Evaluation of the pesticide Oberon on a model organism Drosophila melanogaster via topical toxicity test on biochemical and reproductive parameters

Sublethal and lethal effects of avermectin on reproductive success, hormonal regulation, and population dynamics of the oriental fruit fly, Bactrocera dorsalis

BACKGROUND

The oriental fruit fly, Bactrocera dorsalis, causes significant economic losses in fruit production because of its high reproductive rate and adaptability. The current study investigated the sublethal and lethal effects of avermectin, a macrocyclic lactone insecticide, on the F0 and F1 generations of B. dorsalis.

RESULTS

This study demonstrated that exposure to avermectin with sublethal and lethal (LC5, LC20, and LC50) concentrations reduced mating rates, prolonged pre-mating periods, and lowered levels of juvenile hormone (JH) and 20-hydroxyecdysone (20E). Furthermore, avermectin exposure resulted in a decrease in vitellogenin (Vg) and vitellogenin receptor (VgR) levels, with downregulated expression of the corresponding genes. Subsequent investigations revealed that avermectin exposure led to reduced sugar accumulation indicated by decreased glycogen, glucose and trehalose levels, alongside impaired trehalase activities and lower triglyceride content in the F0 generation of B. dorsalis. These metabolic disruptions contributed to decreased hatching, pupation and emergence rates, and lower pupal weights and reproductive parameters (as demonstrated by life table parameters) in the F1 generation. Furthermore, increased activities of detoxifying enzymes such as glutathione S-transferase, carboxylesterase and cytochrome P450 monooxygenases were found, suggesting an adaptive response to detoxify avermectin.

CONCLUTION

These findings highlight the potential long-term impacts of avermectin on B. dorsalis population dynamics and underscore the need for incorporating considerations of sublethal effects into integrated pest management strategies. © 2025 Society of Chemical Industry.

Lipid Metabolism as a Target Site in Pest Control

Lipid metabolism is essential to insect life as insects use lipids for their development, reproduction, flight, diapause, and a wide range of other functions. The central organ for insect lipid metabolism is the fat body, which is analogous to mammalian adipose tissue and liver, albeit less structured. Various other systems including the midgut, brain, and neural organs also contribute functionally to insect lipid metabolism. Lipid metabolism is under the control of core lipogenic [e.g. acetyl-CoA-carboxylase (ACC), fatty acid synthase (FAS), perilipin 2 (LSD2)], and lipolytic (lipases, perilipin 1) enzymes that are primarily expressed in the fat body, as well as hormones [insulin-like peptides (ILP), adipokinetic hormone (AKH)], transcription factors (SREBPs, foxO, and CREB), secondary messengers (calcium) and post-translational modifications (phosphorylation). Essential roles of the fat body, together with the fact that proper coordination of lipid metabolism is critical for insects, render lipid metabolism an attractive target site in pest control. In the current chapter, we focus on pest control tactics that target insect lipid metabolism. Various classes of traditional chemical insecticides [e.g. organophosphates, pyrethroids, neonicotinoids, and chitin synthesis inhibitors (Sects. 2.1 and 2.2)] have been shown to interfere with lipid metabolism, albeit it is not their primary site of action. However, the discovery of "lipid biosynthesis inhibitors", tetronic and tetramic acid derivatives commonly known as ketoenols (Sect. 2.3), was a milestone in applied entomology as they directly target lipid biosynthesis, particularly in sucking pests. Spirodiclofen, spiromesifen, and spirotetramat targeting ACC act against various insect and mite pests, while spiropidion and spidoxamat have been introduced to the market only recently. Efforts have concentrated on the development of chemical alternatives, such as hormone agonists and antagonists (Sect. 2.4), dsRNA-based pesticides that depend on RNA interference, which have great potential in pest control (Sect. 2.5) and other eco-friendly alternatives (Sect. 2.6).

Repurposing Insecticides for Mosquito Control: Evaluating Spiromesifen, a Lipid Synthesis Inhibitor against Aedes aegypti (L.)

The growing resistance of Aedes aegypti (L.) to conventional insecticides presents a major challenge in arbovirus control, necessitating the exploration of alternative insecticidal chemistries. Spiromesifen, derived from spirocyclic tetronic acids, is widely used against agricultural pests and is crucial in resistance management due to its unique lipid synthesis inhibition. This study evaluates the insecticidal activity of spiromesifen against temephos-resistant Ae. aegypti populations, focusing on larval body weight, volume, biochemical composition, and adult female reproductive potential. Spiromesifen demonstrated effective larvicidal activity, significantly reducing adult emergence. Resistance to spiromesifen was not observed, with resistance ratios (RR50, RR90) ranging from 0.36- to 3.31-fold. Larvae exposed to LC50 showed significant reductions in body weight and volume, and reduced carbohydrate, lipid, and protein contents. Enhanced catalase activity and malondialdehyde levels indicated increased oxidative stress and lipid peroxidation, highlighting its effects on lipid metabolism. Spiromesifen also exhibited sterilizing effects, significantly reducing fecundity and fertility in adult females, thereby impacting Ae. aegypti reproductive capacity. These findings highlight the potential of spiromesifen as a component of integrated vector management strategies, especially in regions with prevalent insecticide resistance in Ae. aegypti, serving as an effective larvicide and impacting adult reproductive outcomes.

