Chronic dietary exposure to polystyrene microplastics in maturing Japanese medaka (Oryzias latipes)
Introduction
Concern over risks from microplastics (MPs) increases as the enormity of their quantity and global distribution in marine and freshwater ecosystems is realized (Browne et al., 2011; Eerkes-Medrano et al., 2015; Van Sebille et al., 2015). MPs are generally regarded as <5 mm in diameter (Arthur et al., 2009). In an extensive review, Triebskorn et al. (2019) highlighted the importance of particles <20 μm and their high relevance for freshwater biota. The dominant type of MPs in biota are polyester fibers with polystyrene (PS) particles (e.g., fragments, spheres) being the second most common after polyethylene (PE) (de Sá et al., 2018; Mishra and Rath, 2019). After fibers, spherical MPs are an abundant shape (de Sá et al., 2018).
MPs must be considered as environmentally relevant mixtures. Additives are integrated into plastics during manufacturing as stabilizers, flame retardants, pigments, and fillers (Lithner et al., 2011). Most additives, such as bisphenol A (BPA) and phthalates, are bound to the polymers by weak non-covalent forces, allowing them to leach into surrounding media over time (Halden, 2010). Other polymerization impurities (e.g., oligomers, catalyst remnants, polymerization solvents, metals) may also be present and migrate from plastic into other contact media such as water and food (Lithner et al., 2011) where they can be taken up and bioaccumulate in organisms (Oehlmann et al., 2009).
To date, marine systems have been the focus of MP investigations, both in quantification in water and sediment as well as occurrences of MPs in biota (Blettler et al., 2018). Due to their intermediate and apical positions in aquatic food webs, fish may ingest MPs directly and/or consume them when feeding on other organisms (de Sá et al., 2015; Lusher et al., 2013; Wright et al., 2013). Once ingested, important effects such as false satiation, gut blockage, and altered gut function may result leading toward diminished nutrition (Jovanović, 2017; Wright et al., 2013). Juvenile gobies (Pomatoschistus microps) fed polyethylene (PE) MPs had reductions in number of consumed prey items (de Sá et al., 2015). Cong et al. (2019) fed marine medaka (Oryzias melastigma) 10 μm PS MPs and observed diminished growth (i.e., individual body length and weight).
Japanese medaka (Oryzias latipes), a laboratory aquarium model fish, mature rapidly (8–12 wks) (Lawrence et al., 2012), facilitating the analysis of chronic endpoints. They are agastric teleosts with three intestinal segments with distinct functions (Aghaallaei et al., 2016). Female medaka produce eggs daily and embryos have well-documented developmental stages (Iwamatsu, 2004). Additionally, their small body size makes it possible to embed intact individuals for histologic sectioning, providing information on all internal organs in a few sections, saving time and cost (Kinoshita et al., 2009; Shima and Mitani, 2004).
Both outbred orange red (OR) and see-through medaka were used to determine MP translocation. OR medaka were utilized to test impacts of ingestion of commercially available 10 um PS fluorescent microspheres. Our objective was to determine whether chronic dietary exposure impacted medaka over multiple life stages during which rapid growth and sexual differentiation occurred. We assessed whole animal and organ and tissue level responses with high-resolution microscopy techniques.
Section snippets
Medaka colonies
Orange-red (OR) and see-through Quintet (Strain ID: MT829) medaka (Oryzias latipes) breeding colonies were housed in a recirculating aquatic system (Pentair Aquatic Eco-Systems, Apopka, FL) at Duke University. Housing conditions were 24 °C with pH 7.2–7.6, and a 14:10 light:dark cycle. The breeding colony was fed Otohime β1 commercial dry diet (200−360 μm, Pentair Aquatic Eco-Systems) 3 times per day. This was supplemented with Artemia spp. nauplii twice daily (90 % Great Lakes Strain, Pentair
Medaka condition, growth, and reproduction
MPs were absent in control fish. Physical deformities were also absent during maturation and no mortalities resulted. Growth (i.e., standard length, weight, and K) did not differ between treatment groups (Fig. S4). There were no sex differences in these parameters in the last weeks of exposure. The percent of ingested MPs that were egested was 0.5–2 % per day. Fish in low exposure group egested proportionally more of the ingested MPs than the other exposure groups (p < 0.001; Fig. S5). Fish in
Discussion
Chronic dietary exposure to polystyrene MPs targeted whole animal responses over multiple life stages during which rapid growth and sexual differentiation occur. Extension of observations using high resolution microscopy at organ and tissue levels revealed definitive morphological responses not evident in whole animal observations.
