A Holistic Assessment of Polyethylene Fiber Ingestion in Larval and Juvenile Japanese Medaka Fish

Abstract

Microplastic pollution is of public concern for global environmental health, aquaculture, and fisheries. Toxicity studies have shown that microplastic ingestion may cause intestinal damage, microbiota dysbiosis, and disturb the lipid and energy metabolism in fish. To determine the impact of environmentally relevant, chronic, low dose microplastic fibers on fish health, medaka larvae, and juveniles were exposed to five concentrations of polyethylene (PE) fibers for 21 days through the feed. Fish growth and condition were assessed to determine the overall impact on fish health. To identify impaired energy intake, the gastrointestinal tract (GIT) integrity was evaluated at the molecular and cellular levels. Microbiota analysis was performed by comparing the top seven most abundant phyla present in both larval and juvenile fish exposed to 0, 1.5, and 3 PE fibers/fish/day. A shift in the phyla Proteobacteria and Bacteroidetes were observed. Larval samples demonstrated decreased proteobacteria abundance, while juvenile samples displayed an increase in abundance. Relative gene expression of key digestive genes from GIT tissue was quantified using real time-quantitative polymerase chain reaction. An effect on digestive gene expression potentially affecting nutrient absorption and antioxidant production was indicated via a significant decrease of solute carrier family 6 member 6 expression in larvae exposed to 6 fibers/fish/day. No significant molecular changes were observed in juvenile GIT tissue, although a non-monotonous dose-response was observed. GIT morphology was analyzed using histomorphological observations of the GIT mucus and cell types. No significant impairment of the GIT epithelial layers was observed in larvae or juveniles. To assess growth and condition, Fulton’s condition factor was measured. No differences were observed in larval or juvenile growth. Comparisons of different developmental stages allowed for identifying vulnerable developmental stages for microplastic exposure; larvae were more susceptible to molecular changes, while shifts in juvenile microbial communities were similar to changes reported post-polystyrene microplastic sphere exposure. This study is one of the first to provide toxicological data on the risk of PE fiber ingestion during fish development stages. Results indicate no imminent threat to fish condition at current measured environmental levels of microplastics; however, close monitoring of vital spawning grounds for commercially important fishes is recommended.

Developmental Polyethylene Microplastic Fiber Exposure Entails Subtle Reproductive Impacts in Juvenile Japanese Medaka (Oryzias latipes)

“…At the completion of breeding all individuals were euthanized using hypothermic shock and allocated to the necessary endpoints. The polyethylene fiber uptake was validated in a short‐term and long‐term retention assessment (DiBona et al, 2021).…”

“…Microplastic fiber preparation. The exposure materials and methods for the present study were previously published in DiBona et al (2021). Briefly, Lumat USA provided blue multifilament polyethylene yarn, which was confirmed to be an 86% match to low-density polyethylene using a Fourier transform infrared-attenuated total reflectance device (Thermo Fisher Scientific).…”

“…Juvenile exposure. The exposure methods were previously published in DiBona et al (2021). Briefly, juvenile O. latipes were exposed to five concentrations of 400-µm-long polyethylene fibers through 0.1 g of ground dry larval feed once daily for a consecutive 21-day period.…”

The effect of environmental stressors on growth in fish and its endocrine control

“…However, no relations with food intake were found in that work. On the other hand, the ingestion of polyethylene microplastics by larvae and juveniles of medaka ( Oryzias latipes ) does not affect the expression of molecular markers involved in glucose metabolism, energy homeostasis, weight gain, and proteolysis (ISN, GLP, PYY, and TRP) ( 333 ).…”

Microplastics as Contaminants in Water Bodies and Their Threat to the Aquatic Animals: A Mini-Review

“…In addition, photoaged MPs down-regulated genes including cd 36 , mttp , and dgat2 , which are associated with triglyceride resynthesis and transportation to cause lipid malabsorption and growth inhibition in zebrafish larvae [ 81 ]. The MPs could accumulate total bile acids and change the nutrient metabolism in Perca flavescens [ 82 ], impair digestion and nutrient absorption functions in Oreochromis urolepis [ 83 ], and influence the digestive gene expression in Oryzias latipes , affecting nutrient absorption and antioxidant production [ 84 ].…”