD and sseD are required for Salmonella's survival during desiccation.


Subject(s)
Bacterial Proteins/genetics , Gene Expression Regulation, Bacterial , Salmonella typhimurium/genetics , Salmonella typhimurium/pathogenicity , Virulence Factors/genetics , Adaptation, Physiological/genetics , Bacterial Proteins/metabolism , Desiccation , Gene Deletion , Gene Expression Profiling , Microscopy, Electron, Scanning , Salmonella typhimurium/metabolism , Salmonella typhimurium/ultrastructure , Stress, Physiological/genetics , Transcriptome , Virulence Factors/deficiency
8.
Sci Rep ; 7(1): 14138, 2017 10 26.
Article in English | MEDLINE | ID: mdl-29075005

ABSTRACT

Porous silica is an attractive biomaterial in many applications, including drug-delivery systems, bone-graft fillers and medical devices. The issue with porous silica biomaterials is the rate at which they resorb and the significant role played by interfacial chemistry on the host response in vivo. This paper explores the potential of diatom-biosilica as a model tool to assist in the task of mapping and quantifying the role of surface topography and chemical cues on cell fate. Diatoms are unicellular microalgae whose cell walls are composed of, amorphous nanopatterned biosilica that cannot be replicated synthetically. Their unique nanotopography has the potential to improve understanding of interface reactions between materials and cells. This study used Cyclotella meneghiniana as a test subject to assess cytotoxicity and pro-inflammatory reactions to diatom-biosilica. The results suggest that diatom-biosilica is non-cytotoxic to J774.2 macrophage cells, and supports cell proliferation and growth. The addition of amine and thiol linkers have shown a significant effect on cytotoxicity, growth and cytokine response, thus warranting further investigation into the interfacial effects of small chemical modifications to substrate surfaces. The overall findings suggest diatom-biosilica offers a unique platform for in-depth investigation of the role played by nanotopography and chemistry in biomedical applications.


Subject(s)
Biocompatible Materials/pharmacology , Diatoms/chemistry , Macrophages/drug effects , Silicon Dioxide/pharmacology , Animals , Biocompatible Materials/chemistry , Cell Line , Cell Proliferation/drug effects , Cytokines/metabolism , Diatoms/ultrastructure , Hydrogen-Ion Concentration , Macrophages/cytology , Macrophages/metabolism , Mice, Inbred BALB C , Microscopy, Electron, Scanning , Photoelectron Spectroscopy , Silanes/chemistry , Silicon Dioxide/pharmacokinetics , Species Specificity , Sulfhydryl Compounds/chemistry , Sulfur/analysis
9.
Health Commun ; 29(1): 41-50, 2014.
Article in English | MEDLINE | ID: mdl-23356571

ABSTRACT

The Internet is one of the fastest growing news sources for many worldwide (Pew Research Center's Project for Excellence in Journalism, 2011), and cancer news is one frequently consumed form of online health information (Google, Inc., 2007). This content analysis of online cancer news (n = 862) retrieved from the four most frequented news websites describes trends regarding specific cancers, stages in the cancer continuum, and types of news articles. In general, treatment information received the most attention in online cancer news. Breast cancer received the most attention of each specific cancer, followed by digestive and genitourinary cancers. Research reports and profiles of people (more than 60% of which were about celebrities) were the most common article types. Risk, uncertainty, and clinical trials were also present across several types of cancer news articles. Implications of content trends are discussed as relevant to consumers, producers, health campaign designers, and researchers alike.


Subject(s)
Bibliometrics , Information Dissemination , Internet/trends , Neoplasms , Communications Media/trends , Humans , Information Dissemination/methods
10.
PLoS Curr ; 52013 Jun 26.
Article in English | MEDLINE | ID: mdl-23827969

ABSTRACT

The phenotype represents a critical interface between the genome and the environment in which organisms live and evolve. Phenotypic characters also are a rich source of biodiversity data for tree building, and they enable scientists to reconstruct the evolutionary history of organisms, including most fossil taxa, for which genetic data are unavailable. Therefore, phenotypic data are necessary for building a comprehensive Tree of Life. In contrast to recent advances in molecular sequencing, which has become faster and cheaper through recent technological advances, phenotypic data collection remains often prohibitively slow and expensive. The next-generation phenomics project is a collaborative, multidisciplinary effort to leverage advances in image analysis, crowdsourcing, and natural language processing to develop and implement novel approaches for discovering and scoring the phenome, the collection of phentotypic characters for a species. This research represents a new approach to data collection that has the potential to transform phylogenetics research and to enable rapid advances in constructing the Tree of Life. Our goal is to assemble large phenomic datasets built using new methods and to provide the public and scientific community with tools for phenomic data assembly that will enable rapid and automated study of phenotypes across the Tree of Life.