Using repeated and highly focused detection methods, preliminary tests determined that the 10 μm PS MPs used in the present study remained in gut lumen and were
Conclusions
Our investigation of chronic dietary exposure to MPs found responses in gill, structural damage in gut, impacts on kidney and spleen, and dose-dependent decrease in egg production. Because MPs remained in gut lumen, alterations in other internal organs were likely due to additives. While MPs did not inhibit nutrition and growth, they negatively affected innate defense mechanisms and damaged cells, thereby facilitating passage of additives, or possibly pathogens, from gut lumen into the
CRediT authorship contribution statement
Mei Zhu: Conceptualization, Methodology, Formal analysis, Investigation, Writing - original draft, Writing - review & editing, Visualization. Melissa Chernick: Conceptualization, Methodology, Validation, Formal analysis, Resources, Data curation, Writing - review & editing, Visualization. Daniel Rittschof: Conceptualization, Resources, Writing - review & editing, Supervision, Funding acquisition. David E. Hinton: Conceptualization, Methodology, Validation, Resources, Writing - review & editing,
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by the Oak Foundation. Sample preparation and imaging for scanning electron microscopy was performed at the Duke University Shared Materials Instrumentation Facility (SMIF), a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), which is supported by the National Science Foundation (Grant ECCS-1542015) as part of the National Nanotechnology Coordinated Infrastructure (NNCI). We would like to thank J. Mac Law at NC State University College of
References (71)
- et al.
Freshwater plastic pollution: recognizing research biases and identifying knowledge gaps
Water Res.
(2018) - et al.
Dietary CdSe/ZnS quantum dot exposure in estuarine fish: bioavailability, oxidative stress responses, reproduction, and maternal transfer
Aquat. Toxicol.
(2014) - et al.
Digestive system
- et al.
Ingestion, egestion and post-exposure effects of polystyrene microspheres on marine medaka (Oryzias melastigma)
Chemosphere
(2019) - et al.
Effects of microplastics on juveniles of the common goby (Pomatoschistus microps): confusion with prey, reduction of the predatory performance and efficiency, and possible influence of developmental conditions
Environ. Pollut.
(2015) - et al.
Studies of the effects of microplastics on aquatic organisms: What do we know and where should we focus our efforts in the future?
Sci. Total Environ.
(2018) - et al.
Microplastics in freshwater systems: a review of the emerging threats, identification of knowledge gaps and prioritisation of research needs
Water Res.
(2015) - et al.
Occurrence and effects of plastic additives on marine environments and organisms: a review
Chemosphere
(2017) - et al.
Medaka fish, Oryzias latipes, as a model for human obesity-related glomerulopathy
Biochem. Biophys. Res. Commun.
(2013) Stages of normal development in the medaka Oryzias latipes
Mech. Dev.
(2004)
Effects of virgin microplastics on goldfish (Carassius auratus)
Chemosphere
Polystyrene microplastics induce microbiota dysbiosis and inflammation in the gut of adult zebrafish
Environ. Pollut.
Virgin microplastics are not causing imminent harm to fish after dietary exposure
Mar. Pollut. Bull.
A high-performance protocol for extraction of microplastics in fish
Sci. Total Environ.
Biomarker responses in zebrafish (Danio rerio) larvae exposed to pristine low-density polyethylene fragments
Environ. Pollut.
Estrogenic endocrine disrupting chemicals in fish
Microplastic particles cause intestinal damage and other adverse effects in zebrafish Danio rerio and nematode Caenorhabditis elegans
Sci. Total Environ.
Comparison of six digestion methods on fluorescent intensity and morphology of the fluorescent polystyrene beads
Mar. Pollut. Bull.
Mucins in the mucosal barrier to infection
Mucosal Immunol.
Environmental and health hazard ranking and assessment of plastic polymers based on chemical composition
Sci. Total Environ.
Occurrence of microplastics in the gastrointestinal tract of pelagic and demersal fish from the English Channel
Mar. Pollut. Bull.
The effects of phthalates in the cardiovascular and reproductive systems: a review
Environ. Int.
Marine microfiber pollution: a review on present status and future challenges
Mar. Pollut. Bull.
Capture, swallowing, and egestion of microplastics by a planktivorous juvenile fish
Environ. Pollut.
Intestinal alterations in European sea bass Dicentrarchus labrax (Linnaeus, 1758) exposed to microplastics: preliminary results
Environ. Pollut.
Overview of mucosal structure and function in teleost fishes
Early warning signs of endocrine disruption in adult fish from the ingestion of polyethylene with and without sorbed chemical pollutants from the marine environment
Sci. Total Environ.
Chronic toxicity of nonylphenol and ethinylestradiol: haematological and histopathological effects in juvenile Common carp (Cyprinus carpio)
Aquat. Toxicol.
Medaka as a research organism: past, present and future
Mech. Dev.
Challenge with 17α-ethinylestradiol (EE2) during early development persistently impairs growth, differentiation, and local expression of IGF-I and IGF-II in immune organs of tilapia
Fish Shellfish Immunol.
Environmental impacts on fish mucosa
Relevance of nano- and microplastics for freshwater ecosystems: a critical review
Trac Trends Anal. Chem.
The renin-angiotensin-aldosterone system: a specific target for hypertension management
Am. J. Hypertens.
Morphological diversity of the gastrointestinal tract in fishes
The physical impacts of microplastics on marine organisms: a review
Environ. Pollut.
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