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Conditional Reduction of Predation Risk Associated with a Facultative Symbiont in an Insect.

Polin S, Le Gallic JF, Simon JC, Tsuchida T, Outreman Y - PLoS ONE (2015)

Bottom Line: As body colour affects the susceptibility towards natural enemies in aphids, the influence of the colour change due to these facultative symbionts on the host survival in presence of predators was tested.Due to results from uninfected aphids (i.e., more green ones attacked), the main assumption is that this symbiotic infection would deter the predatory ladybird feeding by reducing the profitability of their hosts rather than decreasing host detection through body colour change.The underlying mechanisms and ecological consequences of these symbiotic effects are discussed.

View Article: PubMed Central - PubMed

Affiliation: UMR 1349 IGEPP, Agrocampus Ouest, 35042, Rennes, France.

ABSTRACT
Symbionts are widespread among eukaryotes and their impacts on the ecology and evolution of their hosts are meaningful. Most insects harbour obligate and facultative symbiotic bacteria that can influence their phenotype. In the pea aphid Acyrthosiphon pisum, an astounding symbiotic-mediated phenotype has been recently observed: when infected with the symbiotic bacteria Rickettsiella viridis, young red aphid larvae become greener at adulthood and even darker green when co-infected with Rickettsiella viridis and Hamiltonella defensa. As body colour affects the susceptibility towards natural enemies in aphids, the influence of the colour change due to these facultative symbionts on the host survival in presence of predators was tested. Our results suggested that the Rickettsiella viridis infection may impact positively host survival by reducing predation risk. Due to results from uninfected aphids (i.e., more green ones attacked), the main assumption is that this symbiotic infection would deter the predatory ladybird feeding by reducing the profitability of their hosts rather than decreasing host detection through body colour change. Aphids co-infected with Rickettsiella viridis and Hamiltonella defensa were, however, more exposed to predation suggesting an ecological cost associated with multiple infections. The underlying mechanisms and ecological consequences of these symbiotic effects are discussed.

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Related in: MedlinePlus

The experimental treatments.The six experimental treatments combining pairs of aphid types in order to test the effects of colour and symbiotic complement on aphid survival under predation pressure. Aphid type was defined as a combination of aphid colour and symbiotype. The aphid survival rate was tested (A) between red and green aphid types with different symbiotic complement and (B) among green types differing by their symbiotic complements. Letters reported in the aphids stand for the symbiotic complement including the obligate symbiont Buchnera (B) and the two facultative symbionts, Rickettsiella (R) and Hamiltonella (H). The name code of each treatment is indicated on the link between considered aphid types (Capital letter: the aphid colour; Subscript letters: symbiotic complement).
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pone.0143728.g001: The experimental treatments.The six experimental treatments combining pairs of aphid types in order to test the effects of colour and symbiotic complement on aphid survival under predation pressure. Aphid type was defined as a combination of aphid colour and symbiotype. The aphid survival rate was tested (A) between red and green aphid types with different symbiotic complement and (B) among green types differing by their symbiotic complements. Letters reported in the aphids stand for the symbiotic complement including the obligate symbiont Buchnera (B) and the two facultative symbionts, Rickettsiella (R) and Hamiltonella (H). The name code of each treatment is indicated on the link between considered aphid types (Capital letter: the aphid colour; Subscript letters: symbiotic complement).

Mentions: Each experiment consisted of a potted Vicia faba plant containing thirty aphid individuals: fifteen individuals from one aphid type and fifteen individuals from another aphid type. For each replicate, the genotype used for a given aphid type was randomly chosen among the two or three available ones (see Table 1). The thirty aphid individuals were placed on the plant one hour before the experiment for their settlement. A ladybird was then introduced in the experimental system and the plant was covered with a punctured plastic bag in order to avoid insect escape and external disturbance. Twenty-four hours later, the predator was extracted from the trial and the surviving aphid individuals (i.e., not consumed by the predator) of the two aphid types were counted. When the experiment considered only green aphids with different symbiotic status, their distinction was allowed by symbiotyping the surviving individuals (diagnostic PCR). For more details on extraction, PCR procedure or electrophoresis of PCR products, see [17]. Fig 1 presents the six aphid type combinations (i.e., treatments) tested. Three treatments combined red and green adult aphids with different symbiotic complements and three other treatments combined green adult aphids with various symbiotic consortia. For each treatment, twenty replicates were done (except for treatment GBR-GBRH where the number of replicates was 16).


