Microplastic-Contaminated Feed Interferes with Antioxidant Enzyme and Lysozyme Gene Expression of Pacific White Shrimp (Litopenaeus vannamei) Leading to Hepatopancreas Damage and Increased Mortality

SIMPLE SUMMARY: Plastic waste in the marine environment can be degraded into microplastic particles that are smaller than 5 mm in diameter. Such microplastic particles can interfere with the effectors of the nonspecific immune system in crustaceans, effectively debilitating a major defense mechanism against infectious diseases. Pacific white shrimp (Litopenaeus vannamei) is one of the most important marine crustacean species with global presence in the aquaculture industry that is at high risk of being contaminated with microplastics due to its feeding habits and benthic food sources. Such contamination may increase the risk of adverse effects on shrimp health. Thus, this study aimed to investigate the effects of oral intake of microplastic in food on the nonspecific immune system gene expression of Pacific white shrimp. We demonstrated immunosuppression at the gene expression level and histological damage of the hepatopancreas in shrimp fed with microplastic-contaminated food, leading to higher mortality. Information from L. vannamei can be used as a model system for other marine decapods. The increased presence of microplastic pollution in the environment and food has the potential to affect shrimp fisheries and aquaculture in the future, as well as further destabilize marine ecosystems already exposed to the combined anthropogenic and climate changes. ABSTRACT: Microplastic pollution can interfere with aquatic animal health and nonspecific immunity, increasing the potential for pathogen infection in crustaceans. However, the long-term effects of microplastics on crustacean immunity are less understood, especially regarding their toxicity in Pacific white shrimp (Litopenaeus vannamei). Effects of high-density polyethylene microplastics (HDPE-MPs) in feed on the mortality rate, hepatopancreas, and nonspecific immune system gene expression of Pacific white shrimp are presented. The LC(50) at day 28 of HDPE-MP exposure was determined as 3.074% HDPE-MP in feed. A significant upregulation of the superoxide dismutase (SOD) and glutathione peroxidase (GPx) genes was observed in shrimp that were fed with 0.1 and 0.5% of HDPE-MP; then, they were downregulated significantly, except for the SOD gene expression of shrimp fed with 0.1% of HDPE-MP. The lysozyme (LYZ) gene was upregulated significantly in shrimp that were fed with 0.5, 1, and 3% HDPE-MP for 7 days and downregulated significantly in HDPE-receiving groups for at least 14 days. Significant histopathological changes in the hepatopancreas were observed in the treatment groups. The histopathological score of each lesion was correlated with the increase in HDPE-MP concentration. This study shows that the ingestion of HDPE microplastics can alter the expression of nonspecific immune system genes and damage the hepatopancreas in Pacific white shrimp.