Progress 07/15/23 to 07/14/24
Outputs
Target Audience:The target audience of our research are scientists working in the fields of agriculture, pesticide development, neurobiology, entomology, risk assessment, and conservation biology. The research findings are useful to people working in multiple sectors, including academia, government, private companies, and NGOs. The target audiences were reached through presentations at scientific conferences and university departments and will soon be reached through journal publications. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The PD has trained a half-time faculty assistant on the project. The faculty assistant will be an author on the Lepidoptera paper being submitted. Additionally, two undergraduate students gained research experience by working on parts of the project. At Iowa State University, the co-PD trained a graduate student in entomology on the project. This work will be part of the graduate student's masters thesis. The following presentations on this project were made in the last one year: Jurenka RA, Adeyanju O, Bradbury SP, Gorman CL, Krishnan N. 2023 Neonicotinoids and pyrethroids can cause arrested ecdysis in Coleoptera. Entomological Society of America, National Harbor, MD. Stewart J, Bradbury S, Jurenka R, Krishnan N. 2-24 Evaluating the effect of neonicotinoid insecticides on insect ecdysis movements. Eastern Branch Entomological Society of America, Morgantown, WV. How have the results been disseminated to communities of interest?The presentations made by the project personnel at symposiums in national conferences were attended by people working in state and federal agencies, pesticide manufacturing companies, and academia. What do you plan to do during the next reporting period to accomplish the goals?By the next and final reporting period, we plan to finish undertaking Objective c (the only remaining objective). Specifically, we will undertake more immunostaining of lepidopteran and coleopteran nerve cords so we can obtain definitive results. We will also finetune our hypothesis, including generating new adverse outcome pathways, based on obtained and new results. We will be submitting the Lepidoptera paper, which encompasses Objectives a and b, in the next two weeks. We will be submitting a Coleoptera paper (Objective d) by the end of this year. We will continue making presentations at different venues.
Impacts
What was accomplished under these goals?
Under Objective a, we topically tested additional compounds on corn earworms and fall armyworms (previously we had tested imidacloprid, nicotine, nitenpyram, sulfoxaflor, acetamiprid, thiacloprid, pilocarpine, and mecamylamine): chlorpyrifos (oxon organophosphate), naled (thionate organophosphate), beta-cyfluthrin (type II pyrethroid), cypermethrin (type II pyrethroid), and permethrin (type I pyrethroid). Results with nicotinic acetylcholine receptor (nAChR) agonists suggest that pupal ecdysis is likely mediated by the putative α1 and β1 subunits of nAChRs. The reason we undertook studies with organophosphates is because pilocarpine, a muscarinic acetylcholine receptor (mAChR) agonist, has very low solubility in acetone/DMF, which precluded testing of sufficiently high doses. Other mAChR agonists had similarly low solubility. Thus, to rule out mAChR involvement in arrested ecdysis (AE), we undertook studies with organophosphate compounds that act on both mAChR and nAChR. The organophosphates showed intermediate to low rates of AE, which supports the hypothesis that only nAChRs are involved in eliciting AE. Additionally, we tested pyrethroids because papers published in literature indicated that inhibitory neurotransmitters are also involved in pupal regulation, and GABA, one target of pyrethroid insecticides, is a major inhibitory neurotransmitter in insects. Studies have shown that type II pyrethroids can serve as antagonists of GABA receptors at lower doses than type I pyrethroids. Our findings supported this: type II pyrethroids elicited AE at higher doses than type I pyrethroids. This suggests that GABA is also involved in regulation of insect pupal ecdysis. Objective b work was undertaken previously (see 2023 annual report). Under Objective c, we have obtained a CCAP antibody that is able to identify the neurons of the central nervous system that contain CCAP. We are currently using the antibody to identify CCAP containing neurons of the last instar larvae of the corn earworm, Helicoverpa zea, and the pupal stage of the yellow mealworm, Tenebrio molitor. The identified neurons are similar to what has been published with other Lepidoptera and Coleoptera. We are currently trying to determine the intensity of the immunostaining in comparisons between acetone-treated and neonicotinoid-treated larvae and pupae. So far it appears that the staining intensity decreases post ecdysis in the mealworm, as expected due to the CCAP being released and degraded. In mealworms, it also appears that the neonicotinoid treatment does not reduce the CCAP levels in the nervous system, indicating that the insecticide treatment interferes with the release of CCAP thus causing AE. We have also utilized an antibody that detects a peptide that starts the ecdysis process, ecdysis triggering hormone, and have shown that it is being released to start ecdysis in both acetone and insecticide treatments. An antibody targeting GABA has also been utilized to identify the GABA producing neurons. So far this has shown that many neurons produce GABA, making it difficult to pinpoint specific neurons that could potentially be involved in AE. We have undertaken preliminary tests with bursicon antibody (burscion peptides are also released by CCAP neurons) in corn earworms. Results indicate bursicon release is significantly different between control and neonicotinoid-treated larvae; however, more data are needed to validate these findings. Under Objective d, we have topically treated all three beetle species with additional compounds outside of imidacloprid. These include sulfoxaflor, acetamiprid, thiacloprid, beta-cyfluthrin, cypermethrin, and permethrin. Acetamiprid was the most effective at causing AE. Type II pyrethroids (beta-cyfluthrin and cypermethrin) are more effective at causing AE than type I pyrethroids (permethrin). Thus, our hypothesis has been modified to include both acetylcholine and GABA as potential regulators of CCAP neurons.Results for Drosophila and housefly (imidacloprid treatments) were obtained previously.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Jurenka RA, Adeyanju O, Bradbury SP, Gorman CL, Krishnan N. Neonicotinoids and pyrethroids can cause arrested ecdysis in Coleoptera. Entomological Society of America, National Harbor, MD.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Stewart J, Bradbury S, Jurenka R, Krishnan N. Evaluating the effect of neonicotinoid insecticides on insect ecdysis movements. Eastern Branch Entomological Society of America, Morgantown, WV.
- Type:
Journal Articles
Status:
Other
Year Published:
2024
Citation:
(About to be submitted within two weeks)
Krishnan N, Gorman C#, Stewart J#, Bradbury SP, Jurenka RA. Using insecticidal compounds to elucidate the potential roles of acetylcholine and gamma-aminobutyric acid in Lepidoptera pupal ecdysis. Scientific Reports.
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