The most extraordinary systems of symbiosis in insects are found in the suborder Auchenorrhyncha of Hemiptera, which provide unique perspectives for uncovering complicated insect-microbe symbiosis. We investigated symbionts associated with bacteriomes and fat bodies in six cicada species, and compared transmitted cell number ratio of related symbionts in ovaries among species. We reveal that Sulcia and Hodgkinia or a yeast-like fungal symbiont (YLS) are segregated from other host tissues by the bacteriomes in the nymphal stage, then some of them may migrate to other organs (i.e., fat bodies and ovaries) during host development. Particularly, YLS resides together with Sulcia in the “symbiont ball” of each egg and the bacteriomes of young-instar nymphs, but finally migrates to the fat bodies of adults in the majority of Hodgkinia-free cicadas, whereas it resides in both bacteriome sheath and fat bodies of adults in a few other species. The transmitted Sulcia/YLS or Sulcia/Hodgkinia cell number ratio in ovaries varies significantly among species, which could be related to the distribution and/or lineage splitting of symbiont(s). Rickettsia localizes to the nuclei of bacteriomes and fat bodies in some species, but it was not observed to be transmitted to the ovaries, indicating that this symbiont may be acquired from environments or from father to offspring. The considerable difference in the transovarial transmission process of symbionts suggests that cellular mechanisms underlying the symbiont transmission are complex. Our results may provide novel insights into insect-microbe symbiosis.

中文翻译：

---

蝉复杂共生系统中内共生体的分离为食液昆虫的微生物共生和共生器官的进化动力学提供了新的见解


昆虫中最非凡的共生系统是在半翅目真喙亚目中发现的，它为揭示复杂的昆虫-微生物共生关系提供了独特的视角。我们研究了六种蝉物种中与细菌组和脂肪体相关的共生体，并比较了物种间卵巢中相关共生体的传播细胞数比率。我们发现，Sulcia 和 Hodgkinia 或类似酵母的真菌共生体（YLS）在若虫阶段通过细菌组与其他宿主组织分离，然后其中一些可能在宿主发育过程中迁移到其他器官（即脂肪体和卵巢） 。特别是，YLS 与 Sulcia 一起存在于每个卵的“共生球”和幼龄若虫的细菌组中，但最终迁移到大多数无霍奇金蝉的成虫脂肪体中，而它同时存在于两个细菌组鞘中以及其他一些物种的成虫的脂肪体。卵巢中传播的 Sulcia/YLS 或 Sulcia/Hodgkinia 细胞数量比率在物种之间存在显着差异，这可能与共生体的分布和/或谱系分裂有关。在某些物种中，立克次体定位于细菌组和脂肪体的细胞核，但没有观察到它被传播到卵巢，这表明这种共生体可能是从环境中获得的，或者是从父亲传给后代的。共生体跨卵巢传播过程的巨大差异表明共生体传播背后的细胞机制是复杂的。我们的结果可能为昆虫-微生物共生提供新的见解。