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The phylogeny of the bacterial endosymbionts found in Phasmatodea shows three main phyla: Proteobacteria (classes α, β and γ), Actinobacteria and Firmicutes. Spiroplasma spp. be- longs to the latter phylum.
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The ecological and genetic mechanisms that determine Phasmatodea reproductive biology are poorly understood. The Order includes standard sexual species, but also many others that display distinct types of parthenogenesis (tychoparthenogenesis, automixis, apomixis, etc.), or both systems facultatively. In a preliminary survey, we analysed Wolbachia...
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Introduction:
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Citations
... Determination of P. elongatus parthenogenesis mechanisms will require cytological observations or detailed mother-offspring microsatellite analysis focusing on recombination, wherein the markers presented in the current study will be an essential tool. The effect of sex-manipulating bacteria, such as Wolbachia and Spiroplasma, might also be considered in future studies, although it is unlikely to arise in stick insects (Pérez-Ruiz et al., 2015). Overall, we successfully developed 13 microsatellite markers for P. elongatus, and these markers were sufficient for population genetic analysis of this species. ...
Many plant and animal species exhibit geographic parthenogenesis, wherein unisexual (= parthenogenetic) lineages are more common in their marginal habitats such as high latitude or altitudes than their closely related bisexual counterparts. The Japanese stick insect, Phraortes elongatus (Thunberg) (Insecta: Phasmatodea), is known as a geographically parthenogenetic species due to the existence of both bisexual and unisexual populations. Here, we developed microsatellite markers to infer the genetic variation among populations of P. elongatus. Totally, 13 primer pairs were developed for the species, and they were tested on 47 samples collected from both a bisexual population and a unisexual population. All 13 loci were polymorphic in the bisexual population, whereas no loci were polymorphic in the unisexual population. The loss of variation in the unisexual population implies automixis with terminal fusion or gamete duplication as the mode of parthenogenesis. The markers developed in this study will be helpful for further comprehensive analysis of the genetic diversity and gene flow between bisexual and parthenogenetic lineages of P. elongatus.
... There are no high-rank taxonomic groups of terrestrial arthropods where extensive screening has failed to identify any infected species. [One possible exception to that rule is the order Phasmatodea (stick insects), where 247 individuals from 29 species have been screened for Wolbachia without a single positive specimen (Werren & Windsor, 2000;Weeks, Velten, & Stouthamer, 2003;Perez Ruiz et al., 2015).] A possible interpretation of this pattern is that no single general resistance mechanism ever evolved. ...
Wolbachia is one of the most abundant endosymbionts on earth, with a wide distribution especially in arthropods. Effective maternal transmission and the induction of various phenotypes in their hosts are two key features of this bacterium. Here, we review our current understanding of another central aspect of Wolbachia's success: their ability to switch from one host species to another. We build on the proposal that Wolbachia host shifts occur in four main steps: (i) physical transfer to a new species; (ii) proliferation within that host; (iii) successful maternal transmission; and (iv) spread within the host species. Host shift can fail at each of these steps, and the likelihood of ultimate success is influenced by many factors. Some stem from traits of Wolbachia (different strains have different abilities for host switching), others on host features such as genetic resemblance (e.g. host shifting is likely to be easier between closely related species), ecological connections (the donor and recipient host need to interact), or the resident microbiota. Host shifts have enabled Wolbachia to reach its enormous current incidence and global distribution among arthropods in an epidemiological process shaped by loss and acquisition events across host species. The ability of Wolbachia to transfer between species also forms the basis of ongoing endeavours to control pests and disease vectors, following artificial introduction into uninfected hosts such as mosquitoes. Throughout, we emphasise the many knowledge gaps in our understanding of Wolbachia host shifts, and question the effectiveness of current methodology to detect these events. We conclude by discussing an apparent paradox: how can Wolbachia maintain its ability to undergo host shifts given that its biology seems dominated by vertical transmission?
... The use of mitochondrial DNA barcodes in taxonomy has been criticized, and there are several situations in which barcode variation or lack thereof can be misleading, including heteroplasmy, introgression between species, introgression of mitochondrial genes into the nuclear genome (numts), and infection by Wolbachia or other intracellular bacterial parasites (Hurst & Jiggins, 2008;Kodandaramaiah et al., 2013;Rubinoff et al., 2006;Song et al., 2008). However, these criticisms are not particularly relevant here because it is unlikely that all five Microphyllium haskelli and the single M. pusillulum samples have numts, since all sequences could be translated into amino acids without stop codons, and because Wolbachia is unknown within Phasmida (Pérez-Ruiz et al., 2015;Sven Bradler, pers. comm. ...
