Functional foregut anatomy of the blue–green sharpshooter illustrated using a 3D model

Abstract

Sharpshooter leafhoppers (Hemiptera: Cicadellidae: Cicadellinae) are important vectors of the plant pathogenic bacterium Xylella fastidiosa Wells et al. (Xanthomonadales: Xanthomonadaceae). This pathogen causes economically significant diseases in olive, citrus, and grapes on multiple continents. Bacterial acquisition and inoculation mechanisms are linked to X. fastidiosa biofilm formation and fluid dynamics in the functional foregut of sharpshooters, which together result in egestion (expulsion) of fluids likely carrying bacteria. One key X. fastidiosa vector is the blue–green sharpshooter, Graphocephala atropunctata (Signoret, 1854). Herein, a 3D model of the blue–green sharpshooter functional foregut is derived from a meta-analysis of published microscopy images. The model is used to illustrate preexisting and newly defined anatomical terminology that is relevant for investigating fluid dynamics in the functional foregut of sharpshooters. The vivid 3D illustrations herein and supplementary interactive 3D figures are suitable resources for multidisciplinary researchers who may be unfamiliar with insect anatomy. The 3D model can also be used in future fluid dynamic simulations to better understand acquisition, retention, and inoculation of X. fastidiosa. Improved understanding of these processes could lead to new targets for preventing diseases caused by X. fastidiosa.

Fluid dynamic simulations at the interface of the blue-green sharpshooter functional foregut and grapevine xylem sap with implications for transmission of Xylella fastidiosa

“…fastidiosa transmission, both acquisition and inoculation [ 6 ]. Simulation results are plotted as colormaps within 3D molds [ 20 ] that resemble segments of the two halves of the precibarium, the epipharynx and hypopharynx ( Fig 3 ). The colormaps represent the calculated drag force experienced by an individually surface-attached bacterium at a given location.…”

“…The number labels are present to highlight the location of insect anatomy within the precibarium that are further described in text. See White, et al, [ 20 ] for full description of each segment of the precibarium.…”

“…During G . atropunctata probing, xylem fluids are taken up by cibarial pumping through the stylet tips, into the stylet food canal, through the precibarium, the cibarium (together, the functional foregut; anatomy shown in Fig 1 , [ 20 ]), then ingested via swallowing through the true mouth at the proximal end of the cibarium. Technically, ingestion does not occur until the fluid is swallowed.…”

“…The scissors and dotted lines indicate where the 3D model in subfigure a would be split to obtain the 3D model segments in subfigures b and c. The associated black curved arrows in subfigure a indicate that the two halves of the split 3D model segment would need to be hinged outward to obtain the views in subfigures b and c. The gray 3D parts of subfigures b and c are semi-abstract representations of the epipharynx and hypopharynx that serve for comparison with their corresponding electron microscope images. (Previously published figure from White, et al [ 20 ] is reprinted here under the Creative Commons Attribution 4.0 International License).…”

“…Here, we simulated precibarial fluid dynamics during egestion using a 3D model of the G . atropunctata precibarium [ 20 ] appropriate for nuanced drag force predictions. Precibarial fluid dynamics during ingestion were also simulated to gain understanding about X .…”