Metabolic pathways of methylmercury in rotifer Brachionus plicatilis

AQUA Tox: A web tool for predicting aquatic toxicity in rotifer species using intrinsic explainable models

The widespread use of chemicals in various industries, including agriculture, cosmetics, pharmaceuticals, and textiles, poses significant environmental risks, particularly in aquatic ecosystems. This study focuses on the toxicity of organic compounds on two rotifer species, Brachionus calyciflorus and Brachionus plicatilis, widely used as bioindicators in ecotoxicology. A database of toxicity data (LC50) was compiled and QSAR/QSTR models were developed to predict chemical toxicity in both freshwater (FW) and saltwater (SW) environments. Using molecular descriptors, the study identified critical factors influencing toxicity, such as hydrophobicity and the presence of chlorine atoms. The models demonstrated strong predictive performance, with R² values exceeding 70 % for both FW and SW conditions. Key descriptors influencing toxicity included hydrophobicity and chlorine content. The models demonstrated strong predictive performance, with R² values exceeding 70 %. A user-friendly web application was developed, enabling the scientific community to assess the aquatic toxicity of chemicals. This tool aids in the design of safer, more sustainable substances, facilitating regulatory compliance and minimizing environmental impacts. The findings highlight the importance of combining computational methods with technological applications for environmental protection.

Toxicity of methylmercury in aquatic organisms and interaction with environmental factors and coexisting pollutants: A review

Mercury is a hazardous heavy metal that is distributed worldwide in aquatic ecosystems. Methylmercury (MeHg) poses significant toxicity risks to aquatic organisms, primarily through bioaccumulation and biomagnification, due to its strong affinity for protein thiol groups, which results in negative effects even at low concentrations. MeHg exposure can cause various physiological changes, oxidative stress, neurotoxicity, metabolic disorders, genetic damage, and immunotoxicity. To assess the risks of MeHg contamination in actual aquatic ecosystems, it is important to understand how MeHg interacts with environmental factors such as temperature, pH, dissolved organic matter, salinity, and other pollutants such as microplastics and organic compounds. Complex environmental conditions can cause potential toxicity, such as synergistic, antagonistic, and unchanged effects, of MeHg in aquatic organisms. This review focuses on demonstrating the toxic effects of single MeHg exposure and the interactive relationships between MeHg and surrounding environmental factors or pollutants on aquatic organisms. Our review also recommends further research on biological and molecular responses in aquatic organisms to better understand the potential toxicity of combinational exposure.

Changes in transcriptome regulations of a marine rotifer Brachionus plicatilis under methylmercury stress

Mercury (Hg), a heavy metal pollutant worldwide, can be transformed into methylmercury (MeHg) by various aquatic microorganisms in water, thus accumulating along the aquatic food chain and posing a particular challenge to human health. Zooplankton plays a crucial role in aquatic ecosystems and serves as a major component of the food chain. To evaluate the effects of MeHg on the rotifer Brachionus plicatilis and reveal the underlying mechanism of these effects, we exposed B. plicatilis to MeHg by either direct immersion or by feeding with MeHg-poisoned Chlorella pyrenoidesa, respectively, and conducted a transcriptomic analysis. The results showed that B. plicatilis directly exposed to MeHg by immersion showed significant enrichment of the glutathione metabolism pathway for detoxification of MeHg. In addition, the exposure to MeHg by feeding induced a significant enrichment of lysosome and notch signaling pathways of rotifers, supporting the hypothesis that MeHg can induce autophagy dysfunction in cells and disturb the nervous system of rotifers. In two different routes of MeHg exposure, the pathway of cytochrome P450 in rotifers showed significant enrichment for resisting MeHg toxicity. Our results suggest further studies on the potential mechanism and biological responses of MeHg toxicity in other links of the aquatic food chain.