ABSTRACT
Contents Introduction.......................................................................................................................... 96 Gut bacterial symbiosis in stinkbugs ............................................................................... 97 Stinkbugs of the family Plataspidae ................................................................................. 97 Scientic history: discovery of symbiont capsule in plataspid stinkbug .................... 97 Personal history: why has plataspid symbiosis fascinated us? ....................................98 Symbiotic system of the Japanese common plataspid stinkbug Megacopta punctatissima .........................................................................................................................99 Posterior midgut of plataspid stinkbug as specialized symbiotic organ .................. 103 Laboratory rearing of plataspid stinkbugs .................................................................... 104 Prevalence of maternal capsule production in plataspid stinkbugs .......................... 104 Phylogenetic placement of plataspid symbionts ........................................................... 105 Production of symbiont-free insects by removal of capsules ..................................... 105 Effects of symbiont infection on host tness and phenotype ..................................... 106 Essential role of gut symbionts for host stinkbug ........................................................ 107 Host-symbiont cospeciation despite the midgut extracellular symbiosis ................ 108 General patterns in the genome evolution of endocellular symbiotic bacteria of insects .................................................................................................................................. 109 Reductive genome evolution in the midgut extracellular symbiotic bacteria .......... 110 Proposal of “Candidatus Ishikawaella capsulata” ......................................................... 110 Plataspid-Ishikawaella symbiosis: a novel model system for insect symbiosis studies ................................................................................................................................. 110 Symbiont acquisition alters behavior of nymphal stinkbugs...................................... 112
Effects of parasitic symbiont on host behavior and biology .................................. 112 Effects of mutualistic symbiont on host behavior and biology ............................. 112 Resting/aggregating behavior of stinkbug nymphs ............................................... 112 Nymphal resting behavior in M. punctatissima ........................................................ 113 Experimental depletion of symbiont resulted in nymphal wandering behavior .......................................................................................................................... 113 Lower symbiont supply resulted in more wandering nymphs ............................. 113 Wandering nymphs were certainly symbiont-depleted ......................................... 113
Insights into behavioral biology of symbiont-associated insects .......................... 114 Pest status of host stinkbugs is determined by their gut symbiotic bacteria ........... 115
Closely related pest and nonpest plataspid stinkbugs ............................................ 115 What differs between pest and nonpest stinkbugs? ............................................... 115 Experimental symbiont exchange between pest and nonpest stinkbugs ............ 115 Pest became nonpest and nonpest became pest after symbiont exchange .......... 117 Pest status of stinkbug determined by symbiont genotype ................................... 117 Insights into pest evolution, control, and management .......................................... 118
Conclusion and perspective ............................................................................................. 118 Acknowledgments ............................................................................................................. 119 References ........................................................................................................................... 119
Introduction Symbiotic microorganisms are universally found in the gut, body cavity, or cells of a wide variety of insects. Some obligate symbionts are of a mutualistic nature and contribute to the tness of their hosts, whereas other facultative symbionts are rather parasitic and tend to cause negative effects on their hosts (Bourtzis and Miller, 2003, 2006).
