Nano-injection method for micro-insects without sedation using the western flower thrips, Frankliniella occidentalis

Authors: RAFFIN, CATHERINE - Oregon State University; Price, Briana; YUN, SEUNG HWAN - Agricultural Research And Extension Service, Korea; Choi, Man-Yeon

Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2022
Publication Date: 8/3/2022
Citation: Raffin, C., Price, B.E., Yun, S., Choi, M.Y. 2022. Nano-injection method for micro-insects without sedation using the western flower thrips, Frankliniella occidentalis. Journal of Applied Entomology. 146(9):1200-1206. https://doi.org/10.1111/jen.13063.
DOI: https://doi.org/10.1111/jen.13063

Interpretive Summary: Western flower thrips (WFT) is a common horticultural and nursery crop pest throughout the world. Due to their extremely small size and broad host range, detecting and preventing the spread of WFT is extremely difficult. WFT damages plant matter by feeding and indirectly vectoring plant pathogenic viruses. In this study, we developed a novel nano-injection system and protocol for micro-insects (< 3 mm) using the thrips model. We found a suitable injection site with minimal injury to the thrips, resulting in decreased physiological stress on the insects. Our method will facilitate injection bioassay with biological compounds into micro-live insects without any immobilization tools.

Technical Abstract: Micro-injection techniques are invaluable in entomological research as they allow for the direct delivery of biological compounds into the hemocoel of specimens at controlled volumes. Nearly all micro-injection methods (> 4 mm in size) utilize forcibly immobilized insects that could affect specimen fitness and physiology. This alteration can cause inconclusive interpretation of phenotypic reactions post-injection. In this study, we detail a novel, improved nano-volume injection technique for micro-insects (< 3 mm) using the western flower thrips, Frankliniella occidentallis as a model. By constructing and using a modified vacuum stand, injections were performed on live thrips, without sedation and physical injury. A simple survivorship assay in which the thrips were injected with 10 nl water into the thorax or abdomen demonstrated that thoracic injections yield similar survival rates to control thrips that were not injected, while abdominal injections severely limited survivorship. Here we present the integrative method that customizes the vacuum stand, nano-injection tools, injecting volume, and other specifications for live micro-insects.