Relationship closeness of tolerance to two neonicotinoids with their internal body burden in two estuarine resident marine crustaceans

The estuarine resident crustacean sand shrimp, Crangon uritai, has a higher tolerance to neonicotinoid insecticides than that of the kuruma prawns, Penaeus japonicus. However, the reason for the differential sensitivities between the two marine crustaceans remains to be understood. This study explored the mechanism underlying differential sensitivities based on insecticide body residues after exposing both said crustaceans to two insecticides (acetamiprid and clothianidin) with or without oxygenase inhibitor piperonyl butoxide (PBO) for 96 h. Two graded-concentration groups were formed; group H (1/15-1 times the 96-h LC₅₀ values) and L (one-tenth the concentration of group H). Results showed that the internal concentration in survived specimens tended to be lower in sand shrimp than in kuruma prawns. Co-treatment of PBO with two neonicotinoids not only increased sand shrimp mortality in the H group, but also altered metabolism of acetamiprid into its metabolite, N-desmethyl acetamiprid. Furthermore, molting during the exposure period enhanced bioconcentration of insecticides, but not affects survival. Collectively, the higher tolerance of sand shrimp than that of kuruma prawns to the two neonicotinoids can be explained by lower bioconcentration potential and more involvement of oxygenase in their alleviating lethal toxicity.

In silico prediction of acute chemical toxicity of biocides in marine crustaceans using machine learning

Biocides are a heterogeneous group of chemical substances intended to control the growth or kill undesired organisms. Due to their extensive use, they enter marine ecosystems via non-point sources and may pose a threat to ecologically important non-target organisms. Consequently, industries and regulatory agencies have recognized the ecotoxicological hazard potential of biocides. However, the prediction of biocide chemical toxicity on marine crustaceans has not been previously evaluated. This study aims to provide in silico models capable of classifying structurally diverse biocidal chemicals into different toxicity categories and predict acute chemical toxicity (LC₅₀) in marine crustaceans using a set of calculated 2D molecular descriptors. The models were built following the guidelines recommended by the OECD (Organization for Economic Cooperation and Development) and validated through stringent processes (internal and external validation). Six machine learning (ML) models were built and compared (linear regression: LR; support vector machine: SVM; random forest: RF; feed-forward backpropagation-based artificial neural network: ANN; decision trees: DT and naïve Bayes: NB) for regression and classification analysis to predict toxicities. All the models displayed encouraging results with high generalisability: the feed-forward-based backpropagation method showed the best results with determination coefficient R² values of 0.82 and 0.94, respectively, for training set (TS) and validation set (VS). For classification-based modelling, the DT model performed the best with an accuracy (ACC) of 100 % and an area under curve (AUC) value of 1 for both TS and VS. These models showed the potential to replace animal testing for the chemical hazard assessment of untested biocides if they fall within the applicability domain of the proposed models. In general, the models are highly interpretable and robust, with good predictive performance. The models also displayed a trend indicating that toxicity is largely influenced by factors such as lipophilicity, branching, non-polar bonding and saturation of molecules.

Effects of commercial formulations of glyphosate on marine crustaceans and implications for risk assessment under temperature changes

Glyphosate-based formulations are the most commonly used herbicides worldwide with the risk of potential contamination of aquatic bodies. The present study assessed the response of four marine crustaceans to three different brands of herbicides Roundup®Platinum, Efesto® and Taifun® MK CL.T, under two selected temperatures of 20 °C and 30 °C. The harpacticoid copepod Tigriopus fulvus, the anostracan Artemia franciscana, the amphipod Corophium insidiosum and the isopod Sphaeroma serratum were chosen as testing organisms. Effects of herbicides and temperatures were assessed by estimating lethal concentrations. The results showed that the high temperature rises the toxicity of glyphosate with an increase of mortality of all the tested species. This is an important aspect for future risk assessments of pesticides under global climate change scenarios. Efesto® resulted the most toxic brand, showing C. insidiosum the most sensitive with 96 h-LC50 values of 3.25 mg/L acid equivalent (a.e.) at 30 °C and 7.94 mg/L a.e. at 20 °C followed by T. fulvus while A. franciscana and S. serratum were the less sensitive. This study provides important information for assessing the toxic effects of three different brands of glyphosate-based herbicides on non-target marine organisms suggesting that they should be carefully managed to minimize any negative impact on marine organisms.