Mechanisms of toxic action of copper and copper nanoparticles in two Amazon fish species: Dwarf cichlid (Apistogramma agassizii) and cardinal tetra (Paracheirodon axelrodi)

Abstract

Copper oxide nanoparticles (nCuO) are widely used in boat antifouling paints and are released into the environment, potentially inducing toxicity to aquatic organisms. The present study aimed to understand the effects of nCuO and dissolved copper (Cu) on two ornamental Amazon fish species: dwarf cichlid (Apistogramma agassizii) and cardinal tetra (Paracheirodon axelrodi). Fish were exposed to 50% of the LC for nCuO (dwarf cichlid 58.31μgL and cardinal tetra 69.6μgL) and Cu (dwarf cichlid 20μgL and cardinal tetra 22.9μgL) for 24, 48, 72 and 96h. Following exposure, aerobic metabolic rate (ṀO), gill osmoregulatory physiology and mitochondrial function, oxidative stress markers, and morphological damage were evaluated. Our results revealed species specificity in metabolic stress responses. An increase of ṀO was noted in cardinal tetra exposed to Cu, but not nCuO, whereas ṀO in dwarf cichlid showed little change with either treatment. In contrast, mitochondria from dwarf cichlid exhibited increased proton leak and a resulting decrease in respiratory control ratios in response to nCuO and Cu exposure. This uncoupling was directly related to an increase in reactive oxygen species (ROS) levels. Our findings reveal different metabolic responses between these two species in response to nCuO and Cu, which are probably caused by the differences between species natural histories, indicating that different mechanisms of toxic action of the contaminants are associated to differential osmoregulatory strategies among species.

Measurement of mitochondrial respiration in permeabilized fish gills

“…The addition of cytochrome c led to only a small percentage increase in respiration rate (Table 1), confirming that the preparations were of high quality. In comparison to semi-isolated, Dounce-homogenized, gill tissues (Braz-Mota et al, 2018), our preparation shows greater RCR values (7.4 versus 2.6-5.5), further confirming the high quality of mitochondrial preparations using this technique (Table 1). It is interesting to note that our respiration values are lower than those reported by Braz-Mota et al 2018, although this is expected and has been shown in studies comparing different mitochondrial preparations in other taxa (Saks et al, 1998;Picard et al, 2011;Mahalingam et al, 2017).…”

Review of Copper and Copper Nanoparticle Toxicity in Fish

“…CuNPs were less toxic than dissolved copper for the two studied fish species, namely dwarf cichlid (Apistogramma agassizii) and cardinal tetra (Paracheirodon axelrodi). Fishes were exposed to 50% of the LC50 for CuO-NPs (dwarf cichlid, 58.31 μg/L; cardinal tetra, 69.6 μg/L) and Cu (dwarf cichlid, 20 μg/L; cardinal tetra, 22.9 μg/L) for 24, 48, 72, and 96 h. Oxidative stress was promoted in the dwarf cichlid [ 166 ]. CuNPs were also shown to be toxic to tilapia, a freshwater edible fish, in comparison to dibutyltin at an exposure concentration of 15 mg/L, inducing oxidative stress and hindering fish growth and development [ 167 ].…”

Interaction of Copper-Based Nanoparticles to Soil, Terrestrial, and Aquatic Systems: Critical Review of the State of the Science and Future Perspectives

“…There is currently a significant gap in our knowledge about CuO-NPs toxicity to aquatic animals. In general, the Cu(O) NPs toxicity may be a potential environmental concern for crustaceans, as LC50 values are within an order of magnitude of predicted wastewater concentrations, while chronic and developmental toxicity are a more relevant concern for fishes (Braz-Mota et al 2018). A few studies have noted bioactivity in these animals at high concentrations (20 μg L -1 ).…”

“…Copper (Cu) is a naturally occurring ubiquitous element present in the environment with a concentration around 60 g per ton in the Earth's crust (Ojha et al 2017) and essential micronutrient for plant growth at certain concentrations and is known to play important roles in mitochondrial respiration, hormone signalling, cell wall metabolism, iron mobilization, and electron transport (Yruela 2009). However, at higher concentrations, Cu is generally toxic to plants and other organisms including algae, mussels, crustaceans, and fish (Aruoja et al 2009;Braz-Mota et al 2018;Katsumiti et al 2018;Ruiz et al 2015). While there is no data available on the concentration of CuO-NPs in the soil total Cu could range from 2-100 mg kg -1 in unpolluted soils (Nagajyoti et al 2010).…”