The making of symbiont capsule in the plataspid stinkbug Megacopta punctatissima

Authors

  • Takahiro Hosokawa,

    Corresponding author
    1. Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305–8566, Japan
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  • Yoshitomo Kikuchi,

    1. Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305–8566, Japan
    2. Natural History Laboratory, Faculty of Science, Ibaraki University, Mito 310–8512, Japan
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  • Xien Ying Meng,

    1. Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305–8566, Japan
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  • Takema Fukatsu

    1. Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305–8566, Japan
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*Corresponding author. th-hosokawa@aist.go.jp

Abstract

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.

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