Fight or Flight? Alternative Defense of the Pea Aphids, Acyrthosiphon pisum on Different Host Plants (original) (raw)
Related papers
PLoS ONE, 2013
Pea aphids have an obligate nutritional symbiosis with the bacteria Buchnera aphidicola and frequently also harbor one or more facultative symbionts. Aphids are also susceptible to bacterial pathogen infections, and it has been suggested that aphids have a limited immune response towards such pathogen infections compared to other, more well-studied insects. However, aphids do possess at least some of the genes known to be involved in bacterial immune responses in other insects, and immune-competent hemocytes. One possibility is that immune priming with microbial elicitors could stimulate immune protection against subsequent bacterial infections, as has been observed in several other insect systems. To address this hypothesis we challenged aphids with bacterial immune elicitors twenty-four hours prior to live bacterial pathogen infections and then compared their survival rates to aphids that were not pre-exposed to bacterial signals. Using two aphid genotypes, we found no evidence for immune protection conferred by immune priming during infections with either Serratia marcescens or with Escherichia coli. Immune priming was not altered by the presence of facultative, beneficial symbionts in the aphids. In the absence of inducible immune protection, aphids may allocate energy towards other defense traits, including production of offspring with wings that could escape deteriorating conditions. To test this, we monitored the ratio of winged to unwinged offspring produced by adult mothers of a single clone that had been exposed to bacterial immune elicitors, to live E. coli infections or to no challenge. We found no correlation between immune challenge and winged offspring production, suggesting that this mechanism of defense, which functions upon exposure to fungal pathogens, is not central to aphid responses to bacterial infections.
Effects of Host Plants on the Growth, Reproduction, and Defense in Pea Aphids, Acyrthosiphon Pisum
Background: Pea aphids (Acyrthosiphon pisum) possess a weak immune system, but they can firmly mount immunological responses. However, the influence of different plants on their defense against different microbes remains largely unknown. In addition, no previous research has integrated the growth, reproduction, and defense responses of pea aphids feeding on different plants. Objective: This study aims to investigate the growth, reproduction, and defense responses of pea aphids feeding on different plants. Methods: Pea aphids were cultivated on both Medicago sativa and Vicia faba. Growth and reproduction were evaluated. Additionally, we monitored the survival and microbial loads of pea aphids after bacterial and fungal infections. Results: Pea aphids reared on M. sativa had lower growth, lower intrinsic rate of increase, and lower finite rate of increase when compared to aphids feeding on V. faba. The net reproduction was lower in aphids feeding on M. sativa, although the difference was not significant. The mean time of generation and pre-reproductive periods was longer for aphids reared on M. sativa than for aphids reared on V. faba. In the infection experiments, we found that aphid survival was not affected by the host plant. However, aphids reared on M. sativa generally harbored fewer microbial loads than those reared on V. faba. Conclusions: The growth and reproduction of pea aphids are affected by the host plant. Aphids feeding on different plants had different tolerances to microbial infections. Our study sheds light on improving biological control program for aphids.
Pea aphids have an obligate nutritional symbiosis with the bacteria Buchnera aphidicola and frequently also harbor one or more facultative symbionts. Aphids are also susceptible to bacterial pathogen infections, and it has been suggested that aphids have a limited immune response towards such pathogen infections compared to other, more well-studied insects. However, aphids do possess at least some of the genes known to be involved in bacterial immune responses in other insects, and immune-competent hemocytes. One possibility is that immune priming with microbial elicitors could stimulate immune protection against subsequent bacterial infections, as has been observed in several other insect systems. To address this hypothesis we challenged aphids with bacterial immune elicitors twenty-four hours prior to live bacterial pathogen infections and then compared their survival rates to aphids that were not pre-exposed to bacterial signals. Using two aphid genotypes, we found no evidence for immune protection conferred by immune priming during infections with either Serratia marcescens or with Escherichia coli. Immune priming was not altered by the presence of facultative, beneficial symbionts in the aphids. In the absence of inducible immune protection, aphids may allocate energy towards other defense traits, including production of offspring with wings that could escape deteriorating conditions. To test this, we monitored the ratio of winged to unwinged offspring produced by adult mothers of a single clone that had been exposed to bacterial immune elicitors, to live E. coli infections or to no challenge. We found no correlation between immune challenge and winged offspring production, suggesting that this mechanism of defense, which functions upon exposure to fungal pathogens, is not central to aphid responses to bacterial infections.
Entomologia Experimentalis Et Applicata, 2010
In order to reduce parasite-induced mortality, hosts may be involved in mutualistic interactions in which the partner contributes to resistance against the parasite. The pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae), harbours secondary bacterial endosymbionts, some of which have been reported to confer resistance against aphid parasitoids. Although this resistance often results in death of the developing parasitoid larvae, some parasitoid individuals succeed in developing into adults. Whether these individuals suffer from fitness reduction compared to parasitoids developing in pea aphid clones without symbionts has not been tested so far. Using 30 pea aphid clones that differed in their endosymbiont complement, we studied the effects of these endosymbionts on aphid resistance against the parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae: Aphidiinae), host-parasitoid physiological interactions, and fitness of emerging adult parasitoids. The number of symbiont species in an aphid clone was positively correlated with a number of resistance measurements but there were also clear symbiont-specific effects on the host-parasitoid interaction. As in previous studies, pea aphid clones infected with Hamiltonella defensa Moran et al. showed resistance against the parasitoid. In addition, pea aphid clones infected with Regiella insecticola Moran et al. and co-infections of H. defensa-Spiroplasma, R. insecticola-Spiroplasma, and R. insecticola-H. defensa showed reduced levels of parasitism and mummification. Parasitoids emerging from symbiontinfected aphid clones often had a longer developmental time and reduced mass. The number of teratocytes was generally lower when parasitoids oviposited in aphid clones with a symbiont complement. Interestingly, unparasitized aphids infected with Serratia symbiotica Moran et al. and R. insecticola had a higher fecundity than unparasitized aphids of uninfected pea aphid clones. We conclude that in addition to conferring resistance, pea aphid symbionts also negatively affect parasitoids that successfully hatch from aphid mummies. Because of the link between aphid resistance and the number of teratocytes, the mechanism underlying resistance by symbiont infection may involve interference with teratocyte development.
