New and simple methods for studying Hemipteran stylets, bacteriomes and salivary sheaths in host plants

Authors: Ammar, Eldesouky; Hall, David

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2012
Publication Date: 2/12/2013
Citation: Ammar, E., Hall, D.G. 2013. New and simple methods for studying Hemipteran sytlets, bacteriomes and salivary sheaths in host plants. Annals of the Entomological Society of America. 105(5):731-739. 2013. Available: http://dx.doi.org/10.1603/AN12056.

Interpretive Summary: Many hemipteran insects are important agricultural pests because they cause direct feeding damage to their host plants and/or because they transmit plant disease agents including viruses and bacteria. Here, we describe new and simple methods that include the use of exuviae (molted skins) to study the ultrastructure of stylets and other mouth parts in various nymphal instars, a simpler method for studying the salivary sheaths in host plants, and the use of autofluorescence to localize the bacteriome (organ containing symbiotes) in hemipteran eggs and nymphs. The above methods were applied successfully with five species from four families, including psyllids, aphids, whiteflies and leafhoppers. Additionally, we provide evidence from the five species studied that hemipteran nymphs use their stylets to anchor themselves to their host plants during ecdysis.

Technical Abstract: Many hemipteran insects are important agricultural pests because they cause direct feeding damage to their host plants and/or because they transmit plant disease agents including viruses and bacteria. Microscopic and behavioral studies on five hemipteran species from four families (Psyllidae, Aphididae, Cicadellidae, and Aleyrodidae) showed that their exuviae normally had either fully or partially extended stylets in a feeding-like position. In most cases these stylets were still partially embedded in their host plants after ecdysis, which indicated that plant-feeding hemipteran nymphs use their stylets to anchor themselves to host plants during molting. This phenomenon was used here to study the stylet length and ultrastructure in various instars, which is normally more difficult in nymphs than in adults because of the fragility and smaller size of nymphs. Additionally, autofluorescence was used for studying the hemipteran salivary sheaths of nymphs and adults in their host plants. This method is based on fixation of free hand sections of the plant parts on which hemipteran insects have been feeding, then mounting and examination of these sections with epifluorescence or confocal microscopy. No embedding, microtomy or staining is necessary for this method which makes it much faster and simpler than other methods. Autofluorescence was also used to study the location and size of bacteriomes/ mycetomes (organs containing symbiotes) in hemipteran eggs and nymphs. The above methods were applied successfully with the Asian citrus psyllid (Diaphorina citri), melaleuca psyllid (Boreioglycaspis melaleucae), oleander aphid (Aphis nerii), the whitefly Bemisia tabaci, and the glassy-winged sharpshooter leafhopper (Homalodisca vitripennis).