Sublethal Impacts of Polyethylene Microplastics on Freshwater Amphipods: Genotoxic and Metabolic Responses in Echinogammarus veneris and Cryptorchestia garbinii (Crustacea, Amphipoda)

Microplastic (MP) contamination represents a global threat to aquatic ecosystems, yet its biological effects remain poorly understood. This study investigates the short-term impacts of polyethylene (PE) microparticles on two amphipod species: the semi-terrestrial Cryptorchestia garbinii and the aquatic Echinogammarus veneris. Amphipods are exposed to MPs both in water and through dietary intake. After 24 h, C. garbinii ingested an average of 9.6 ± 1.2 particles per individual, while E. veneris ingested 12.5 ± 2.8 particles, confirming an active uptake of microplastics. The mean particle size decreased from ≌50 µm in the food tablets to 18–25 µm in the digestive tract, suggesting fragmentation during digestion and highlighting the ecological role of amphipods in generating smaller, potentially more bioavailable particles. Both species exhibited a marked increase in DNA damage, together with variations in energy-reserve allocation (glucose, glycogen, and lipids) consistent with acute metabolic stress. To our knowledge, this represents the first evidence of genotoxicity ever reported in C. garbinii, expanding current understanding of the biological responses of amphipods to plastic pollution. These findings highlight the vulnerability of detritivore species to MPs exposure and, given their role in nutrient cycling, emphasize the need for further research on the ecological implications of MPs contamination.