Insects, 2021
Aphids use an alarm pheromone, E-β farnesene (EBF), to warn conspecifics of potential danger. The antennal sensitivity and behavioural escape responses to EBF can be influenced by different factors. In the pea aphid, Acyrthosiphon pisum, different biotypes are adapted to different legume species, and within each biotype, different genotypes exist, which can carry or not Hamiltonella defensa, a bacterial symbiont that can confer protection against natural enemies. We investigate here the influence of the aphid genotype and symbiotic status on the escape behaviour using a four-way olfactometer and antennal sensitivity for EBF using electroantennograms (EAGs). Whereas the investigated three genotypes from two biotypes showed significantly different escape and locomotor behaviours in the presence of certain EBF doses, the infection with H. defensa did not significantly modify the escape behaviour and only marginally influenced the locomotor behaviour at high doses of EBF. Dose-response ...
Aphid-encoded variability in susceptibility to a parasitoid
BMC Evolutionary Biology, 2014
Background: Many animals exhibit variation in resistance to specific natural enemies. Such variation may be encoded in their genomes or derived from infection with protective symbionts. The pea aphid, Acyrthosiphon pisum, for example, exhibits tremendous variation in susceptibility to a common natural enemy, the parasitic wasp Aphidius ervi. Pea aphids are often infected with the heritable bacterial symbiont, Hamiltonella defensa, which confers partial to complete resistance against this parasitoid depending on bacterial strain and associated bacteriophages. That previous studies found that pea aphids without H. defensa (or other symbionts) were generally susceptible to parasitism, together with observations of a limited encapsulation response, suggested that pea aphids largely rely on infection with H. defensa for protection against parasitoids. However, the limited number of uninfected clones previously examined, and our recent report of two symbiont-free resistant clones, led us to explicitly examine aphid-encoded variability in resistance to parasitoids. Results: After rigorous screening for known and unknown symbionts, and microsatellite genotyping to confirm clonal identity, we conducted parasitism assays using fifteen clonal pea aphid lines. We recovered significant variability in aphid-encoded resistance, with variation levels comparable to that contributed by H. defensa. Because resistance can be costly, we also measured aphid longevity and cumulative fecundity of the most and least resistant aphid lines under permissive conditions, but found no trade-offs between higher resistance and these fitness parameters. Conclusions: These results indicate that pea aphid resistance to A. ervi is more complex than previously appreciated, and that aphids employ multiple tactics to aid in their defense. While we did not detect a tradeoff, these may become apparent under stressful conditions or when resistant and susceptible aphids are in direct competition. Understanding sources and amounts of variation in resistance to natural enemies is necessary to understand the ecological and evolutionary dynamics of antagonistic interactions, such as the potential for coevolution, but also for the successful management of pest populations through biological control.
Biological Control, 2017
Endosymbiont interactions with hosts have important effects on fitness, including the fitness of many pest and beneficial species. Among these interactions, facultative endosymbiotic bacteria can protect aphids from parasitoids. Aphis craccivora and Acyrthosiphon pisum can harbor the symbiotic bacteria Hamiltonella defensa and its bacteriophage APSE. Infection by H. defensa defends these aphids against some but not all parasitoid species in the hymenopteran family Braconidae. Here, we report results on the effect of H. defensa on parasitism of these aphids by species in the other major lineage of aphid parasitoids, Aphelinus species in the family Aphelinidae. Parasitism of aphids infected with H. defensa/APSE by two Aphelinus species did not differ from that of uninfected aphids. While Aphelinus atriplicis showed no difference in fitness components between infected and uninfected aphids, Aphelinus glycinis actually produced more adult progeny and larger female progeny on infected than on uninfected aphids. Aphelinus glycinis may increase host quality for itself by changing the titer of nutritional versus protective bacteria in such a way that aphids infected with H. defensa can be made more suitable for parasitoid development than uninfected aphids. Our results and reasoning suggest that these Aphelinus species may be less prone to harm by H. defensa/APSE that affect eggs because they have anhydropic, heavily chorionated eggs, which may not absorb toxins during embryogenesis.
Differences in defensive behaviour between host-adapted races of the pea aphid
Ecological Entomology, 2010
1. Host races, i.e. host-adapted populations in partial reproductive isolation, have been reported in a growing number of insect herbivores including aphids. The pea aphid Acyrthosiphon pisum encompasses distinct races highly specialised on various Fabaceae plants. Races have been well documented at both the ecological and genetic level. However, little is known about possible behavioural differences between host races other than those involved in plant choice.