Neonicotinoid pesticides are one of the most commercialized groups worldwide. Their application in agriculture aims to control pests through a systemic mode of action which is not specific to target species. Our study aimed to evaluate the effects of the insecticide Actara^® [active ingredient thiamethoxam (TMX)] on a non-target species, Girardia tigrina. Therefore, acute and sublethal endpoints, such as mortality, feeding activity, locomotion and behavioral biomarkers were assessed. Actara^® exerted low toxicity towards the planarian Girardia tigrina, showing a 96 h LC₅₀ value of 77.6 mg TMX·L⁻¹ (95% C.I: 74.1–81.2 mg TMX·L⁻¹; R² = 0.85). At the sublethal level, Actara^® exerted no effect on regeneration of photoreceptors and auricles of planarians after 24 and 48 h post-exposure (NOEC > 7.8 mg TMX·L⁻¹). The feeding rate of planarians was significantly increased by Actara^®, but only at the highest tested concentration (LOEC = 7.8 mg TMX·L⁻¹). Planarians showed to be less sensitive to the active ingredient TMX compared to other freshwater species. This might be explained by the presence of a high proportion of sub-types of acetylcholine receptors in planarians, exhibiting low binding affinity sites for TMX, an acetylcholine partial agonist. The comparison between effects induced by Actara^® with the ones caused by other formulations, in planarians, might support our understanding of how other unknown ingredients can modify the uptake, and bioavailability of such substances, as well as the detoxification capacity of planarians, all of which influences toxicity.

Understanding the interplay among organophosphorus flame retardants (OPFRs), microplastics, and freshwater organisms is crucial for unravelling the dynamics within freshwater environments and foreseeing the potential impacts of organic pollutants and plastic contamination. For that purpose, the present research assessed the exposure impact of 10 mg L⁻¹ flame-retardant aluminium diethylphosphinate (ALPI), 10 μg mg⁻¹_liver microplastics polyurethane (PU), and the combination of ALPI and PU on the freshwater planarian Girardia tigrina. The exposure to both ALPI and PU revealed a sequential effect, i.e., a decrease in locomotor activity, while oxidative stress biomarkers (total glutathione, catalase, glutathione S-transferase, lipid peroxidation) and metabolic responses (cholinesterase activity, electron transport system, and lactate dehydrogenase) remained unaffected. Despite this fact, it was possible to observe that the range of physiological responses in exposed organisms varied, in particular in the cases of the electron transport system, cholinesterase activity, glutathione S-transferase, catalase, and levels of total glutathione and proteins, showing that the energetic costs for detoxification and antioxidant capacity might be causing a lesser amount of energy allocated for the planarian activity. By examining the physiological, behavioural, and ecological responses of planarians to these pollutants, insights can be gained into broader ecosystem-level effects and inform strategies for mitigating environmental risks associated with OPFRs and microplastic pollution in freshwater environments.

Thiamethoxam (TMX) is a systemic neonicotinoid that acts as a partial agonist of the nicotinic acetylcholine receptors (nAChRs). However, target species have shown resistance to formulations based on such neonicotinoids, which can also be expected for non-target insects. This research aimed to study the effects of a formulation based on TMX [Cruiser® 350 FS (CRZ)] on the life traits of Chironomus xanthus filial generation (F1) and compare it with the parental generation (P). Environmentally relevant concentrations of CRZ significantly decreased larvae growth P generation , also slowing and decreasing their emergence. Larvae of the F1 generation were less sensitive than their parents, suggesting that the progeny were able to thrive and perform basic physiological functions better than the parental generation. Our results highlight that insect resistance to neonicotinoids may be associated with the better performance of the filial generation, which is related to the change in affinities of the active ingredient for the sub-units constituting the nAChRs subtypes of F1 organisms, inherited from P organisms that were able to survive and reproduce. Moreover, further studies using biochemical and omics tools should be performed to disentangle the specific changes occurring at the nAChRs throughout insect development.

Background: The active secondary metabolites of various Kalanchoe species are promising for controlling insects and other agricultural pests. Objective: This study aimed to evaluate the mortality and immune responses of the leafcutter ant Atta sexdens (L.) after treatment with Kalanchoe ×laetivirens (Desc.) aqueous extract. The effects on an aquatic organism used as a bioindicator, Chironomus xanthus (Rempel), were also evaluated. Methods: Different K. ×laetivirens concentrations were prepared by dilution in honey to assess the toxicity and determine the median lethal concentration (LC50) for A. sexdens workers. The haemocytes of workers treated with a sublethal concentration (0.005 g/mL) were counted. Results: The plant extracts induced high mortality in A. sexdens workers. All concentrations, except 0.001 g/mL, increased mortality rates. The sublethal concentration negatively affected the immune system of A. sexdens workers 48 and 72 h after ingestion. The flavonoids 4″″-acetylsagittatin A, sagittatin A and the nucleosides uridine and adenosine were identified. The LC50 of the K. ×laetivirens (128.1 mg /L) was determined for the non-target organism, C. xanthus. Conclusion: These natural compounds can be used in future research to plan alternative control strategies for leafcutter ants in forests and other agroecosystems.