Growth Retardation in Silver Carp (Hypophthalmichthys molitrix) in the Middle Reaches of the Yangtze River and its Possible Causal Agents

Abstract

Organophosphate esters (OPEs) are a class of emerging contaminants and are found to be ubiquitous in various environmental matrices owing to their wide applications. Furthermore, OPEs were reported to have the capacity to induce growth retardation in fish in laboratory exposure experiments. However, their impacts on wild fish remain largely unknown. In this study, 11 out of 19 OPEs were detected in silver carp from the middle reaches of the Yangtze River, with concentrations ranging from 7.72 to 257.72 μg/kg dry weight. Moreover, the concentrations of Σ11OPEs were negatively associated with the body weight, standard length, and total length of silver carp. Growth retardation, including weight loss and body length decrease, was also observed in silver carp exposed to OPEs at their environmentally relevant concentrations in a laboratory-controlled experiment. Furthermore, exposure to OPEs did not affect the concentration of the growth hormone, but significant changes in the content of thyroxine and expression of genes included in the hypothalamic–pituitary–thyroid axis were observed, indicating that thyroid hormone-disrupting effects contributed to the growth retardation in silver carp. Our findings provide a novel insight into the threat of OPEs to fishery resources, calling for more regulation of OPEs in the aquatic environment.

Lipid Metabolic Disorders Induced by Organophosphate Esters in Silver Carp from the Middle Reaches of the Yangtze River

“…The exposure concentrations were selected according to their known environmental concentration levels and 10 times the environmental concentrations of the 11 OPEs determined in water samples from the middle reaches of the Yangtze River. 20 Our previous study reported that exposure to each of the two concentrations of OPEs significantly decreased the body weight and body length of silver carp. 20 In this study, a significant increase in CHO level was observed in the 66.28 ng/L OPE exposure group.…”

“…Silver carp were obtained from the Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, and the mean weight of the fish was 0.199 ± 0.040 g, according to our previous study . The mean values of total length and standard length were 2.85 ± 0.197 and 2.24 ± 0.156 cm, respectively, as described previously . Both this study and our previous study were based on the same fish exposure experiment, but the objectives of the two studies were completely different.…”

“…20 The mean values of total length and standard length were 2.85 ± 0.197 and 2.24 ± 0.156 cm, respectively, as described previously. 20 Both this study and our previous study were based on the same fish exposure experiment, but the objectives of the two studies were completely different. In the previous study, the developmental toxicity of OPEs in silver carp was evaluated, 20 whereas in this study, the lipid metabolic disorder was studied.…”

“…The measured concentrations of OPEs in exposure solutions were comparable with the corresponding nominal concentrations as reported in our previous study. 20 Silver carp were fed twice a day with a commercial feed. After exposure, the serum and liver were collected for further analysis.…”

“…These results suggest that OPEs may have potential toxicities for exposed wild fish. Laboratory research has demonstrated that OPEs induce a variety of adverse effects in fish, such as growth inhibition, hepatotoxicity, neurotoxicity, metabolic disruption toxicity, and endocrine disrupting effects. − However, the ecotoxicological effects of OPEs on wild fish remain largely unknown. Limited studies have reported that some OPEs cause mass mortality of crucian carp embryos in Taihu Lake and growth inhibition of silver carp in the Yangtze River, suggesting that the contamination of OPEs in natural aquatic ecosystems might cause fish population/biomass decline. , …”