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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Commodity Protection and Quality Research » Research » Publications at this Location » Publication #303656

Title: Egg morphology and chorionic ultrastructure of key stored product insect pests of the United States

item GAUTAM, SANDIPA - Oklahoma State University
item OPIT, GEORGE - Oklahoma State University
item Margosan, Dennis
item HOFFMANN, DARLENE - Retired ARS Employee
item Tebbets, John
item Walse, Spencer

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2014
Publication Date: 12/30/2014
Citation: Gautam, S., Opit, G., Margosan, D.A., Hoffmann, D., Tebbets, J.S., Walse, S.S. 2014. Egg morphology and chorionic ultrastructure of key stored product insect pests of the United States. Annals of the Entomological Society of America. 108(1):43-56.

Interpretive Summary: Postharvest chamber fumigation of commodities provides a biological safeguard against pests and, in many scenarios, is the only available tool for government and industry to guarantee pest-free commodities for quarantine and trade. In general, the eggs are the most difficult life stage of insects to control with fumigants. This research explored species-specific differences between egg surfaces as part of an attempt to relate these differences to the relative ovicidal efficacies of fumigants. Results suggest that fumigant efficacy is related, at least in part, to the number of respiratory structures on an egg's surface and the structural composition of the chorion layers comprising the egg surface. These results will enable better control of insects in stored products by providing better understanding of how fumigants work and how fumigants can be engineered to be more effective.

Technical Abstract: Eggs of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) were imaged with scanning electron microscopy to explore how respiratory openings on the chorion surface may be related to the efficacy of fumigants. Each P. interpunctella egg had many aeropyles and several micropyles, whereas each T. castaneum egg had neither aeropyles nor micropyles. Transmission electron microscopy was used to obtain cross sectional images of chorions, with eggs of T. castaneum, P. interpunctella, Carpophilus hemipterus (L.) (Coleoptera: Nitidulidae), and Amyelois transitella (Lepidoptera: Pyralidae) each having unique chorionic structure. The types of layers and relative thicknesses of different layers of the chorion varied across species. Exochorion of lepidopteran eggs was a lamellate structure and the thickest layer, whereas crystalline endochorion was the thickest layer in coleopterans. Although quantitative data on fumigant uptake by eggs of different insect species are needed, the findings of the current study suggest that species-specific tolerance of eggs to fumigants may partly be explained by differences in respiratory structures and chorion characteristics.