Insecticidal activity of the organotellurium 2-Phenylethynyl-Butyltellurium on the Drosophila melanogaster model

2-Phenylethynyl-Butyltellurium (PEBT) is a synthetic organotellurium compound that has shown various pharmacological properties on mammals without any signs of toxicity, but its effects on insects have not been reported before. Therefore, the aim of this study was to assess whether acute exposure to PEBT would promote an insecticidal effect against Drosophila melanogaster. The flies were exposed to three concentrations of PEBT (0.325 µmol L-1, 1.300 µmol L-1, and 5.200 µmol L-1) and a control solution (vehicle), using 450 flies per treatment (three repetitions of 150 flies), for 48 hours. Negative geotaxis and open field tests were performed (in vivo) after 24 and 48h, and acetylcholinesterase (AChE) activity was assessed (ex vivo) after 48h. Also, the mortality rate, 50% Lethal Concentration (LC50), 80% Lethal Concentration (LC80), and 95% Lethal Concentration (LC95) were calculated. Our results show that PEBT presented insecticidal activity against Drosophila melanogaster at all tested concentrations, which caused locomotor impairment and increased acetylcholinesterase activity in the flies' heads.

Spiromesifen contributes vascular developmental toxicity via disrupting endothelial cell proliferation and migration in zebrafish embryos

Spiromesifen (SPF) is a specific contact pesticide, which has been widely used to control the growth of sucking insects like mites and whiteflies on crops. Although its residues in crops and effects on organisms has been extensively reported, its impact on the vasculature is still not being reported. In the present study, using human umbilical vein endothelial cells (HUVECs) and zebrafish embryos, we investigated the effects of SPF on blood vessel development and its mechanism of action. SPF exposure triggered abnormal blood vessel development, including vascular deletions and malformations, inhibition of CCV remodeling, and decrease of SIV areas. SPF exposure also obstructed the migration of endothelial cell from caudal hematopoietic tissue in zebrafish embryos. SPF damaged cytoskeleton, caused cell cycle arrest, inhibited the viability and migration of HUVECs. In addition, SPF also inhibited the expression of the VEGF/VEGFR pathway-related genes (hif1a, vegfa, flt1, and kdrl), cell cycle-related genes (ccnd1, ccne1, cdk2, and pcna), and Rho/ROCK pathway-related genes (itgb1, rho, rock, mlc-1, and vim-1). Taken together, SPF may inhibit the proliferation and migration of vascular endothelial cells through disturbing cytoskeleton via the Rho/ ROCK pathway, resulting in vascular malformation. Our study contributes to potential insight into the mechanism of SPF toxicity in angiocardiopathy.

Spiromesifen conferred abnormal development in zebrafish embryos by inducing embryonic cytotoxicity via causing oxidative stress

Spiromesifen (SPF) is widely used in agriculture to protect against herbivorous mites, whose residues may be harmful to the environment. However, the toxicity assessment of SPF is insufficient. Here, we investigated the toxicological effects of SPF using zebrafish embryos as an animal model. The results showed that SPF exposure solutions at 10, 20, 30, and 40 μM caused cytotoxicity in zebrafish embryos such as reactive oxygen species (ROS) accumulation, mitochondrial membrane potential decrease, cell division arrest, and apoptosis, which further led to developmental toxicity in zebrafish embryos including delayed hatching, decreased survival rate and spontaneous curling rate, and severe morphological deformities. SPF also induced apoptosis via changes in the expressions of apoptosis-related marker genes, caused immunotoxicity by reducing the number of macrophages and the activity of AKP/ALP and increasing inflammatory factors, and disturbed endogenous antioxidant systems via changes SOD, CAT, and GST activities as well as MDA and GSH contents. Therefore, the potential mechanism that caused embryonic developmental toxicity appeared to be related to the generation of oxidative stress by an elevation in ROS and changes in apoptosis-, immune-, antioxidant-related markers. The antioxidant system and inflammatory response simultaneously participated in and resisted the threat of SPF to prevent tissue damage. Taken together, spiromesifen induced oxidative stress to contribute to developmental toxicity in zebrafish embryos by inducing embryonic cytotoxicity. Our study provides new insight into the toxicity assessment of SPF to non-target organisms.