Examination of unidentified Phylliidae specimens revealed a number of undescribed species from the island of Luzon, Philippines. Morphological and molecular study of specimens from the obscure phasmid genus Microphyllium Zompro, 2001, revealed a new species, which we describe as Microphyllium haskelli Cumming sp. nov.. It is here described and differentiated from the two other species in the genus, both currently only known from adults of a single sex. Pseudomi-crophyllium Cumming gen. nov. is described as a new genus within Phylliidae with the type species Pseudomicrophyllium faulkneri Cumming gen. et sp. nov. as the sole known species in the genus. As is unfortunately often the case in the leaf-mimicking family Phylliidae, this new genus and species is only known from a single specimen. In addition to the new genus, two new Phyllium (Phyllium) species from the siccifolium species-group are named and described as Ph. (Ph.) an-tonkozlovi Cumming sp. nov. and Ph. (Ph.) bourquei Cumming & Le Tirant sp. nov.. In addition to the newly described species, Phyllium (Phyllium) geryon Gray, 1843 is redescribed from a nearly perfect specimen, completing some of the morphological knowledge gaps currently missing because of the severely damaged holotype specimen. A key to all known species of Phylliidae from Luzon is included. Holotype specimens for all four new species will be deposited in the National Museum of the Philippines type collection and paratype specimens will be deposited into the San Diego Natural History Museum collection or retained within the first author's collection.
... For the giant stick insects there were few bacterial species shared between our study and previous findings [22,23]. Diamondback moth and Beet Armyworm microbiomes shared little similarity between our study and previous metagenomic surveys [24,25]. ...
... In the crop there was one bacterial and one fungal species: Serratia marcescens and Cryptococcus ramirezgomezianus, the midgut was colonised exclusively by Enterobacter cloacea, and the hindgut was the most species-rich with three bacterial strains: En. cloacea, Erwinia persicina, Se. marcescens. Another study identified Se. marcescens and Spiroplasma species in D. gigantea guts via targeted cultureindependent methods [23]. The authors did not speculate about the role of Se. marcescens, but Spiroplasma species are a common commensal endosymbiont, maternally transmitted, and in some insects responsible for impaired reproduction by inducing the selective elimination of male progeny. ...
Background
Although plants produce many secondary metabolites, currently none of these are commercial antibiotics. Insects feeding on specific plants can harbour bacterial strains resistant to known antibiotics suggesting that compounds in the plant have stimulated resistance development. We sought to determine whether the occurrence of antibiotic-resistant bacteria in insect guts was a widespread phenomenon, and whether this could be used as a part of a strategy to identify antibacterial compounds from plants. ResultsSix insect/plant pairs were selected and the insect gut bacteria were identified and assessed for antibiotic susceptibilities compared with type strains from culture collections. We found that the gut strains could be more or less susceptible to antibiotics than the type strains, or show no differences. Evidence of antibacterial activity was found in the plant extracts from five of the six plants, and, in one case Catharanthus roseus (Madagascar Periwinkle), compounds with antibacterial activity were identified. Conclusion
Bacterial strains isolated from insect guts show a range of susceptibilities to antibiotics suggesting a complex interplay between species in the insect gut microbiome. Extracts from selected plants can show antibacterial activity but it is not easy to isolate and identify the active components. We found that vindoline, present in Madagascar Periwinkle extracts, possessed moderate antibacterial activity. We suggest that plant-derived antibiotics are a realistic possibility given the advances in genomic and metabolomic methodologies.
... There is very little information about parasites and diseases in phasmids. But as for most animals there are reports of infectious diseases (Perez-Ruiz et al., 2015;Rapp, 1995) and nematodes (Yeates and Buckley, 2009) and dipteran (Pawlowski and Kraemer, 2008) parasites. Whether these infections and parasites are generalists able to infect other insects or species/phasmid-specific is not known. ...
Scientific Opinion on the Panel on Alien Organisms and Trade in Endangered species of the Norwegian Scientific Committee for Food Safety, ISBN: 978-82-8259-226-0, Oslo, Norway
... In arthropods, bacterial endosymbiotic infection (most commonly by Wolbachia) may be responsible for parthenogenetic reproduction (resulting in gamete duplication, Stouthamer et al., 1999). However, we did not screen for Wolbachia infection in this study, as this bacteria is unlikely to be responsible for parthenogenesis in the Phasmatodea order and has never been associated with parthenogenesis in facultatively parthenogenetic species (Perez-Ruiz et al., 2015). ...
... The lower rate of transition to homozygosity in locus ET6 suggests that this locus might be located further away from the centromere and therefore have higher recombination rates (given that the mechanism is automixis with terminal fusion). Although endosymbiotic infection is unlikely to be responsible for the occurrence of parthenogenetic reproduction in Phasmatodea (Perez-Ruiz et al., 2015), we are unable to completely rule out this possibility. Nonetheless, our data indicate that parthenogenesis leads to severe loss of microsatellite heterozygosity in E. tiaratum. ...