11.
J Phycol ; 48(2): 270-4, 2012 Apr.
Article in English | MEDLINE | ID: mdl-27009716

ABSTRACT

The eutrophic, freshwater diatom species Stephanodiscus binderanus (Kütz.) Willi Krieg. has long been considered a nuisance exotic alga introduced from Eurasia to the Great Lakes in North America in the early to mid-20th century. However, our paleolimnological data from Lake Simcoe, Ontario, provide unequivocal evidence that this taxon has been present in the Great Lakes region since at least the late 17th century. Subfossil diatom valves were identified and enumerated at high resolution in (210) Pb-dated sediment cores from four sites across the lake. The taxonomic identification of S. binderanus was confirmed using SEM. The historical presence of this species in Lake Simcoe indicates somewhat naturally productive conditions and also refutes the idea that S. binderanus is a nonindigenous species to North America. This study underscores the caution that should be applied to questions of diatom (and protistan) distributions in time and space. Clearly, the absence of evidence is not evidence of absence.

12.
BMC Evol Biol ; 11: 125, 2011 May 14.
Article in English | MEDLINE | ID: mdl-21569560

ABSTRACT

BACKGROUND: Publication of the first diatom genome, that of Thalassiosira pseudonana, established it as a model species for experimental and genomic studies of diatoms. Virtually every ensuing study has treated T. pseudonana as a marine diatom, with genomic and experimental data valued for their insights into the ecology and evolution of diatoms in the world's oceans. RESULTS: The natural distribution of T. pseudonana spans both marine and fresh waters, and phylogenetic analyses of morphological and molecular datasets show that, 1) T. pseudonana marks an early divergence in a major freshwater radiation by diatoms, and 2) as a species, T. pseudonana is likely ancestrally freshwater. Marine strains therefore represent recent recolonizations of higher salinity habitats. In addition, the combination of a relatively nondescript form and a convoluted taxonomic history has introduced some confusion about the identity of T. pseudonana and, by extension, its phylogeny and ecology. We resolve these issues and use phylogenetic criteria to show that T. pseudonana is more appropriately classified by its original name, Cyclotella nana. Cyclotella contains a mix of marine and freshwater species and so more accurately conveys the complexities of the phylogenetic and natural histories of T. pseudonana. CONCLUSIONS: The multitude of physical barriers that likely must be overcome for diatoms to successfully colonize freshwaters suggests that the physiological traits of T. pseudonana, and the genes underlying those traits, might differ from those of strictly marine diatoms. The freshwater ancestry of T. pseudonana might therefore confound generalizations about the physiological and metabolic properties of marine diatoms. The freshwater component of T. pseudonana's history merits careful consideration in the interpretation of experimental data collected for this important model species.


Subject(s)
Diatoms/genetics , Diatoms/ultrastructure , Fresh Water , Hydrobiology , Phylogeny
13.
Integr Comp Biol ; 50(6): 1185-99, 2010 Dec.
Article in English | MEDLINE | ID: mdl-21558266

ABSTRACT

Environmental pressures may vary over the geographic range of a species, exposing subpopulations to divergent functional demands. How does exposure to competing demands shape the morphology of species and influence the divergence of populations? We explored these questions by performing selection experiments on juveniles of the Hawaiian goby Sicyopterus stimpsoni, an amphidromous fish that exhibits morphological differences across portions of its geographic range where different environmental pressures predominate. Juvenile S. stimpsoni face two primary and potentially opposing selective pressures on body shape as they return from the ocean to freshwater streams on islands: (1) avoiding predators in the lower reaches of a stream; and (2) climbing waterfalls to reach the habitats occupied by adults. These pressures differ in importance across the Hawaiian Islands. On the youngest island, Hawai'i, waterfalls are close to shore, thereby minimizing exposure to predators and placing a premium on climbing performance. In contrast, on the oldest major island, Kaua'i, waterfalls have eroded further inland, lengthening the exposure of juveniles to predators before migrating juveniles begin climbing. Both juvenile and adult fish show differences in body shape between these islands that would be predicted to improve evasion of predators by fish from Kaua'i (e.g., taller bodies that improve thrust) and climbing performance for fish from Hawai'i (e.g., narrower bodies that reduce drag), matching the prevailing environmental demand on each island. To evaluate how competing selection pressures and functional tradeoffs contribute to the divergence in body shape observed in S. stimpsoni, we compared selection imposed on juvenile body shape by (1) predation by the native fish Eleotris sandwicensis versus (2) climbing an artificial waterfall (∼100 body lengths). Some variables showed opposing patterns of selection that matched predictions: for example, survivors of predation had lower fineness ratios than did control fish (i.e., greater body depth for a given length), whereas successful climbers had higher fineness ratios (reducing drag) than did fish that failed. However, most morphological variables showed significant selection in only one treatment rather than opposing selection across both. Thus, functional tradeoffs between evasion of predators and minimizing drag during climbing might influence divergence in body shape across subpopulations, but even when selection is an important contributing mechanism, directly opposite patterns of selection across environmental demands are not required to generate morphological divergence.


