ECOTOXICOLOGY: FISH
Ekman D. R., Skelton D. M., Davis J. M., Villeneuve D. L., Cavallin J. E., Schroeder A., Jensen K. M., Ankley G. T., Collette T. W. (2015): Metabolite profiling of fish skin mucus: a novel approach for minimally-invasive environmental exposure monitoring and surveillance. Environmental Science and Technology 49: 3091-3100.
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Abstract
The application of ‘omics tools to biologically based monitoring and surveillance of aquatic environments shows considerable promise for complementing chemical monitoring in ecological risk assessments. However, few of the current approaches offer the ability to sample ecologically relevant species (e.g., fish) in a way that produces minimal impact on the health of the organism(s) under study. In the current study we employ liquid chromatography tandem mass spectrometry (LC-MS/MS) to assess the potential for skin mucus-based metabolomics for minimally invasive sampling of the fathead minnow (FHM; Pimephales promelas). Using this approach we were able to detect 204 distinct metabolites in the FHM skin mucus metabolome representing a large number of metabolite classes. An analysis of the sex specificity of the skin mucus metabolome showed it to be highly sexually dimorphic with 72 of the detected metabolites showing a statistically significant bias with regard to sex. Finally, in a proof-of-concept fashion we report on the use of skin mucus-based metabolomics to assess exposures in male and female fathead minnows to an environmentally relevant concentration of bisphenol A, a nearly ubiquitous environmental contaminant and an established endocrine active chemical.
Mosley J. D., Ekman D. R., Cavallin J. E., Villeneuve D. L., Ankley G. T., Collette T. W. (2018): High‐resolution mass spectrometry of skin mucus for monitoring physiological impacts and contaminant biotransformation products in fathead minnows exposed to wastewater effluent. Environmental Toxicology and Chemistry 37: 788-796.
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High-resolution mass spectrometry is advantageous for monitoring physiological impacts and contaminant biotransformation products in fish exposed to complex wastewater effluent. We evaluated this technique using skin mucus from male and female fathead minnows (Pimephales promelas) exposed to control water or treated wastewater effluent at 5, 20, and 100% levels for 21 d, using an on-site, flow-through system providing real-time exposure. Both sex-specific and non-sex–specific responses were observed in the mucus metabolome, the latter suggesting the induction of general compensatory pathways for xenobiotic exposures. Altogether, 85 statistically significant treatment-dependent metabolite changes were observed out of the 310 total endogenous metabolites that were detected (156 of the 310 were annotated). Partial least squares-regression models revealed strong covariances between the mucus metabolomes and up-regulated hepatic messenger ribonucleic acid (mRNA) transcripts reported previously for these same fish. These regression models suggest that mucus metabolomic changes reflected, in part, processes by which the fish biotransformed xenobiotics in the effluent. In keeping with this observation, we detected a phase II transformation product of bisphenol A in the skin mucus of male fish. Collectively, these findings demonstrate the utility of mucus as a minimally invasive matrix for simultaneously assessing exposures and effects of environmentally relevant mixtures of contaminants.
Oliveira M., Tvarijonaviciute A., Trindade T., Soares A. M. V. M., Tort L., Teles M. (2018): Can non-invasive methods be used to assess effects of nanoparticles in fish? Ecological Indicators 95: 1118-1127.
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The use of less invasive methods to assess the biological effects of xenobiotics on aquatic species is currently a research priority. Fish skin mucus appears as a promising biological matrix, allowing the assessment of biochemical endpoints with the advantage of non-invasive sampling. This study aimed to compare the sensitivity of plasma and skin mucus matrices in a marine fish, Sparus aurata, after 24 and 96 h exposure to 0.5 and 50 μg.L−1 of 37 nm citrate coated gold nanoparticles (AuNP). Results showed a higher responsiveness of skin mucus, after 24 h exposure, in terms of total antioxidant capacity (TAC), as demonstrated by its increase for both concentrations when compared to the single increase, found in the 0.5 μg.L−1 condition in blood plasma. The total oxidative status levels (TOS) did not appear as promising in skin mucus under the tested conditions, presenting levels below the detection limit whereas in blood plasma TOS levels were quantifiable and significantly increased after 96 h. Esterase activity (EA) was decreased in skin mucus after 24 h exposure to 0.5 μg.L−1 AuNP, remaining unaltered in blood plasma. Cortisol, the main stress indicator in fishes, presented unaltered levels in both biological matrices and a positive correlation was found between cortisol and TAC. Overall, results support the use of skin mucus as a biological matrix and TAC and EA as potential biomarkers to monitor the effects of NP effects in fishes.
