How many symbionts are provided by mothers, acquired by offspring, and needed for successful vertical transmission in an obligate insect-bacterium mutualism?

Takahiro Hosokawa, Yoshitomo Kikuchi, Takema Fukatsu

Research output: Contribution to journalArticlepeer-review

53 Citations (Scopus)

Abstract

Vertical symbiont transmission is among the most pivotal processes for maintenance of symbiotic associations. However, it is poorly understood whether and how the levels of resource allocation and investment upon vertical transmission are regulated. The stinkbug Megacopta punctatissima is obligatorily associated with the gut symbiotic bacterium 'Candidatus Ishikawaella capsulata', whose transmission is mediated by a unique mechanism called 'symbiont capsule'. We investigated the population dynamics of the symbiont during vertical transmission in the host-symbiont mutualism. The stinkbug mothers produced one capsule for around 3.6 eggs irrespective of clutch size, suggesting a strict maternal control over symbiont supply for the offspring. However, experimental manipulation of egg/capsule ratios revealed that one capsule is sufficient for symbiont transmission to six nymphs. Quantitative polymerase chain reaction analyses demonstrated that a capsule contains 1.2 × 108 symbionts, a newborn nymph possesses 2 × 10 7 symbionts from a capsule, and thus one capsule certainly contains a sufficient amount of symbiont cells for six nymphs. These results indicated that the stinkbug mothers produce 1.7 times more symbiont capsules than needed. The newborn nymphs consistently harboured around 2 × 107 symbionts, also suggesting a nymphal control over symbiont transmission. The threshold symbiont titre minimally needed for successful vertical transmission was estimated to be 1.9 × 106 symbionts, which is only 1/10 of the actual symbiont titre detected in a newborn nymph. These results illuminate several ecological factors that may be relevant to parental and offspring controls over symbiotic resource allocation through host insect generations.

Original languageEnglish
Pages (from-to)5316-5325
Number of pages10
JournalMolecular Ecology
Volume16
Issue number24
DOIs
Publication statusPublished - Dec 1 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Genetics

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