Hosokawa Takahiro, Kikuchi Yoshitomo, Meng Xien Ying, Fukatsu Takema
Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology AIST, Tsukuba 305-8566, Japan.
FEMS Microbiol Ecol. 2005 Nov 1;54(3):471-7. doi: 10.1016/j.femsec.2005.06.002. Epub 2005 Jul 21.
In stinkbugs of the family Plataspidae, adult females deposit small brownish particles, containing specific symbiotic bacteria inside, on the underside of their egg mass. Newborn nymphs ingest the content of the unique structure, called "symbiont capsule", whereby vertical transmission of the symbiont occurs. We investigated the fine structure and the formation process of the symbiont capsule in the Japanese common plataspid stinkbug, Megacopta punctatissima, by using light and electron microscopy. It was demonstrated that (i) the capsule consists of three structural components, namely "symbionts", "matrix" and "envelope"; (ii) the posterior midgut of adult females is characterized by several specific sections with peculiar anatomical traits, including "thin crypt-bearing midgut (TCM) section", "swollen crypt-bearing midgut (SCM) section" and "brownish enlarged midgut (BEM) end section"; (iii) the different capsule components, symbionts, matrix and envelope, are produced and/or supplied by the specialized midgut sections, TCM, SCM and BEM, respectively; and (iv) the capsule components are stored in BEM and excreted during oviposition to produce the symbiont capsules. These results strongly suggested that the host insect incurs a substantial cost for the symbiont transmission. Ecological and evolutionary implications of the highly developed, female-specific system for symbiont transmission were discussed.
在扁盾蝽科的椿象中，成年雌性会在卵块的下侧产下小的褐色颗粒，这些颗粒内部含有特定的共生细菌。新生若虫摄取这种独特结构（称为“共生体胶囊”）的内容物，从而实现共生体的垂直传播。我们利用光学显微镜和电子显微镜研究了日本常见扁盾蝽（Megacopta punctatissima）中共生体胶囊的精细结构和形成过程。结果表明：（i）胶囊由三个结构成分组成，即“共生体”“基质”和“包膜”；（ii）成年雌性的中肠后部有几个具有特殊解剖特征的特定部分，包括“含薄隐窝中肠（TCM）部分”“含肿胀隐窝中肠（SCM）部分”和“褐色扩大中肠（BEM）末端部分”；（iii）不同的胶囊成分，共生体、基质和包膜，分别由专门的中肠部分TCM、SCM和BEM产生和/或提供；（iv）胶囊成分储存在BEM中，并在产卵时排出以形成共生体胶囊。这些结果有力地表明宿主昆虫为共生体传播付出了巨大代价。我们还讨论了这种高度发达的、雌性特有的共生体传播系统的生态和进化意义。
