Resolving mechanisms of toxicity while pursuing ecotoxicological relevance?

Laboratory of Molecular Aquatic Toxicology, Division of Environmental Sciences and Policy, Nicholas School of the Environment and Earth Sciences, Duke University Durham, NC 277-8-0328, USA.
Marine Pollution Bulletin (Impact Factor: 2.99). 02/2005; 51(8-12):635-48. DOI: 10.1016/j.marpolbul.2005.07.020
Source: PubMed


In this age of modern biology, aquatic toxicological research has pursued mechanisms of action of toxicants. This has provided potential tools for ecotoxicologic investigations. However, problems of biocomplexity and issues at higher levels of biological organization remain a challenge. In the 1980s and 1990s and continuing to a lesser extent today, organisms residing in highly contaminated field sites or exposed in the laboratory to calibrated concentrations of individual compounds were carefully analyzed for their responses to priority pollutants. Correlation of biochemical and structural analyses in cultured cells and tissues, as well as the in vivo exposures led to the production and application of biomarkers of exposure and effect and to our awareness of genotoxicity and its chronic manifestations, such as neoplasms, in wild fishes. To gain acceptance of these findings in the greater environmental toxicology community, "validation of the model" versus other, better-established often rodent models, was necessary and became a major focus. Resultant biomarkers were applied to heavily contaminated and reference field sites as part of effects assessment and with investigations following large-scale disasters such as oil spills or industrial accidents. Over the past 15 years, in the laboratory, small aquarium fish models such as medaka (Oryzias latipes), zebrafish (Danio rerio), platyfish (Xiphophorus species), fathead minnow (Pimephales promelas), and sheepshead minnow (Cyprinodon variegatus) were increasingly used establishing mechanisms of toxicants. Today, the same organisms provide reliable information at higher levels of biological organization relevant to ecotoxicology. We review studies resolving mechanisms of toxicity and discuss ways to address biocomplexity, mixtures of contaminants, and the need to relate individual level responses to populations and communities.

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Available from: David C. Volz, Sep 12, 2014
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    • "Recently, small fishes are increasingly taken as model species for physiological and biochemical studies (Hinton et al., 2005). The marine medaka Oryzias melastigma, which is a counterpart of the freshwater medaka O. latipes with genome data available, has been advocated to be a saltwater fish model for marine environmental research and ecotoxicological studies (Fang et al., 2012; Wu et al., 2012). "
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    ABSTRACT: This study aimed to investigate temperature effect on physiological and biochemical responses of the marine medaka Oryzias melastigma larvae. The fish were subjected to a stepwise temperature change at a rate of 1 °C/h increasing or decreasing from 25 °C (the control) to six target temperatures (12, 13, 15, 20, 28 and 32 °C) respectively, followed by a 7-day thermal acclimation at each target temperature. The fish were fed ad libitum during the experiment. The results showed that cumulative mortalities were significantly increased at low temperatures (12 and 13 °C) and at the highest temperature (32 °C). For the survivors, their growth profile closely followed the left-skewed ‘thermal performance curve′. Routine oxygen consumption rates of fish larvae were significantly elevated at 32 °C but suppressed at 13 and 15 °C (due to a high mortality, larvae from 12 °C were not examined). Levels of heat shock proteins and activities of malate dehydrogenase and lactate dehydrogenase were also measured in fish larvae exposed at 15, 25 and 32 °C. The activities of both enzymes were significantly increased at both 15 and 32 °C, where the fish larvae probably suffered from thermal discomfort and increased anaerobic components so as to compensate the mismatch of energy demand and supply at these thermal extremes. Coincidently, heat shock proteins were also up-regulated at both 15 and 32 °C, enabling cellular protection. Moreover, the critical thermal maxima and minima of fish larvae increased significantly with increasing acclimation temperature, implying that the fish could develop some degrees of thermal tolerance through temperature acclimation.
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    • "Substantial advances have been made in recent years regarding the complex molecular and cellular mechanisms involved in physiological responses to pollutants. Still, determining the broad population-and community-level consequences is necessary to establish the ecological relevance of pollution (Hinton et al. 2005). In the aftermath of the Macondo blowout, the most comprehensive ecotoxicological studies must consider both broad and focused perspectives (Fodrie et al. 2014). "
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    ABSTRACT: In addition to external oiling, marine oil spills may affect vertebrate animals through degradation of habitat; alterations in food web structure; and contamination of resources by toxic compounds, including polycyclic aromatic hydrocarbons. These processes are not well understood for vertebrates breeding and foraging in terrestrial ecosystems affected by oil, such as coastal marshes that were heavily oiled following the 2010 Macondo oil spill. Here, we review what is known about the ecological and physiological effects of oil exposure on vertebrates in general. We then apply these concepts to salt-marsh vertebrates, with special reference to our ongoing monitoring of impacts and recovery in the seaside sparrow (Ammodramus maritimus) and marsh rice rat (Oryzomys palustris) in Louisiana following the Macondo spill.
    Full-text · Article · Sep 2014 · BioScience
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    • "In the recent decade, there is a trend of using small size freshwater fish as the model animals for ecotoxicology research, such as zebrafish, Japanese medaka, and fathead minnow (Pimephales promelas) (Hinton et al., 2005; Ankley et al., 2009; Chen et al., 2011a). However, these commonly used freshwater fish models are not suitable for assessing the environmental stress in the estuarine/marine environment. "
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    ABSTRACT: We assessed the effects of 17α-ethinylestradiol (EE2) on spawning and reproductive behavior of the brackish medaka Oryzias melastigma at environmental concentrations. Breeding pairs were exposed to EE2 at either lower concentrations (0, 1, and 10ng/L) or higher concentrations (0, 50, and 100ng/L) for 14days. Swimming performance and reproductive behavior (following, dancing, and copulation) of the males were analyzed at the end of exposure. Additionally, gonad histology was conducted in the males in the higher EE2 experiment. We found that spawning was significantly inhibited in the 50-100ng/L EE2 groups. Swimming performance was not affected in all groups. Dancing and copulation were significantly suppressed in the 50-100ng/L groups. No effect was observed in testis histology in the 50-100ng/L groups. Our data suggests that reproductive behavior of O. melastigma can be utilized as a behavioral endpoint for ecotoxicology studies of endocrine disruptors in estuarine/marine environments.
    Full-text · Article · Apr 2014 · Marine Pollution Bulletin
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