Embryotoxic effects of polystyrene microplastics in zebrafish (Danio rerio)

Aware of the serious threat that plastic represents to the environment and to living organisms, the international scientific community has, over the last decade, focused the attention on the toxicological effects that micro and nanoplastics exert mainly on aquatic organisms. The aim of this study is to investigate the effects of polystyrene (PS) microplastics (MPs) on embryos and early life stages of zebrafish Danio rerioby performing a fish embryo toxicity test (FET). Zebrafish embryos were exposed to 200 particles/mL of 10 µm PS-MPs for 144 h post fertilization (hpf). The concentration was chosen in accordance with previous laboratory studies using zebafish adult and embryos. After specific extraction of samples, according to a patent for industrial invention to the Italian Ministry of Economic Development number no. 102018000003337, Microscopic (Zeiss) and Fourier transform infrared spectroscopy (FTIR) (Perkin Elmer) identification methods were applied for MP detection in zebrafish larvae. The results obtained showed that PS-MPs were accumulated on the surface of egg chorions and were able to cause hatching retardation, morphological abnormalities including tail and spinal column deformity, oedema and blood pooling. Moreover, at 144 hpf, the molecular analysis of gene expression of the genes involved in the anti-oxidant detoxification systems (cytochrome P450-CYP and Glutathione-S-transferase-GST) and oxidative stress response (catalase-CAT and superoxide dismutase-SOD) highlighted a clear trend of transcription up-regulation for all the selected genes in response to PS-MPs exposure. Therefore, according to the results obtained and previous literature, it is possible to affirm that the environmentally relevant concentrations of microplastic particles affect larval fish ecology and that embryo-larval stages are more sensitive than adult forms, thus representing a direct threat to fish populations and marine biodiversity.