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Studies on the pathogenicity of spiroplasmas for Drosophila pseudoobscura
Abstract:
Representatives of several currently available spiroplasma serovars were used in feeding and injection experiments involving Drosophila pseudoobscura adult flies in order to evaluate the host-range of the spiroplasmas and to determine their pathogenicity for flies. Many of the isolates injected into flies either do not survive or grow poorly, and have no negative effects on longevity or fecundity. Two spiroplasma strains, honey-bee (serovar I-2) and cornstunt (serovar I-3), can grow to high titres in injected flies but are not pathogenic. In addition to the special pathology of male lethality caused by the sex-ratio organisms (spiroplasmas) which occur naturally in several neotropical species of Drosophila, two spiroplasma serovars resulted in the death of injected flies. Spiroplasmas isolated from syrphid flies (serovar VIII) and from Cotinus beetles (serovar IX) induced the appearance of symptoms of pathology that eventually culminated in death. All such flies which were examined for the presence of spiroplasmas in their haemolymph showed them to be present in very high concentrations. The numbers of progeny which these flies produced were greatly reduced, but did consist of equal numbers of flies of both sexes. Spiroplasmas from their infected female parents were not vertically (transovarially) transmitted. The results of the feeding experiments were all negative: none of the spiroplasmas persisted in the gut or appeared in the haemolymph. None of the flies which had been fed the spiroplasma suspension displayed any pathology.
Insights
Certain Spiroplasma serovars, particularly those from syrphid flies and beetles, can infect and kill Drosophila flies. However, Spiroplasma transmission through feeding or vertically from parent flies was not observed in these experiments.
Area of Science:
- Microbiology
- Entomology
- Pathogen Host Interactions
Background:
- Spiroplasma are insect-associated bacteria with diverse host ranges and pathogenicities.
- The sex-ratio Spiroplasma are known to cause male lethality in some Drosophila species.
Purpose of the Study:
- To evaluate the host range and pathogenicity of various Spiroplasma serovars in Drosophila pseudoobscura.
- To investigate Spiroplasma survival, growth, and effects on fly longevity and reproduction after injection or feeding.
Main Methods:
- Adult Drosophila pseudoobscura flies were subjected to feeding and injection experiments with different Spiroplasma serovars.
- Fly survival, longevity, fecundity, and Spiroplasma presence in hemolymph were monitored.
- Vertical transmission was assessed by examining offspring of infected female flies.
Main Results:
- Most injected Spiroplasma isolates did not survive or cause pathology.
- Honey-bee (serovar I-2) and cornstunt (serovar I-3) Spiroplasma grew to high titers but were non-pathogenic.
- Spiroplasma from syrphid flies (serovar VIII) and Cotinus beetles (serovar IX) were pathogenic, causing mortality and reduced fecundity in flies.
- No Spiroplasma persisted in the gut or hemolymph after feeding experiments.
- Vertical transmission of Spiroplasma was not observed.
Conclusions:
- Spiroplasma serovars VIII and IX exhibit pathogenicity towards Drosophila pseudoobscura.
- Drosophila pseudoobscura is a suitable host for studying Spiroplasma pathogenicity, with injection being an effective delivery method.
- Feeding and vertical transmission routes are not significant for these Spiroplasma-Drosophila interactions.