Histopathological effects of acute exposure to nickel oxide nanoparticles in the aquatic gastropod Physa acuta

The advances made in nanoscience and nanotechnology in the last decades have increased the presence in the environment of engineered nanoparticles, which are considered an emerging contaminant. Nanoparticles unique physical and chemical characteristics make them a product capable of affecting a myriad of organisms. They may also constitute a risk for human health by entering the trophic chain. In fact, the nanoparticles impact on the environment, aquatic organisms and human health are yet little known and further studies with innovative tools are necessary for the evaluation of the effects of toxicity. Nickel oxide nanoparticles have attracted increasing attention due to the potential use in a variety of applications. Developments in science and technology are increasing the quantity of products with nickel oxide nanoparticles and this trend will probably continue. Therefore, the environmental contamination with nickel oxide nanoparticles and consequent effects in the aquatic ecosystems are undeniable. Physa acuta is an invasive freshwater gastropod that has now a cosmopolitan distribution. It is a small deposit feeder and R-selected hermaphroditic species with rapid maturation and high reproductive rate. These characteristics allied with its ease of culture make it an excellent biological research model. The aim of this study was to assess the effects of the acute exposure to oxide nickel nanoparticles in the aquatic gastropod Physa acuta using histology as biomarker. With this purpose, two sequential acute bioassays with nickel oxide engineered nanoparticles with the snail Physa acuta were performed. The concentrations of contaminant tested were 2.7, 4.7, 8.2, 14.4, 25.2 mg/L and 21.3, 37.3, 65.3, 114.3, 200.0 mg/L. The samples subjected to concentrations corresponding to NOEC and LOEC were histologically processed using standard techniques. The histopathologies found were scored with a semi-quantitative method based on the extension of the lesions. The average of the extension of histological responses observed were calculated for each organ and tissue. In this study it was stated that the histology of several Physa acuta organs were affected by nickel oxide engineered nanoparticles, even in sub-lethal concentrations. All histopathological effects were observed in NOEC and LOEC. However, the extension of the lesions was dose dependent in most of the cases, this is in the generalized inflammatory response detected in snail tissues, the lesions observed in the foot and in the ganglia nervous tissue. The extension of histopathological changes observed in the hermaphrodite gland were significantly different from the control only at high levels of FCUP Histopathological effects of acute exposition to nickel oxide nanoparticles in the aquatic gastropod Physa acuta 6 NiO ENPs, this is at LOEC. In opposition, the extension of histopathological lesions observed in the glands from the foregut located near radula are not significantly different in NOEC and LOEC and even in the highest concentration the glands were not extensively affected. Histology demonstrated to be a promising tool as a biomarker of toxicity for studies with engineered nanoparticles in the aquatic environment, as well as the use of the aquatic gastropod Physa acuta. It is expected that these results will contribute to the understanding of the toxic effects of engineered nanoparticles in the aquatic environment and help to establish protocols for control and protection of the aquatic organisms.