Subject(s)
Body Size , Locomotion , Perciformes/anatomy & histology , Perciformes/genetics , Selection, Genetic , Animals , Ecosystem , Food Chain , Hawaii , Rivers , Species Specificity , Water Movements
14.
Environ Toxicol Chem ; 28(12): 2677-84, 2009 Dec.
Article in English | MEDLINE | ID: mdl-19405782

ABSTRACT

The effects of embryonic and larval exposure to environmentally relevant (ng/L) concentrations of common antidepressants, fluoxetine, sertraline, venlafaxine, and bupropion (singularly and in mixture) on C-start escape behavior were evaluated in fathead minnows (Pimephales promelas). Embryos (postfertilization until hatching) were exposed for 5 d and, after hatching, were allowed to grow in control well water until 12 d old. Similarly, posthatch fathead minnows were exposed for 12 d to these compounds. High-speed (1,000 frames/s) video recordings of escape behavior were collected and transferred to National Institutes of Health Image for frame-by-frame analysis of latency periods, escape velocities, and total escape response (combination of latency period and escape velocity). When tested 12 d posthatch, fluoxetine and venlafaxine adversely affected C-start performance of larvae exposed as embryos. Conversely, larvae exposed for 12 d posthatch did not exhibit altered escape responses when exposed to fluoxetine but were affected by venlafaxine and bupropion exposure. Mixtures of these four antidepressant pharmaceuticals slowed predator avoidance behaviors in larval fathead minnows regardless of the exposure window. The direct impact of reduced C-start performance on survival and, ultimately, reproductive fitness provides an avenue to assess the ecological relevance of exposure in an assay of relatively short duration.


Subject(s)
Antidepressive Agents/toxicity , Escape Reaction/drug effects , Water Pollutants, Chemical/toxicity , Animals , Cyprinidae/embryology , Dopamine/physiology , Larva/drug effects , Predatory Behavior , Serotonin/physiology
15.
Aquat Toxicol ; 91(4): 355-61, 2009 Mar 09.
Article in English | MEDLINE | ID: mdl-19162341

ABSTRACT

Aquatic organisms exposed to endocrine disrupting compounds (EDCs) at early life-stages may have reduced reproductive fitness via disruption of reproductive and non-reproductive behavioral and physiological pathways. Survival to reproductive age relies upon optimal non-reproductive trait expression, such as adequate predator avoidance responses, which may be impacted through EDC exposure. During a predator-prey confrontation, larval fish use an innate C-start escape behavior to rapidly move away from an approaching threat. We tested the hypotheses that (1) larval fathead minnows exposed to estrogens, a primary class of EDCs, singularly or in mixture, suffer a reduced ability to perform an innate C-start behavior when faced with a threat stimulus; (2) additive effects will cause greater reductions in C-start behavior; and (3) effects will differ among developmental stages. In this study, embryos (post-fertilization until hatching) were exposed for 5 days to environmentally relevant concentrations of estrone (E1), 17beta-estradiol (E2), and 17alpha-ethinylestradiol (EE2) singularly and in mixture. Exposed embryos were allowed to hatch and grow in control well water until 12 days old. Similarly, post-hatch fathead minnows were exposed for 12 days to these compounds. High-speed (1000frames/s) video recordings of escape behavior were collected and transferred to National Institutes of Health Image for frame-by-frame analysis of latency period, escape velocity, and total escape response (combination of latency period and escape velocity). When tested 12 days post-hatch, only E1 adversely affected C-start performance of larvae exposed as embryos. Conversely, larvae exposed for 12 days post-hatch did not exhibit altered escape responses when exposed to E1, while adverse responses were seen in E2 and the estrogen mixture. Ethinylestradiol exposure did not elicit changes in escape behaviors at either developmental stage. The direct impact of reduced C-start performance on survival, and ultimately, reproductive fitness provides an avenue to assess the ecological relevance of exposure in an assay of relatively short duration.


