University of the Ryukyus · Tropical Biosphere Research Center · 助教

Research keywords昆虫・進化・冬虫夏草・寄生・共生・腸内細菌・胚発生・細菌・細胞内共生・真菌

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• Caballeronia Gut Symbionts in Species of the Seed Bug Family Heterogastridae (Heteroptera: Lygaeoidea).2025 · <p>Most phytophagous species of stinkbugs have mutualistic relationships with bacterial symbionts, which are often located within specialized midgut regions called M4. Heterogastridae, previously classified within the family Lygaeidae, are now classified as a family proper; however, the symbiotic organ’s morphology and symbiont identity remain unclear. We herein investigated symbiotic systems from two heterogastrid species. The results obtained show that they possess two rows of midgut crypts akin to those of Coreoidea and consistently associate with <i>Caballeronia</i> symbionts of the SBE-α and Coreoidea clades. The present study clearly demonstrates that <i>Caballeronia</i> bacteria are symbionts of Heterogastridae and is the first to report a Coreoidea clade symbiont from the superfamily Lygaeoidea.</p>
• Dual mitochondrial haplotypes and nuclear genotypes of solanum fruit fly Bactrocera latifrons (Diptera: tephritidae) from Ryukyu Islands indicate multiple origins and inter-strain breeding of the invasive species in Japan2025 · Hisaoka, T; Sekine, R; Matsuyama, T; Huang, YB; Itoh, H; Takakura, KI; Nishida, T; Honma, A; Matsuura, Y
• The facultative intracellular symbiont Lariskella is neutral for lifetime fitness and spreads through cytoplasmic incompatibility in the leaffooted bug, Leptoglossus zonatus.2025 · The maternally-inherited, intracellular bacterium Lariskella (Alphaproteobacteria: Midichloreaceae) has been widely detected in arthropods including true bugs, beetles, a wasp, a moth, and pathogen-vectoring fleas and ticks. Despite its prevalence, its role in the biology of its hosts has been unknown. We set out to determine the role of this symbiont in the leaffooted bug, Leptoglossus zonatus (Hempitera: Coreidae). To examine the effects of Lariskella on bug performance and reproduction as well as in possible interactions with the bug's obligate nutritional symbiont, Caballeronia, bugs were reared in a factorial experiment with both Lariskella and Caballeronia positive and negative treatments. Lifetime survival analysis (~120 days) showed significant developmental delays and decrease in survival for bugs that lacked Caballeronia, and Caballeronia-free bugs did not reproduce. However, among the Caballeronia carrying treatments, there were no significant differences in lifetime survival or reproduction in treatments with and without Lariskella, suggesting this symbiont is neutral for overall bug fitness. To test for reproductive manipulation, crossing among Lariskella-positive and negative individuals was performed. When Lariskella-negative females were mated with Lariskella positive males, fewer eggs survived early embryogenesis, consistent with a cytoplasmic incompatibility (CI) phenotype. Wild L. zonatus from California and Arizona showed high but not fixed Lariskella infection rates. Within individuals, Lariskella titer was low during early development (1st-3rd instar), followed by an increase that coincided with development of reproductive tissues. Our results reveal Lariskella to be among a growing number of microbial symbionts that cause CI, a phenotype that increases the relative fitness of females harboring the symbiont. Understanding the mechanism of how Lariskella manipulates reproduction can provide insights into the evolution of reproductive manipulators and may eventually provide tools for management of hosts of Lariskella, including pathogen-vectoring ticks and fleas.
• A potential risk and management of feces in the queenless ant2024 · Ishizuka, Y; Yamashita, R; Itoh, H; Matsuura, Y; Kikuchi, Y; Shimoji, H

• 昆虫寄生菌から絶対共生菌はどのように進化したのか2024 · 基盤研究(B)（一般）
• 自然免疫と内部共生の境界線を探る -非自己の許容がもたらす細胞内共生の進化-2019 · 基盤研究(B)
• 全地球規模で解き明かすカメムシ共生細菌の多様性と進化2018 · 本研究全体を通して、国内に生息しないために未調査のままとなっているカメムシ下目の25科をターゲットに絞りその共生様式の世界的調査を行う。具体的には共生器官の形態や共生細菌の局在性、共生細菌の系統分類を行い、現地で飼育が可能な場合には共生細菌の伝播様式および適応度効果の調査を行う。また共生細菌のゲノム解読を行い、それらカメムシ類における共生細菌の具体的な機能について推定を行う。同時に宿主カメムシ自身についてもミトコンドリアゲノムの解読を行い、カメムシ下目内における各グループ間の系統関係について推定を進め、そこに調査から明らかとなった共生様式をプロットすることで、カメムシ下目内においてどのように多様な内部共生系が進化してきたのか網羅的に明らかにすることを目的とする。参画する2名の若手研究者が中心となり新規カメムシ類の調査を行い、また大学院生の参画を積極的に促し、当該分野における次々世代の育成にも引き続き注力する。得られた研究成果について国際誌への投稿を行うとともに国際学会にて発表を行い、成果の発信と新たな共同研究者の開拓を目指す。初年度に当たる本年は、主要共同研究先である米国アリゾナ大学のMartha Hunter教授との連携体制を深める目的でアリゾナ大学を訪問し、研究進捗や今後の計画について議論を行った。Hunter研究室ではすでにヘリカメムシ類やイトカメムシ類の飼育実験が進められており、日本側で進められている研究内容との比較を行うとともに、今後の方向性や米国におけるカメムシ採集計画について深い議論を行うことができた。また、研究協力の体制についても議論を行い、今後共同研究を進める上での基盤を構築することができた。
• ミバエ類の腸内細菌が土壌環境の改変により寄主植物に与える影響の解明2018 · 挑戦的研究(萌芽)

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