Species-Specific Effects of Microplastics On Juvenile Fishes

Microplastics contamination have been extensively reported in aquatic ecosystem and organisms. It is wildly acknowledged that the ingestion, accumulation and elimination of microplastics in fishes are species-specific, which mainly depending on the feeding behavior. This study aims to investigate the effects of microplastics on the morphology and inflammatory response in intestines of fishes with different feeding types. Largemouth bass (carnivorous fish), grass carp (herbivorous fish) and Jian carp (omnivorous fish) were used as organism model. The contributing concentration and size of microplastics are explored as well as the response time and legacy effect in fishes. Two different sizes of polystyrene microplastics (8 μm and 80 nm) were set at three concentrations. And samples were analyzed at different exposure times and depuration times. Histological analysis indicated that multiple abnormalities in intestines are presented in three species fishes after acute exposure microplastics. The mRNA abundance of immune-related genes in the intestine tissues of fishes were significantly induced or restrained. There were differential expressions of genes coping with differential sizes and concentrations of microplastics exposure in different fishes. The reason for the difference effects of microplastics on fishes was still unclear but could be due to the difference in the structure and function of the digestive system. These results provide a theoretical basis to further analysis of the mechanism of fish intestinal pathology caused by microplastics.

Interactive Effects of Microplastics and Tetracycline on Bioaccumulation and Biochemical Status in Jian Carp (Cyprinus carpio var. Jian)

Microplastics (MPs) and tetracycline (TC) are severe emerging pollutants in the aquatic environment. But there is a lack of research to investigate the interactive effects of MPs and TC in vivo. This study used Jian carp (Cyprinus carpio var. Jian) as the model organism to explore the bioaccumulation and biochemical status when exposed to MPs and TC, alone and combined. The accumulation of TC and MPs in intestine, variation of enzyme activities in intestine, and expression of immune-related genes in muscle were evaluated. Our results found the bioaccumulation of MPs was not affected by TC, but the presence of MPs would change the content of TC within 48 h. The superoxide dismutase (SOD) and lactate dehydrogenase (LDH) activity showed that TC-MP combined exposure could reduce oxidative damage to Jian carps compared to MP exposure alone. The integrated biomarker response (IBR) index showed that SOD activity was sensitive to TC-MP exposure. In addition, co-exposure to MPs and TC could alleviate the overexpression of interleukin 1 beta (IL-1β), interleukin 10 (IL-10), transforming growth factor beta (TGF-β), and toll like receptor 2 (TLR-2) induced by TC in muscles. TLR-2 gene has the potential to be the candidate gene reflecting the injury of TC exposure. In conclusion, it is inferred that co-exposure may reduce the toxicity of individual exposure in the living organisms. This study provides essential information for the risk assessment of pollution with MPs and TC, individually and combined, as well as a foundation to investigate the interactive effects of MPs and antibiotics on aquatic ecosystems.