Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.
Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
Eicosanoids mediate insect cellular immune reactions to bacterial infections
Abstract
A line of experiments designed to test the hypothesis that eicosanoids mediate insect microaggregation and nodulation reactions to bacterial infections were conducted on six different insect species including the tobacco hornworm, Manduca sexta, the tenebrionid beetle, Zophobas atratus, true armyworm, Pseudaletia unipuncta, black cutworm, Agrotis ipsilon, silkworm, Bombyx mori, and the adult cricket, Gryllus assimilis. Treating insects with the eicosanoid biosynthesis inhibitor, dexamethasone, just prior to infection strongly reduced nodulation responses to bacterial infections. The dexamethasone effects were expressed in a dose-dependent manner, and were reversed by treating infected insects with eicosanoid-precursor polyunsaturated fatty acids. Treatments with the saturated fatty acid, 16:0, which is not an eicosanoid precursor, did not reverse the dexamethasone effects on nodulation. Nodulation intensity, as measured by numbers of nodules was tightly related to bacterial dosages in M. sexta and Z. atratus. In medium and large Z. atratus larvae, as well as fifth stage M. sexta larvae, a greater number of nodules are formed in response to increased bacterial challenges. A similar pattern emerged from experiments with medium and large size Z. atratus larvae. Experiments designed to test the influence of bacterial species on nodulation intensity for M. sexta and for Z. atratus show variation in number of nodules formed in response to similar challenges with four bacterial species, Serratia marcescens, Sarcina flava, Escherichia coli, Bacillus subtilis. Serratia marcescens and S. flava induced high levels of nodulation in Manduca and Zophobas. Escherichia coli induced lower levers of nodulation in Manduca. Bacillus subtilis induced very little nodulation in Manduca and in Zophobas. Zophobas atratus and M. sexta exhibit different capacities to form nodules in response to similar bacterial challenges and the nodules observed in both species were discreet formations of approximately the same size. The possibility that nodulation is related to the age and size of the insects was considered. Results indicate that the nodulation response occurs in all larval stages examined. However, nodulation intensity is unrelated to either insect biomass or body length.
Subject Area
Entomology|Molecular biology|Anatomy & physiology|Animals
Recommended Citation
Miller, Jon Scott, "Eicosanoids mediate insect cellular immune reactions to bacterial infections" (1998). ETD collection for University of Nebraska-Lincoln. AAI9908477.
https://digitalcommons.unl.edu/dissertations/AAI9908477