Incidence and Diversity of Torix Rickettsia–Odonata Symbioses

Abstract

Heritable microbes are an important component of invertebrate biology, acting both as beneficial symbionts and reproductive parasites. Whilst most previous research has focussed on the ‘ Wolbachia pandemic’, recent work has emphasised the importance of other microbial symbionts. In this study, we present a survey of odonates (dragonflies and damselflies) for torix group Rickettsia , following previous research indicating that this clade can be common in other aquatic insect groups. PCR assays were used to screen a broad range of odonates from two continents and revealed 8 of 76 species tested were infected with Rickettsia . We then conducted further deeper screening of UK representatives of the Coenagrionidae damselfly family, revealing 6 of 8 UK coenagrionid species to be positive for torix Rickettsia . Analysis of Rickettsia gene sequences supported multiple establishments of symbiosis in the group. Some strains were shared between UK coenagrionid species that shared mtDNA barcodes, indicating a likely route for mitochondrial introgression between sister species. There was also evidence of coinfecting Rickettsia strains in two species. FISH analysis indicated Rickettsia were observed in the ovarioles, consistent with heritable symbiosis. We conclude that torix Rickettsia represent an important associate of odonates, being found in a broad range of species from both Europe and South America. There is evidence that coinfection can occur, vertical transmission is likely, and that symbiont movement following hybridisation may underpin the lack of ‘barcoding gap’ between well-established species pairs in the genus. Future work should establish the biological significance of the symbioses observed. Electronic supplementary material The online version of this article (10.1007/s00248-020-01568-9) contains supplementary material, which is available to authorized users.

Transmission, Tropism, and Biological Impacts of Torix Rickettsia in the Common Bed Bug Cimex lectularius (Hemiptera: Cimicidae)

“…The Rickettsia was a sister group to all other Rickettsia described previously, and the clade were named "torix Rickettsia" (Kikuchi et al, 2002). Torix Rickettsia have since been found across multiple arthropod taxa and seem to be widespread and especially common in species associated with freshwater [e.g., Culicoides midges (Pilgrim et al, 2017), dytiscid water beetles (Küchler et al, 2009), Odonata (Thongprem et al, 2020a), and Amphipoda (Park and Poulin, 2020)], but have also been detected in some terrestrial arthropods, e.g., Araneidae (Goodacre et al, 2006), Siphonaptera (Song et al, 2018), and Hemiptera (Wang et al, 2020). Whilst we now understand symbioses between invertebrates and torix Rickettsia are common, much less is known of their biological significance.…”

Widespread Torix Rickettsia in New Zealand amphipods and the use of blocking primers to rescue host COI sequences

“…Our current study provides an example, as we confirm the presence of Torix Rickettsia after discovering contaminated sequences from a previous study 31 . Similarly, the COI sequence obtained from a damselfly suggested the presence of Rickettsia in this host group (order Odonata); this has recently been confirmed by a study with a targeted screening 64 . Targeted studies are likely to uncover a huge but under-detected diversity of Torix Rickettsia, and with more data, we will be able to answer questions regarding transmission, host switching, and the evolution of pathogenicity.…”

Coverage and quality of DNA barcode references for Central and Northern European Odonata

“…This is also true for the species that share BINs. Recently, progress has been made in screening odonates for endosymbionts such as Wolbachia or Rickettsia, for example in Coenagrion from the UK (Thongprem et al, 2020), or from systems outside of our study area (Lorenzo-Carballa et al, 2019-Fiji archipelago;Salunkhe et al, 2015-Central India), documenting that these endosymbionts could constitute another route for mitochondrial introgression between species.…”