Wolbachia infections of tephritid fruit flies: molecular evidence for five distinct strains in a single host species

Endosymbiotic bacteria of the genus Wolbachia are widespread among arthropods and can induce cytoplasmic incompatibility, thelytokous parthenogenesis, male-killing or feminization in their hosts. Here, we report phylogenetic relationships of Wolbachia in tephritid fruit flies based on wsp gene sequences. We also report, for the first time, five distinct strains of Wolbachia in Bactrocera ascita sp. B. Four of the five Wolbachia strains found in this species were in the same groups as those found in other tephritid fruit flies, suggesting possible horizontal transmission of Wolbachia from other fruit flies into B. ascita sp. B. The unreliability of wsp-specific group primers demonstrated in this study suggests that these primers might be useful only for preliminary identification of Wolbachia. Final determination of group affiliation needs to be verified with wsp sequence data.

Wolbachia infections of phlebotomine sand flies (Diptera: Psychodidae)

Old and New World phlebotomine sand fly species were screened for infection with Wolbachia, intracellular bacterial endosymbionts found in many arthropods and filarial nematodes. Of 53 samples representing 15 species, nine samples of four species were found positive for Wolbachia by polymerase chain reaction amplification using primers for the Wolbachia surface protein (wsp) gene. Five of the wsp gene fragments from four species were cloned, sequenced, and used for phylogenetic analysis. These wsp sequences were placed in three different clades within the arthropod associated Wolbachia (groups A and B), suggesting that Wolbachia has infected sand flies on more than one occasion. Two distantly related sand fly species, Lutzomyia (Psanthyromyia) shannoni (Dyar) and Lutzomyia (Nyssomyia) whitmani (Antunes & Coutinho), infected with an identical Wolbachia strain suggest a very recent horizontal transmission.

Field evidence for mechanical transmission of rabbit haemorrhagic disease virus (RHDV) by flies (Diptera : Calliphoridae) among wild rabbits in Australia

Field collected flies were screened for the presence of rabbit haemorrhagic disease virus (RHDV) by applying reverse transcriptase PCR (RT-PCR) in which primers specific to the capsid protein of the virus were used. The virus was detected in flies from locations where rabbit haemorrhagic disease (RHD) was reported and also soon after the release of RHDV in a 'clean' area. Oral and/or anal excretions of flies (flyspots) were found to contain viable virus and oral inoculation of rabbits revealed that a single flyspot was able to cause RHD. We conclude that flyspots are a major potential source of the virus for oral or conjunctival transmission of the virus to rabbits. (C) 1998 Elsevier Science B.V. All rights reserved.

Genes, morphology and agreement: congruence in Australian anthracine bee flies (Diptera : Bombyliidae : Anthracinae)

Almost half of the 4547 described bee flies (Bombyliidae: Diptera) in the world belong to the subfamily Anthracinae, with most of the world's diversity in three cosmopolitan tribes: Villini, Anthracini and Exoprosopini. Molecular data from 815 base pairs of 16S mitochondrial DNA and morphological characters from species-groups of these tribes in Australia were analysed cladistically. The results show that the relationships between the anthracine tribes reflect those found in a previous morphological analysis. The genera of the Anthracinae in Australia are monophyletic, except for Ligyra Newman, and are assigned to tribes. Although simultaneous analysis of the combined molecular and morphological data produced clades found in both separate analyses, the different data sources are significantly incongruent. We use phylogenetic measures to examine support for the relationships among the Australian Anthracinae inferred by the molecular and morphological data.

Australian Glow-worms in Caves

Glow-worms are the larvae of a fly from the family Keroplatidae. Their closest relatives are the “fungus flies��� that seek out mushrooms for their larvae to consume. Glow-worms have gone out on an evolutionary limb, albeit a successful one. They have lost their association with fungi and have instead become carnivorous. The unique feature of glow-worms is their ability to bioluminesce—to produce light.

