Chronic exposure to high-density polyethylene microplastic through feeding alters the nutrient metabolism of juvenile yellow perch (Perca flavescens)

Microplastics are emergent contaminants threatening aquatic organisms including aquacultured fish.This study investigated the effects of high-density polyethylene(HDPE,100 to 125 mm)on yellow perch(Perca flavescens)based on integrative evaluation including growth performance,nutritional status,nutrient metabolism,fish health,and gut microbial community.Five test diets(0,1,2,4,or 8 g HDPE/100 g diet)containing 41%protein and 10.5%lipid were fed to juvenile perch(average body weight,25.9±0.2 g;n=15)at a feeding rate of 1.5%to 2.0%body weight daily.The feeding trial was conducted in a flow-through water system for 9 wk with 3 tanks per treatment and 15 yellow perch per tank.No mortality or HDPE accumulation in the fish was found in any treatments.Weight gain and condition factor of fish were not significantly impacted by HDPE(P>0.05).Compared to the control group,fish fed the 8%HDPE diet had significantly decreased levels of protein and ash(P<0.05).In response to the increasing levels of HDPE exposure,the hepatosomatic index value,hepatocyte size,and liver glycogen level were increased,but lipid content was reduced in the liver tissues.Compared to the control treatment,fish fed the 8%HDPE diet had significant accumulations of total bile acids and different metabolism pathways such as bile acid biosynthesis,pyruvate metabolism,and carnitine synthesis.Significant enterocyte necrosis was documented in the foregut of fish fed the 2%or 8%HDPE diet;and significant cell sloughing was observed in the midgut and hindgut of fish fed the 8%HDPE diet.Fish fed the 2%HDPE diet harbored different microbiota communities compared to the control fish.This study demonstrates that HDPE ranging from 100 to 125 mm in feed can be evacuated by yellow perch with no impact on growth.However,dietary exposure to HDPE decreased whole fish nutrition quality,altered nutrient metabolism and the intestinal histopathology as well as microbiota community of yellow perch.The results indicate that extended exposure may pose a risk to fish health and jeopardize the nutrition quality of aquacultured end product.This hypothesis remains to be investigated further.

Ploidy-, gender-, and dose-dependent alteration of selected biomarkers in Clarias gariepinus treated with benzo[a]pyrene

Naturally-occurring and artificially-induced polyploids have been documented in various fish species but to date no comparison has been reported of the impacts of ploidy on fish biomarker responses to organic pollutants.This study describes effects of ploidy,gender,and dose on biliary fluorescent aromatic compound（FAC） concentrations,hepatic ethoxyresorufin-O-deethylase（EROD） and glutathione S-transferase（GST） activities in one of the most commonly cultured warm-water species,the African catfish Clarias gariepinus.Recently matured male and female diploid and triploid fish were intraperitoneally（i.p.）injected with 0,5 or 25 mg/kg benzo[a]pyrene（BaP） and liver and gallbladder were sampled48 hr later.No significant differences were found between ploidies in bile concentrations of7,8 dihydrodiolbenzo[a]pyrene（7,8D BaP）,1-hydroxybenzo[a]pyrene（1-OH BaP） or3-hydroxybenzo[a]pyrene（3-OH BaP）.However,concentrations of the biliary FACs did differ between males and females at different dose of injection with generally higher concentrations in females at the low dose of BaP and higher concentrations in males at the higher BaP concentration.Hepatic EROD activity did not exhibit gender-dependent difference,whereas it was significantly higher in triploids than diploids.GST activities were not significantly influenced by any of the tested factors.This work advanced our understanding of the role of ploidy,gender,and dose in biotransformation of pollutants in fish.