Conditional Reduction of Predation Risk Associated with a Facultative Symbiont in an Insect.

Polin S, Le Gallic JF, Simon JC, Tsuchida T, Outreman Y - PLoS ONE (2015)

The experimental treatments.The six experimental treatments combining pairs of aphid types in order to test the effects of colour and symbiotic complement on aphid survival under predation pressure. Aphid type was defined as a combination of aphid colour and symbiotype. The aphid survival rate was tested (A) between red and green aphid types with different symbiotic complement and (B) among green types differing by their symbiotic complements. Letters reported in the aphids stand for the symbiotic complement including the obligate symbiont Buchnera (B) and the two facultative symbionts, Rickettsiella (R) and Hamiltonella (H). The name code of each treatment is indicated on the link between considered aphid types (Capital letter: the aphid colour; Subscript letters: symbiotic complement).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664394&req=5

pone.0143728.g001: The experimental treatments.The six experimental treatments combining pairs of aphid types in order to test the effects of colour and symbiotic complement on aphid survival under predation pressure. Aphid type was defined as a combination of aphid colour and symbiotype. The aphid survival rate was tested (A) between red and green aphid types with different symbiotic complement and (B) among green types differing by their symbiotic complements. Letters reported in the aphids stand for the symbiotic complement including the obligate symbiont Buchnera (B) and the two facultative symbionts, Rickettsiella (R) and Hamiltonella (H). The name code of each treatment is indicated on the link between considered aphid types (Capital letter: the aphid colour; Subscript letters: symbiotic complement).
Mentions: Each experiment consisted of a potted Vicia faba plant containing thirty aphid individuals: fifteen individuals from one aphid type and fifteen individuals from another aphid type. For each replicate, the genotype used for a given aphid type was randomly chosen among the two or three available ones (see Table 1). The thirty aphid individuals were placed on the plant one hour before the experiment for their settlement. A ladybird was then introduced in the experimental system and the plant was covered with a punctured plastic bag in order to avoid insect escape and external disturbance. Twenty-four hours later, the predator was extracted from the trial and the surviving aphid individuals (i.e., not consumed by the predator) of the two aphid types were counted. When the experiment considered only green aphids with different symbiotic status, their distinction was allowed by symbiotyping the surviving individuals (diagnostic PCR). For more details on extraction, PCR procedure or electrophoresis of PCR products, see [17]. Fig 1 presents the six aphid type combinations (i.e., treatments) tested. Three treatments combined red and green adult aphids with different symbiotic complements and three other treatments combined green adult aphids with various symbiotic consortia. For each treatment, twenty replicates were done (except for treatment GBR-GBRH where the number of replicates was 16).

Bottom Line: As body colour affects the susceptibility towards natural enemies in aphids, the influence of the colour change due to these facultative symbionts on the host survival in presence of predators was tested.Due to results from uninfected aphids (i.e., more green ones attacked), the main assumption is that this symbiotic infection would deter the predatory ladybird feeding by reducing the profitability of their hosts rather than decreasing host detection through body colour change.The underlying mechanisms and ecological consequences of these symbiotic effects are discussed.

View Article: PubMed Central - PubMed

Affiliation: UMR 1349 IGEPP, Agrocampus Ouest, 35042, Rennes, France.

ABSTRACT
Symbionts are widespread among eukaryotes and their impacts on the ecology and evolution of their hosts are meaningful. Most insects harbour obligate and facultative symbiotic bacteria that can influence their phenotype. In the pea aphid Acyrthosiphon pisum, an astounding symbiotic-mediated phenotype has been recently observed: when infected with the symbiotic bacteria Rickettsiella viridis, young red aphid larvae become greener at adulthood and even darker green when co-infected with Rickettsiella viridis and Hamiltonella defensa. As body colour affects the susceptibility towards natural enemies in aphids, the influence of the colour change due to these facultative symbionts on the host survival in presence of predators was tested. Our results suggested that the Rickettsiella viridis infection may impact positively host survival by reducing predation risk. Due to results from uninfected aphids (i.e., more green ones attacked), the main assumption is that this symbiotic infection would deter the predatory ladybird feeding by reducing the profitability of their hosts rather than decreasing host detection through body colour change. Aphids co-infected with Rickettsiella viridis and Hamiltonella defensa were, however, more exposed to predation suggesting an ecological cost associated with multiple infections. The underlying mechanisms and ecological consequences of these symbiotic effects are discussed.

Show MeSH
Related in: MedlinePlus