Real-time determination of water status upon simultaneous zebrafish exposure to sublethal concentrations of CuSO4

Combined transcriptomics and metabolomics to reveal the effects of copper exposure on the liver of rainbow trout(Oncorhynchus mykiss)

Copper (Cu) is recognized as an essential trace elements for the body; However, excessive levels of Cu can lead to toxic effects. We investigated the effects of Cu2+(75 μg/L, 150 μg/L, and 300 μg/L) on the rainbow trout liver. Combination of transcriptome and metabolome analyses, the regulatory mechanisms of the liver under Cu stress were elucidated. The results showed that Cu affected the antioxidant levels, leading to disruptions in the normal tissue structure of the liver. Combined transcriptome and metabolome analyses revealed significant enrichment of the insulin signaling pathway and the adipocytokine signaling pathway. Additionally, Cu2+ stress altered the amino acid metabolism in rainbow trout by reducing serine and arginine levels while increasing proline content. Apoptosis is inhibited and autophagy and lipid metabolism are suppressed; In summary, Cu2+ stress affects energy and lipid metabolism, and the reduction of serine and arginine represents a decrease in the antioxidant capacity, whereas the increase in proline and the promotion of apoptosis potentially serving as crucial strategies for Cu2+ resistance in rainbow trout. These findings provided insights into the regulatory mechanisms of rainbow trout under Cu2+ stress and informed the prevention of heavy metal pollution and the selection of biomarkers under Cu pollution.

Use of acoustic stimulus to determine behavioral changes in zebrafish after Cd exposure in a water quality warning system

Behavioral changes in zebrafish are an effective early warning system to determine water quality. However, only a few studies have examined the response of zebrafish to non-chemical stimulus after exposure to a contaminant. Therefore, this study investigated the differences in the behavioral responses of zebrafish to acoustic stimuli before and after exposure to cadmium (Cd). Acoustic escape response sensitivity curves were obtained and analyzed, followed by the determination of sensitive stimulus conditions at 100 Hz and 97 dB with a duration of 30 s and an interval of 30 min. Zebrafish exhibit a significant acoustic escape response, which is significantly reduced after exposure to Cd. The results showed that zebrafish stop demonstrating acoustic escape responses when exposed to higher Cd concentrations or longer acoustic exposures. Based on these results, a novel method for detecting abnormal behavior in zebrafish by acoustic stimulation has been proposed, which is expected to reduce the false alarm rate of this type of water quality technology.

Assessing the disparity: comparative toxicity of Copper in zebrafish larvae exposes alarming consequences of permissible concentrations in Brazil

Copper (Cu) is a naturally occurring metal with essential micronutrient properties. However, this metal might also pose increased adverse environmental and health risks due to industrial and agricultural activities. In Brazil, the maximum allowable concentration of Cu in drinking water is 2 mg/L. Despite this standard, the impact of such concentrations on aquatic organisms remains unexplored. This study aimed to evaluate the toxicity of CuSO4 using larval zebrafish at environmentally relevant concentrations. Zebrafish (Danio rerio) larvae at 72 hr post-fertilization (hpf) were exposed to nominal CuSO4 concentrations ranging from 0.16 to 48 mg/L to determine the median lethal concentration (LC50), established at 8.4 mg/L. Subsequently, non-lethal concentrations of 0.16, 0.32, or 1.6 mg/L were selected for assessing CuSO4 -induced toxicity. Morphological parameters, including body length, yolk sac area, and swim bladder area, were adversely affected by CuSO4 exposure, particularly at 1.6 mg/L (3.31 mm ±0.1, 0.192 mm2 ±0.01, and 0.01 mm2 ±0.05, respectively). In contrast, the control group exhibited values of 3.62 mm ±0.09, 0.136 mm2 ±0.013, and 0.3 mm2 ±0.06, respectively. Behavioral assays demonstrated impairments in escape response and swimming capacity, accompanied by increased levels of reactive oxygen species (ROS) and lipid peroxidation. In addition, decreased levels of non-protein thiols and reduced cellular viability were noted. Data demonstrated that exposure to CuSO4 at similar concentrations as those permitted in Brazil for Cu adversely altered morphological, biochemical, and behavioral endpoints in zebrafish larvae. This study suggests that the permissible Cu concentrations in Brazil need to be reevaluated, given the potential enhanced adverse health risks of exposure to environmental metal contamination.