Montenegro D., Astudillo-García C., Hickey T., Lear G. (2020): A non-invasive method to monitor marine pollution from bacterial DNA present in fish skin mucus. Environmental Pollution 263: 114438.
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Marine coastal contamination caused by human activity is a major issue worldwide. The implementation of effective pollution monitoring programs, especially in coastal areas, is important and urgent. The use of biological, physiological, or biochemical measurements to monitor the impacts of pollution has garnered increasing interest, particularly for the development of new non-invasive tools to assess water pollution. Fish skin mucus is in direct contact with the marine environment, making it a favourable microenvironment for the formation of biofilm bacterial communities. In this study, we developed a non-invasive technique, sampling fish skin mucus to determine and analyse bacterial community composition using next-generation sequencing. We hypothesised that bacterial communities associated with the skin mucus of a common harbour benthic blennioid triplefin fish, Forsterygion capito, would reflect conditions of different marine environments. We detected clear differences in bacterial community alpha-diversity between contaminated and reference sites. Beta-diversity analysis also revealed differences in the bacterial community structure of the skin mucus of fish inhabiting different geographical areas. The relative abundance of different bacterial orders varied among sites, as determined by linear discriminant analysis (LDA) and effect size (LEfSe) analyses. The observed variation in bacterial community compositions correlated more strongly with variation in hydrocarbons than to various metal concentrations. Using advanced DNA sequencing technologies, we have developed a novel non-invasive, low-cost and effective tool to monitor the impacts of pollution through analysis of the bacterial communities associated with fish skin mucus.
Yong M. M. H., Leistenschneider C., Miranda J. A., Paler M. K., Legaspi C., Germanov E., Araujo G., Burkhardt-Holm P., Erni-Cassola G. (2021): Microplastics in fecal samples of whale sharks (Rhincodon typus) and from surface water in the Philippines. Microplastics and Nanoplastics 1: 17.
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Marine plastic abundance has increased over the past 60 years and microplastics (< 5 mm) constitute a primary component of such litter. Filter-feeding megafauna, such as the whale shark, might be particularly affected by microplastic pollution as their feeding mode requires filtration of up to thousands of cubic meters of water. In addition, the habitat range of whale sharks intersects with several recognized microplastic pollution hotspots, among which is the Coral Triangle. Direct evidence for microplastic ingestion in whale sharks however, has not yet been presented. Here we show that whale shark scat collected in the Philippines from 2012 to 2019 contained a mean of 2.8 microplastics g− 1. Contrary to our expectations, the microplastic concentration in the scat remained consistent from 2012 to 2019. Water samples from the study site in 2019 indicated that the local microplastic pollution (5.83 particles m− 3) was higher than in surface waters in other whale shark habitats, but well below other pollution hot-spots found in Southeast Asia and China (range: 100–4100 particles m− 3). With the predicted growth in plastic use, leading to increased plastic marine pollution, whale sharks are expected to become more exposed to this form of pollution. To what extent microplastic ingestion impacts the overall health status of this endangered species remains an open question.
Tomasello D. L., Wlodkowic D. (2022): Noninvasive electrophysiology: Emerging prospects in aquatic neurotoxicity testing. Environmental Science & Technology 56: 4788-4794.
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The significance of neurotoxicological risks associated with anthropogenic pollution is gaining increasing recognition worldwide. In this regard, perturbations in behavioral traits upon exposure to environmentally relevant concentrations of neurotoxic and neuro-modulating contaminants have been linked to diminished ecological fitness of many aquatic species. Despite an increasing interest in behavioral testing in aquatic ecotoxicology there is, however, a notable gap in understanding of the neurophysiological foundations responsible for the altered behavioral phenotypes. One of the canonical approaches to explain the mechanisms of neuro-behavioral changes is functional analysis of neuronal transmission. In aquatic animals it requires, however, invasive, complex, and time-consuming electrophysiology techniques. In this perspective, we highlight emerging prospects of noninvasive, in situ electrophysiology based on multielectrode arrays (MEAs). This technology has only recently been pioneered for the detection and analysis of transient electrical signals in the central nervous system of small model organisms such as zebrafish. The analysis resembles electroencephalography (EEG) applications and provides an appealing strategy for mechanistic explorative studies as well as routine neurotoxicity risk assessment. We outline the prospective future applications and existing challenges of this emerging analytical strategy that is poised to bring new vistas for aquatic ecotoxicology such as greater mechanistic understanding of eco-neurotoxicity and thus more robust risk assessment protocols.