Ecotoxicological effects of dietary titanium dioxide nanoparticles on metabolic and biochemical parameters of model organism Galleria mellonella (Lepidoptera: Pyralidae)

Nanoparticles (NPs) are now being used in many industrial activities, such as mining, paint and glass industries. The frequent industrial use of NPs contributes to environmental pollution and may cause cellular and oxidative damage in native organisms. In this study, the toxic effects of titanium dioxide nanoparticles (TiO₂ NPs) were investigated using Galleria mellonella larvae as a model insect species. Alterations in cell damage indicators, such as alanine transferase, aspartate transferase, lactate dehydrogenase, non-enzymatic antioxidants and biochemical parameters, were determined in the hemolymph of G. mellonella larvae exposed to TiO₂ NPs at different concentrations (5, 50, 250 and 1250 μg/mL) in their diets. TiO₂ NPs caused concentration-dependent cellular damage in the hemolymph of G. mellonella larvae and increased the levels of the non-enzymatic antioxidants uric acid and bilirubin. In addition, total protein in hemolymph significantly decreased at the highest concentration (1250 μg/mL) of TiO₂ NPs. Level of the urea increased at the highest concentration (1250 μg/mL) of TiO₂ NPs, whereas the amount of glucose was not affected. These findings demonstrated that TiO₂ NPs caused concentration-dependent toxic effects on G. mellonella larvae.

Contraceptive and biochemical effect of juice extract of Allium cepa, Allium sativum, and their combination in Canton S fruit flies

This study determines the contraceptive activity of Allium sativa (Garlic) and Allium cepa (Onion) juices on reproductive output and development of Drosophila melanogaster. The fruit flies were divided and grouped into 5, group A serves as the control, group B serves as the onion group, group C serves as the garlic group, group D serves as the onion + garlic group, while group E serves as the standard contraceptive group. Biochemical parameters measured were superoxide dismutase (SOD), Catalase (CAT), Glutathione-S-transferase (GST), malondialdehyde (MDA), nitric oxide (NO), total cholesterol (TC), triglyceride, mating test, and negative geotaxis. There was a significant reduction in the levels of MDA in onion, garlic, onion + garlic groups when compared with the control, in contrast, a significant increase was observed in SOD, CAT, and GST activities. Furthermore, there was a significant reduction in nitric oxide levels in garlic, onion + garlic extract with a corresponding increase in the standard contraceptive group. There was a significant reduction in the concentration of TC and HMG-CoA in garlic and standard contraceptive groups when compared with the control while triglyceride revealed a considerable increase in the garlic group when compared with the control. The mating test showed there was a considerable reduction in the onion, garlic, onion + garlic, and standard contraceptive when compared with the control. Taken together, Allium sativum proved to serve as a better contraceptive in D. melanogaster as a possible effective option for contraceptives, which is further, supported by their strong antioxidant activity. PRACTICAL APPLICATIONS: A. cepa and A. sativum are sources of dietary phytocompounds with proven antioxidant activities. The contraceptive activity of A. cepa and A. sativum juice extract was investigated. The results showed that A. cepa and A. sativum and their combination prove to serve as a better effective option for contraceptives in D. melanogaster. The observed results could provide the potential application of A. cepa and A. sativum as an alternative therapy for contraceptives.

Degradation mechanism of fipronil and its transformation products, matrix effects and toxicity during the solar/photo-Fenton process using ferric citrate complex

This study presents the degradation of fipronil in sewage treatment plant (STP) effluent by photo-Fenton at near neutral pH (pH 6.0) using Fe³⁺/Citrate complex. 83% of fipronil degradation was reached using a molar iron/citrate ratio of 1:3 (192 μmol L^-1 of Fe³⁺/576 μmol L^-1 of citrate). Photo-Fenton reduced the toxicity of treated solutions as according to the survival of Drosophila melanogaster exposed to non-treated and treated samples. Control experiments performed in distilled water using 32 μmol L^-1 of Fe³⁺/96 μmol L^-1 of citrate achieved 98% of fipronil degradation within 100 kJ m^-2 (UV-A radiation, k = 30 × 10^-3 kJ^-1 m² and t_1/2 = 23 kJ m^-2), thus indicating that fipronil degradation is impaired by natural organic matter and inorganic ions present in STP effluent. Degradation was faster under solar radiation, as the same efficiency (98%) was obtained after 75 kJ m^-2 (k = 63 × 10^-3 kJ^-1 m² and t_1/2 = 11 kJ m^-2). In addition, pathways of fipronil degradation using Fe³⁺/Citrate under solar and UV-A radiation were investigated and transformation products proposed. Results revealed that the HO^• attack occurred preferentially in the pyrazole ring. Eight transformation products were identified by UHPLC-Q-TOF-MS and four are unprecedented in the literature. Control experiments in distilled water demonstrated that toxicity reduction is related to fipronil degradation and that transformation products are less toxic than fipronil. Furthermore, toxicity of STP fortified with fipronil was reduced after photo-Fenton. These results demonstrate the feasibility of applying this process using Fe³⁺/Citrate complex for fipronil degradation in a real matrix.