Parthenogenetic reproduction is taxonomically widespread and occurs through various cytological mechanisms, which have different impact on the genetic variation of the offspring. Extatosoma tiaratum is a facultatively parthenogenetic Australian insect (Phasmatodea), in which females oviposit continuously throughout their adult lifespan irrespective of mating. Fertilized eggs produce sons and daughters through sexual reproduction and unfertilized eggs produce female offspring via parthenogenesis. Here, we developed novel microsatellite markers for E. tiaratum and characterised them by genotyping individuals from a natural population. We then used the microsatellite markers to infer the cytological mechanism of parthenogenesis in this species. We found evidence suggesting parthenogenesis in E. tiaratum occurs through automixis with terminal fusion, resulting in substantial loss of microsatellite heterozygosity in the offspring. Loss of microsatellite heterozygosity may be associated with loss of heterozygosity in fitness related loci. The mechanism of parthenogenetic reproduction can therefore affect fitness outcomes and needs to be considered when comparing costs and benefits of sex versus parthenogenesis. This article is protected by copyright. All rights reserved.
For over 300 million years, insects have relied on symbiotic microbes for nutrition and defence. However, it is unclear whether specific ecological conditions have repeatedly favoured the evolution of symbioses, and how this has influenced insect diversification. Here, using data on 1,850 microbe–insect symbioses across 402 insect families, we found that symbionts have allowed insects to specialize on a range of nutrient-imbalanced diets, including phloem, blood and wood. Across diets, the only limiting nutrient consistently associated with the evolution of obligate symbiosis was B vitamins. The shift to new diets, facilitated by symbionts, had mixed consequences for insect diversification. In some cases, such as herbivory, it resulted in spectacular species proliferation. In other niches, such as strict blood feeding, diversification has been severely constrained. Symbioses therefore appear to solve widespread nutrient deficiencies for insects, but the consequences for insect diversification depend on the feeding niche that is invaded.
Research on gut microbiota of phytophagous insects has shown to be important for the physiological functions of insect hosts; however, little is known about the changes in gut microbiota when they are suffering from environmental stress or pathogen infections. During rearing of Phasmotaenia lanyuhensis (Phasmatodea: Phasmatidae), sluggish locomotion was usually followed by the death of the insect with a symptom of melanization in the front part of the abdomen. Therefore, the abnormal individuals were initially classified into moribund, light- and serious-symptom based on the level of abnormal physiological circumstances and melanization. The gut microbiota of these samples were further investigated by 16S metagenomic sequencing and the differences in bacterial abundance and structure of bacterial community were analyzed. A decrease in microbiota diversity was observed in the diseased P. lanyuhensis, with the abundance of phyla Proteobacteria and Firmicute relatively higher compared to those without symptom. Interestingly, principal component analysis based on the bacterial richness was correlated to the level of melanization symptom in the diseased P. lanyuhensis, suggested the change in bacterial microbiota involved in this abnormal circumstance. However, the factor that caused the initial alternation of microbiota remains to be identified. Additionally, the lack of bacterial diversity (i.e., absence of Meiothermus and Nubsella spp.) in P. lanyuhensis might reduce the fitness for surviving. This report provided the comprehensive microbiota analysis for P. lanyuhensis and concluded that either the relative abundance or the bacterial diversity of microbiota in the insect digestive system may influence the physiological functions of phytophagous insects.
The bacterium Spiroplasma ixodetis is a maternally inherited endosymbiont primarily described from ticks but also found widespread across other arthropods. While it has been identified as a male-killing agent in some insect species, the consequences of
infection with S. ixodetis in ticks are entirely unknown, and it is unclear how this endosymbiont spreads across tick species. Here, we have investigated this aspect through the examination of the diversity and evolutionary history of S. ixodetis infections in 12 tick species and 12 other arthropod species. Using a multi-locus typing approach, we identified that ticks harbour a substantial diversity of divergent S. ixodetis strains. Phylogenetic investigations revealed that these S. ixodetis strains do not cluster within a tick-specific subclade but rather exhibit distinct evolutionary origins. In their past, these strains have undergone repeated horizontal transfers between ticks and other
arthropods, including aphids and flies. This diversity pattern strongly suggests that maternal inheritance and horizontal transfers are key drivers of S. ixodetis spread, dictating global incidence of infections across tick communities. We do not, however, detect evidence of S. ixodetis-based male-killing since we observed that infections were
widely present in both males and females across populations of the African blue tick Rhipicephalus decoloratus. (More at https://doi.org/10.1016/j.ttbdis.2019.02.001)
Wolbachia is a member of the Anaplasmataceae that cannot infect vertebrates but is very widely distributed in arthropods, including many disease vectors. In addition, the presence of Wolbachia in filarial nematodes can lead to immunopathology in the mammalian host. Wolbachia displays a remarkable diversity of phenotypes, including obligate mutualism in filarial nematodes and pathogen protection in some arthropod systems. Natural or artificial Wolbachia–host relationships are currently being exploited for the control of dengue and certain filarial infections. In the near future, Wolbachia-centric methods may also be used to target other diseases, including Zika fever.