Subject(s)
Cyprinidae/physiology , Escape Reaction/drug effects , Estrogens/toxicity , Larva/drug effects , Water Pollutants, Chemical/toxicity , Animals , Embryo, Nonmammalian/drug effects
16.
Integr Comp Biol ; 48(6): 734-49, 2008 Dec.
Article in English | MEDLINE | ID: mdl-21669829

ABSTRACT

Flow characteristics are a prominent factor determining body shapes in aquatic organisms, and correlations between body shape and ambient flow regimes have been established for many fish species. In this study, we investigated the potential for a brief period of extreme flow to exert selection on the body shape of juvenile climbing Hawaiian gobiid fishes. Because of an amphidromous life history, juvenile gobies that complete an oceanic larval phase return to freshwater habitats, where they become adults. Returning juveniles often must scale waterfalls (typically with the use of a ventral sucker) in order to reach the habitats they will use as adults, thereby exposing these animals to brief periods of extreme velocities of flow. Hydrodynamic theory predicts that bodies with larger suckers and with lower heights that reduce drag would have improved climbing success and, thus, be well suited to meet the demands of the flows in waterfalls. To test the potential for the flow environment of waterfalls to impose selection that could contribute to differences in body shape between islands, we subjected juvenile Sicyopterus stimpsoni to climbing trials up artificial waterfalls (∼100 body lengths) and measured differences in body shape between successful and unsuccessful climbers. Waterfalls appear to represent a significant selective barrier to these fishes, as nearly 30% failed our climbing test. However, the effects of selection on morphology were not straightforward, as significant differences in shape between successful and unsuccessful climbers did not always match hydrodynamic predictions. In both selection experiments and in adult fish collected from habitats with different prevailing conditions of flow (the islands of Hawai'i versus Kaua'i), lower head heights were associated with exposure to high-flow regimes, as predicted by hydrodynamic theory. Thus, a premium appears to be placed on the reduction of drag via head morphology throughout the ontogeny of this species. The congruence of phenotypic selection patterns observed in our experiments, with morphological character divergence documented among adult fish from Hawai'i and Kaua'i, suggests that differences in morphology between subpopulations of adult climbing gobies may result, at least in part, from the selective pressures of high-velocity flows encountered by migrating juveniles.

17.
Aquat Toxicol ; 85(1): 19-27, 2007 Nov 15.
Article in English | MEDLINE | ID: mdl-17826850

ABSTRACT

Estrogenic compounds have been discovered in many surface water samples in many anthropogenically altered surface waters. Wastewater effluent has been identified as a major pathway of contamination and found to revert much of the metabolic products of these biologically active compounds back to their original form. This presentation explains methodology for determining exposure effects through a newly developed bioassay, examining the physiological response of a diatom to these compounds. Diatoms represent an important aspect of the primary production community. They are a desirable food source over other members of the primary production community through storage of photosynthetically produced sugars in the form of lipids rather than starch. Therefore, many members of higher trophic levels selectively feed on diatoms when present with other members of the primary production community. This study examines the effects of 17beta-estradiol and 4-nonylphenol on the physiological development of the diatom species Melosira varians. Clearly, unicellular protists such as diatoms are not susceptible to these contaminants in a manner directly analogous to that expressed in vertebrates. However, estradiol and nonylphenol are lipophilic making them particularly effective in entering the diatom cell membrane. Melosira varians was selected because it commonly occurs in most freshwater environments and has been the subject of other toxicological studies. An adequate literature base also exists for evaluating results of this experiment. The species grows rapidly and is easy to maintain in culture. Comparing cell density, chl-a, and lipid content in control and exposed cultures allowed interpretation of how the species responded to varying compound concentrations. Results of this study revealed differences in responses to each compound. 17beta-estradiol appears to have no detrimental effect on M. varians, while 4-nonylphenol results in cell mortality with sufficient dosage. Similar results with 17beta-estradiol are reported for other autotrophic organism, but the 4-nonylphenol response is not as uniform in other photosynthetic groups. The use of a phytoplankton species as a test organism complements other investigations involving vertebrate models at or near the apex of the trophic hierarchy by considering effects at the base of the food web.


Subject(s)
Diatoms/drug effects , Estradiol/toxicity , Estrogens/toxicity , Phenols/toxicity , Water Pollutants, Chemical/toxicity , Chlorophyll/analysis , Chlorophyll A , Lipids/analysis , Population Density
SELECTION OF CITATIONS
SEARCH DETAIL
...