Influence of polystyrene microplastics on rotifer (Brachionus calyciflorus) growth, reproduction, and antioxidant responses

Most aquatic environments are suffering from microplastic pollution, which poses a threat to the physiological and ecological characteristics of aquatic animals. The phospholipid hydroperoxide glutathione peroxidase gene (PHGPx) has an important function in the antioxidative defense of organisms. Here, we revealed for the first time that the full-length cDNA of PHGPx in Brachionus calyciflorus was 817 bp long and contained a 512 bp open reading frame. B. calyciflorus was exposed to 0 (control), 1 × 104, 1 × 105, 1 × 106, and 1 × 107 particles mL−1 polystyrene (particle size: 1 µm). Specific growth rate (SGR); reproductive rate (R); superoxide dismutase (SOD), catalase (CAT), and PHGPx activities; manganese superoxide dismutase (MnSOD), copper and zinc superoxide dismutase (CuZnSOD), CAT, and PHGPx expression; and reactive oxygen species (ROS) levels were investigated. Our results showed that polystyrene enhanced ROS production. SGR, R, PHGPx activity, and PHGPx expression decreased with the increase in polystyrene concentrations. SOD and CAT activities and MnSOD, CuZnSOD, and CAT expression levels increased upon exposure to 1 × 104–1 × 106 particles mL−1 polystyrene but decreased under exposure to 1 × 107 particles mL−1 polystyrene. These results revealed that PHGPx, MnSOD, CuZnSOD, and CAT expression regulates antioxidant enzyme activities, which are involved in the PHGPx-associated antioxidant defense of rotifers in response to polystyrene.