ARS | Publication request: Muscle movements that control inoculation of Xylella fastidiosa are revealed by head X-rays of feeding glassy-winged sharpshooters

Submitted to: Entomological Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: September 30, 2010
Publication Date: November 1, 2010
Citation: Backus, E.A., Lee, W., Socha, J., Lee, E. 2010. Muscle movements that control inoculation of Xylella fastidiosa are revealed by head X-rays of feeding glassy-winged sharpshooters. Entomological Society of America Annual Meeting, Dec 12-15, 2010, San Diego, CA. Available: http://esa.confex.com/esa/2010/webprogram/Paper50391.html.

Technical Abstract: The mechanism of inoculation of the Pierce’s disease bacterium, Xylella fastidiosa (Xf), by vectors such as the glassy-winged sharpshooter (GWSS) is still unknown, despite nearly 70 years of study. Research in support of the egestion-salivation hypothesis for Xf inoculation is presented. Two important steps in this hypothesis are: 1) uptake of saliva into the vector’s precibarium, causing attached Xf bacteria therein to loosen from the cuticle, followed by 2) expulsion (egestion) of saliva containing loosened bacteria into the xylem prior to ingestion. To directly observe actions of cibarial muscles controlling ingestion (uptake) and egestion of fluid from the precibarium, live, feeding GWSS were X-rayed and video-recorded in the Advanced Photon Source at the Argonne National Laboratory. Simultaneously, feeding of X-rayed sharpshooters was recorded using AC/DC Electrical Penetration Graph (EPG) technology. Cibarial muscles were observed to be attached to two sets of tracheae (air tubes) inside the head. The tracheae moved at different times during feeding, clearly indicating muscle movement. Video indicated rhythmic pulsing of tracheae was correlated with EPG-waveform C2, whereas abrupt non-rhythmic tracheal movements were correlated with EPF-waveform C1. In addition, gentle fluttering of ventral tracheae was correlated with waveform B1. Results support that B1 is correlated with uptake of small amounts of fluid, presumably into the precibarium alone; C1 is correlated with rapid, discharging egestion from the cibarium; and C2 is correlated with uptake of large amounts of fluid into the precibarium and cibarium, for ingestion (swallowing).