Effect of Polystyrene Microplastic Exposure on Individual, Tissue, and Gene Expression in Juvenile Crucian Carp (Carassius auratus)

Exposure to an environment containing microplastics can cause adverse effects on creatures through respiratory and digestive systems. In this paper, 50–500 μm polystyrene microplastics (exposure concentrations were 200 μg/L, 800 μg/L, and 3200 μg/L concentrations) were selected to study the distribution of polystyrene microplastics (PS-MPs) and the effects on the growth, development, tissue damage and gene expression of crucian carp juveniles. The results showed that PS-MPs were enriched in the intestinal tract (GIT) and gill tissue of crucian carp, and the average number of PS-MPs was between 0 to 2.33 items per individual. It was found that the average number of MPs in the intestine was more than in the gills, and it was independent of the PS-MP concentration. However, the specific gravity of PS-MPs in excreta was concentration-dependent. In addition, it was found that the exposure of the medium concentration group promoted the weight of the crucian carp larvae, inhibited the growth rate, and reduced the weight in the low and high concentration groups. The histopathological results indicated that the intestinal, gill, brain, and liver tissues all showed different degrees of damage, and the higher the concentration of PS-MPs, the more severe damage to the tissue cells. This experiment evaluated 15 genes in three treatments, which found that PS-MPs had different effects on gene expression in the liver, intestine, and gill tissues, and the tested genes were involved in different response pathways associated with virulence.