No fitness costs are induced by Spiroplasma infections of Aphis citricidus reared on two different host plants.

A S Guidolin,F L Cônsoli

doi:10.1590/1519-6984.201210

Abstract

Aphids can harbor several secondary symbionts that alter important aphid-related ecological traits, such as defense against natural enemies, heat tolerance and host plant utilization. One of these secondary symbionts, Spiroplasma, is well known in Drosophila as a sex modulator and by interacting with the host immune system. However, little is known on the effects of Spiroplasma on aphids, such as its influence on the host immune defense against fungi and on host plant utilization. Aphid infections by Spiroplasma are known to be low and few aphid species were reported to be infected with this secondary symbiont, however aphids belonging to the genus Aphis in neotropical regions show high infection rates by Spiroplasma. Thus, we investigated the association of Spiroplasma with the tropical aphid Aphis citricidus through comparative biology experiments on two host plants with different nutritional value to the aphid. We demonstrate Spiroplasma induced no significant fitness costs to A. citricidus on either host plant as no changes in the fitness traits we assessed were observed. Spiroplasma infection only induced sutle changes on host longevity and fecundity. Therefore, we concluded Spiroplasma established a neutral interaction with A. citricidus under the selection pressure we tested, and argue on stress conditions that could better demonstrate the role of Spiroplasma in A. citricidus bioecology and associated costs involved.

Highlights

Aphids are associated with many bacterial symbionts, with the obligate symbiont Buchnera aphidicola supplementing the host diet with essential amino acids and vitamins (Buchner, 1965; Douglas, 1998; Hansen and Moran, 2014), Braz
For example H. defensa, S. symbiotica and R. viridis are linked to resistance to macroorganisms (Oliver et al, 2010; Tsuchida et al, 2014), while R. insecticola, R. viridis, Rickettsia, Spiroplasma and X-type are associated with protection against microorganisms (Ferrari et al, 2001; Łukasik et al, 2013b; Tsuchida et al, 2014; Heyworth and Ferrari, 2015)
Wolbachia is known to confer protection against viruses in Drosophila and mosquito, but the role of this bacterium in aphids remains to be explored (Teixeira et al, 2008; Augustinos et al, 2011; Moreira et al, 2009). Besides their defensive role in associated aphids, R. insecticola, S. symbiotica and X-type were linked with tolerance to heat stress (Montllor et al, 2002; Russell and Moran, 2006; Heyworth and Ferrari, 2015), Spiroplasma, Arsenophonus and Wolbachia with reproductive alterations (Bourtzis and Miller, 2006), and R. insecticola and Arsenophonus with host plant use (Leonardo and Muiru, 2003; Ferrari et al, 2007)

Summary

Introduction

Aphids are associated with many bacterial symbionts, with the obligate symbiont Buchnera aphidicola supplementing the host diet with essential amino acids and vitamins (Buchner, 1965; Douglas, 1998; Hansen and Moran, 2014), Braz. Wolbachia is known to confer protection against viruses in Drosophila and mosquito, but the role of this bacterium in aphids remains to be explored (Teixeira et al, 2008; Augustinos et al, 2011; Moreira et al, 2009) Besides their defensive role in associated aphids, R. insecticola, S. symbiotica and X-type were linked with tolerance to heat stress (Montllor et al, 2002; Russell and Moran, 2006; Heyworth and Ferrari, 2015), Spiroplasma, Arsenophonus and Wolbachia with reproductive alterations (Bourtzis and Miller, 2006), and R. insecticola and Arsenophonus with host plant use (Leonardo and Muiru, 2003; Ferrari et al, 2007)

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Results

Conclusion