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Exposure of the amphipod Hyalella azteca to microplastics. A study on subtoxic responses and particle biofragmentation
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Scientists exposed freshwater amphipods (Hyalella azteca) to polystyrene microplastics and observed subtle but measurable effects on the animals' behavior and biology even at concentrations below those causing visible harm. Importantly, the amphipods physically broke down the microplastics into much smaller fragments through ingestion and digestion. The study highlights that animals in the environment may be actively generating nanoplastics from microplastics, accelerating the fragmentation of plastic pollution.
Microplastics are widespread pollutants in the environment and are considered a global pollution problem. Microplastics mostly originate from larger plastics and due to environmental conditions are undergoing constant fragmentation processes. It is important to understand the fragmentation pathways, since they play a key role in the fate of the particles, and also directly influence toxicity. Amphipods are potential inducers of plastic debris fragmentation. Here, Hyalella azteca was exposed to different concentrations (540, 2700, 5400 items/L) of 24.5 µm polystyrene microplastics (PS-MP) for 7 days. After exposure, oxidative stress, particle size reduction, and mortality were checked. No significant mortality was seen in any of the treatments, although changes were recorded in all enzymatic biomarkers analyzed. It was observed that throughout the ingestion and egestion of PS-MP by H. azteca, particles underwent intense fragmentation, presenting a final size up to 25.3% smaller than the initial size. The fragmentation over time (24, 72, 120, 168 h) was verified and the results showed a constant reduction in average particle size indicating that H. azteca are able to induce PS-MP fragmentation. This process may facilitate bioaccumulation and trophic particle transfer.
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The Toxicity of Poly(acrylonitrile-styrene–butadiene) Microplastics toward Hyalella azteca Is Associated with Biofragmentation and Oxidative Stress
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Researchers studied how the freshwater crustacean Hyalella azteca interacts with ABS microplastics, a common plastic used in electronics and automotive parts. They found that these small organisms can physically fragment the plastic particles into even smaller pieces, with pristine particles breaking down more than aged ones, and that exposure triggered measurable oxidative stress responses. The study highlights how biological processes in aquatic environments can accelerate microplastic fragmentation and how even common industrial plastics may pose ecological risks.
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Researchers exposed freshwater amphipods (Gammarus pulex) to polymethylmethacrylate nanoplastics and assessed effects on swimming behavior and gut microbiome composition. They found that nanoplastic exposure altered the animals' movement patterns and shifted the microbial communities in their digestive systems. The study suggests that even nanoscale plastic particles can affect the behavior and internal biology of important freshwater invertebrates.
Rapid fragmentation of microplastics by the freshwater amphipod Gammarus duebeni (Lillj.)
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Researchers discovered that the freshwater amphipod Gammarus duebeni can rapidly break down polyethylene microplastics into smaller fragments, including nanoplastics, during its feeding process. The fragmentation was closely linked to feeding behavior, with more and smaller fragments produced when food was present during depuration. The study highlights that aquatic organisms may play a previously underestimated role in determining the environmental fate of microplastics by accelerating their breakdown into even smaller particles.
Sublethal Impacts of Polyethylene Microplastics on Freshwater Amphipods: Genotoxic and Metabolic Responses in Echinogammarus veneris and Cryptorchestia garbinii (Crustacea, Amphipoda)
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Researchers exposed two freshwater amphipod species to polyethylene microparticles for 24 hours, finding active particle ingestion with fragmentation in digestive tracts, genotoxic responses measured by comet assay, and metabolic changes including elevated lactate suggesting energy metabolism disruption.
Responses of Hyalella azteca to acute and chronic microplastic exposures
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Researchers exposed the freshwater amphipod Hyalella azteca to polyethylene microplastics in both short-term and long-term laboratory tests. They found that chronic exposure over 10 days to high concentrations of the smallest microplastic particles reduced survival and reproduction. The study provides some of the first data on how microplastics affect freshwater invertebrates over extended periods, highlighting the importance of particle size and exposure duration.
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