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- Title
A Nightmare for Males? A Maternally Transmitted Male-Killing Bacterium and Strong Female Bias in a Green Lacewing Population.
- Authors
Hayashi, Masayuki; Watanabe, Masaya; Yukuhiro, Fumiko; Nomura, Masashi; Kageyama, Daisuke
- Abstract
For maternally transmitted microbes, a female-biased host sex ratio is of reproductive advantage. Here we found a strong female bias in a field population of the green lacewing, Mallada desjardinsi (Insecta; Neuroptera). This bias was attributed to the predominance of individuals harboring a maternally inherited male-killing bacterium that was phylogenetically closely related to the plant-pathogenic Spiroplasma phoeniceum and Spiroplasma kunkelii. Among 35 laboratory-reared broods produced by wild-caught females, 21 broods (60%)—all infected with Spiroplasma—consisted of only females (940 individuals). Among 14 broods consisting of both males and females (516 and 635 individuals, respectively), 4 broods were doubly infected with Spiroplasma and Rickettsia, 6 broods were singly infected with Rickettsia, and 3 broods were uninfected (remaining one brood was unknown). Mortality during embryonic and larval development was prominent in all-female broods but not in normal sex ratio broods. Following antibiotic treatment on all-female broods, mortality was significantly reduced and the sex ratio was restored to 1:1. Strong expression and high prevalence of this male-killer is remarkable considering its low density (~10−5–10−4 cells per host mitochondrial gene copy based on quantitative PCR). In addition, a bacterium closely related to Rickettsia bellii was present in 25 of 34 broods (73.5%), irrespective of the sex ratio, with the infection density comparable to other cases of endosymbiosis (~10−2–10−1 cells per mitochondrial gene copy). Higher density of Rickettsia than Spiroplasma was also demonstrated by electron microscopy which visualized both Spiroplasma-like cells and Rickettsia-like cells inside and outside the ovarian cells.
- Subjects
CHRYSOPIDAE; LACEWINGS; NEUROPTERA; INSECTS; SPIROPLASMAS
- Publication
PLoS ONE, 2016, Vol 11, Issue 6, p1
- ISSN
1932-6203
- Publication type
Article
- DOI
10.1371/journal.pone.0155794