Plastic pollution
can pose a threat to birds. Yet, little
is known
about the sublethal effects of ingested microplastics (MP), and the
effects of MP < 1 mm in birds remain unknown. This study therefore
aimed at evaluating the toxicity of environmentally relevant polypropylene
and polyethylene particles collected in the Norwegian coast in growing
Japanese quail (Coturnix japonica).
Birds were orally exposed to 600 mg MP over 5 weeks, covering small
(<125 μm) and large (3 mm) MP, both separately and in a mixture.
We evaluated multiple sublethal endpoints in quail, including oxidative
stress, cytokine levels, blood-biochemical parameters, and reproductive
hormones in blood, as well as body mass. Exposure to small MP significantly
induced the activities of the antioxidant enzymes catalase, glutathione-S-transferase,
and glutathione peroxidase. Exposure to large MP increased the levels
of aspartate aminotransferase (liver parameter) and decreased 17β-estradiol
levels in females. Body mass was not directly affected by MP ingestion;
however, quail exposed to small MP and a mixture of large and small
MP had a different growth rate compared to control quail. Our study
used similar levels of MP as ingested by wild birds and demonstrated
size-dependent effects of MP that can result in sublethal effects
in avifauna.
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