Evidence for a global Wolbachia replacement in Drosophila melanogaster

Wolbachia are maternally inherited intracellular α-Proteobacteria found in numerous arthropod and filarial nematode species [1, 2 and 3]. They influence the biology of their hosts in many ways. In some cases, they act as obligate mutualists and are required for the normal development and reproduction of the host [4 and 5]. They are best known, however, for the various reproductive parasitism traits that they can generate in infected hosts. These include cytoplasmic incompatibility (CI) between individuals of different infection status, the parthenogenetic production of females, the selective killing of male embryos, and the feminization of genetic males [1 and 2]. Wolbachia infections of Drosophila melanogaster are extremely common in both wild populations and long-term laboratory stocks [6, 7 and 8]. Utilizing the newly completed genome sequence of Wolbachia pipientis wMel [9], we have identified a number of polymorphic markers that can be used to discriminate among five different Wolbachia variants within what was previously thought to be the single clonal infection of D. melanogaster. Analysis of long-term lab stocks together with wild-caught flies indicates that one of these variants has replaced the others globally within the last century. This is the first report of a global replacement of a Wolbachia strain in an insect host species. The sweep is at odds with current theory that cannot explain how Wolbachia can invade this host species given the observed cytoplasmic incompatibility characteristics of Wolbachia infections in D. melanogaster in the field [6].

A stable triple Wolbachia infection in Drosophila with nearly additive incompatibility effects

Drosophila simulans strains infected with three different Wolbachia strains were generated by experimental injection of a third symbiont into a naturally double-infected strain. This transfer led to a substantial increase in total Wolbachia density in the host strain. Each of the three symbionts was stably transmitted in the presence of the other two. Triple-infected males were incompatible with double-infected females. No evidence was obtained for interference between modification effects of the different Wolbachia strains in males. Some incompatibility was observed between triple-infected males and females. However, this incompatibility reaction is not a specific property of triple-infected flies, because it was also observed in double-infected strains.

Analysis of Wolbachia protein synthesis in Drosophila in vivo

Intracellular Wolbachia infections are extremely common in arthropods and exert profound control over the reproductive biology of the host. However, very little is known about the underlying molecular mechanisms which mediate these interactions with the host. We examined protein synthesis by Wolbachia in a Drosophila host in vivo by selective metabolic labelling of prokaryotic proteins and subsequent analysis by 1D and 2D gel electrophoresis. Using this method we could identify the major proteins synthesized by Wolbachia in ovaries and testes of flies. Of these proteins the most abundant was of low molecular weight and showed size variation between Wolbachia strains which correlated with the reproductive phenotype they generated in flies. Using the gel systems we employed it was not possible to identify any proteins of Wolbachia origin in the mature sperm cells of infected flies.

Replacement of the natural Wolbachia symbiont of Drosophila simulans with a mosquito counterpart

Inherited rickettsial symbionts of the genus Wolbachia occur commonly in arthropods and have been implicated in the expression of parthenogenesis, feminization and cytoplasmic incompatibility phenomena in their respective hosts. Here we use purified Wolbachia from the Asian tiger mosquito, Aedes albopictus, to replace the natural infection of Drosophila simulans by means of embryonic microinjection techniques. The transferred Wolbachia infection behaves like a natural Drosophila infection with regard to its inheritance, cytoskeleton interactions and ability to induce incompatibility when crossed with uninfected flies. The transinfected flies are bidirectionally incompatible with all other naturally infected strains of Drosophila simulans, however, and as such represent a unique crossing type. The successful transfer of this symbiont between distantly related hosts suggests that it may be possible to introduce this agent experimentally into arthropod species of medical and agricultural importance in order to manipulate natural populations genetically.

Parasites in Drosophila embryos

We wish to alert people studying early embryonic development in the fruit-fly Drosophila melanogaster of the possible presence of commensal parasites in some stocks.

Biogenesis of sex pheromones in the female olive fruit-fly

A likely pathway to the sex pheromones of Bactrocera oleae (olive fruit-fly) is presented, based mainly on feeding experiments with deuterium labelled precursors.