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Biological and molecular characterization of caecum-associated symbionts in the Pentatomidae

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Title:Biological and molecular characterization of caecum-associated symbionts in the Pentatomidae
Authors:Prado, Simone S.
Date Issued:2008
Description:Thesis (Ph.D.)--University of Hawaii at Manoa, 2008.
The Pentatomidae is one of the largest families within the suborder Heteroptera (order Hemiptera), with over 4000 described species within eight subfamilies. Stink bugs are major pests of economically important crops worldwide including soybeans, rice, pecan, cocoa and macadamia nuts. Relationships between microorganisms and insects have been previously studied, but the majority of these associations remain poorly understood. In this dissertation I present molecular data showing that Nezara viridula, Acrosternum hilare Murgantia histrionica, Euschistus heros, Chlorochroa ligata, C. sayi, C. uhleri, Plautia stali and Thyanta pallidovirens harbor a common dominant caecum-associated bacterial symbiont in their midgut. I also show that oral rather than transovarial transmission occurs by detecting the symbiont on eggshells after nymphs had hatched, instead of detecting symbionts in female ovarioles. Additionally, I demonstrated that these symbionts are polyphyletic suggesting that replacement of the symbiont may occur over time. Phylogenetic placement showed the pentatomid symbionts were associated with the plant pathogens Erwinia and Pantoea. Using a demographic approach I analyzed the effect of egg masses surface sterilization and temperature on the symbiont maintenance and on insect development of the pentatomids N. viridula, A. hilare and M. histrionica. Here I demonstrate that maintenance of the symbiont was affected by high temperature and egg mass surface sterilization for the species N. viridula, A. hilare and M. histrionica. N. viridula's reproduction parameters were not significantly different between the surface sterilized and control treatments at three temperatures, however no reproduction was observed at 20°C of the surface sterilized treatment. Survivorship and reproductive parameters for A. hilare were negatively affected by surface sterilization of egg masses and for higher temperatures. Conversely, no effect was observed for M. histrionica. Curiously, M. histrionica had lower rates of positive insects for the symbiont at 25°C than A. hilare. Here I suggest that the degree of mutualism of this association for pentatomid species is variable, given the fact that A. hilare requires its symbiont for adequate development, while M. histrionica's symbiont may not be significant in development of the host insect and N. viridula is not affected by deprivation of its gut-associated symbiont.
Includes bibliographical references (leaves 133-136).
Also available by subscription via World Wide Web
146 leaves, bound 29 cm
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Entomology

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