We tested the effects of circadian temperature fluctuations on a series of thermal plasticity traits in a model of adaptive seasonal plasticity, the Bicyclus anynana butterfly.
Within-host bacterial adaptations are generally focused on antibiotic resistance, rarely on the adaptation to the environment given by the host, and the potential trade-off hindering adaptations to each step of the infection are rarely considered. Using Drosophila melanogaster as host and the bacteria Xenorhabdus nematophila, we studied those trade-offs that are key to understand intra-host evolution, and thus the dynamics of the infection.
To understand the mechanisms of antagonistic coevolution, it is crucial to identify the genetics of parasite resistance. Using QTL approach, we discovered a second P. ramosa attachment site and a novel host-resistance locus, with implications for both for the coevolutionary dynamics (e.g., Red Queen and the role of recombination), and for the evolution and epidemiology of the infection process.
Distinct life stages can represent drastically different environments for parasites especially when larval and adult life stages are bridged by a complete metamorphosis. We showed that systemic infection with an extracellular bacterium can transverse life stages.
Our work has elucidated the mechanism of the difference between males and females Drosophila melanogaster in terms of susceptibility to infection. Altogether, our data demonstrate that Toll pathway activity differs between male and female D. melanogaster in response to bacterial infection, thus identifying innate immune signalling as a determinant of sexual immune dimorphism.
A central problem with biomedicine is to understand why two individuals exposed to seemingly identical infections may have radically different clinical outcomes. Using the Drosophila melanogaster model, we analyse in depth, both through functional genetics and mathematical modelling, the main determinants that underlie the stochastic outcome of infection.
By focusing this review on the biology of the bacterial parasite Pasteuria ramosa and its aquatic crustacean host Daphnia, we demonstrate that a population biology approach taking into consideration the natural genetic and environmental variation at each step of the infection can greatly aid our understanding of the evolutionary processes shaping disease traits.
Seminal fluid proteins coagulate inside the female Drosophila into a structure known as the mating plug. We found PEBme knockdown in males compromised mating plug coagulation in their mates and I showed with macrophotography that the inability of females to subsequently retain the ejaculate in their reproductive tracts after mating was frequent. Our set of results highlight the importance of the posterior mating plug in reproduction.
Successful infection depends on the outcome of multiple steps and only some steps of the infection process may be critical in determining a parasites host range. We found that while parasite attachment was possible across several host species (suggesting that alleles on the locus controlling attachment are shared among different host species that diverged 100 million years), proliferation occurred only in the native host species. Host range was therefore limited by one step of the infection.
For host-parasite coevolution to lead to an ongoing advantage for rare genotypes, parasites should infect specific host genotypes and hosts should resist specific parasite genotypes. Using the crustacean Daphnia magna and its parasitic bacterium Pasteuria ramosa, we described for the first time the genetics model capturing best such specificity, the matching-allele models (MAMs). I performed all the attachment tests of this study.
Because they reproduce parthenogenetically, Daphnia are predominantly female. The parasites in these populations therefore necessarily evolve more often in females than male hosts. We have shown here that a parasite can be better adapted to the sex it encounters most frequently, empirically supporting the hypothesis proposed Duneau & Ebert PLoS Biology 2012.
The penetration of parasites into the host is a key step for a successful infection and the epithelium is the first line of host defence. We used the crustacean Daphnia magna to show that moulting influences the likelihood of infection by the bacterium Pasteuria ramosa. Hence, moulting is not only a weakness but can be beneficial to prevent infection by shedding bacteria.
In this “essay” we propose for the first time the idea that the sexual dimorphism of diseases may be the result of the specific adaptation of parasites to the sex of their host. Similarly, as organisms adapt to the environment to which they are most frequently exposed, parasites can adapt to the sex they encounter most frequently (e.g., either because males and females are exposed differently, or because one sex is more easily infected than another due to immune differences). As a result, parasites behave differently depending on the sex they infect.
We use a classical genetics approach to examine the mode of inheritance of infection outcome in the crustacean Daphnia magna when exposed to the bacterial parasite Pasteuria ramosa. We find host genotypes were either completely resistance or completely susceptibility to given parasite genotypes, that resistance is dominant, and inherited in a pattern consistent with Mendelian segregation of a single-locus with two alleles.
Investigate the mechanism of infection underlying coevolution between a host (Daphnia magna) and his parasite (Pasteuria ramosa). We found that the specificity depends on the capacity of the parasite to attach or not to the host oesophagus. We published here the “attachment test” method which is used to quickly determine the ability of the bacteria of a given genotype to infect a given host genotype.
We studied the mechanisms hairworms use to increase the encounter rate between their host and water. We showed that hairworm infection modifies cricket behavior by inducing directed responses to light, a condition from which they mostly recover once the parasite is released. This parasite adaptation may be the best way to find a body of water in a forest.
We combine site-occupancy modeling and molecular assays to evaluate patterns of infection in the marine cycle of Lyme borreliosis. Our results show that bacterial detection varies strongly among tick races leading to vector-specific biases if raw counts are used to calculate Borrelia prevalence. Overall prevalence is higher than suspected and certain vector–host combinations likely contribute more than others to the local dynamics and large-scale dispersal of Borrelia spirochetes.
Many trophically transmitted parasites alters the behaviour of their intermediate host to favour transmission to definitive hosts. Shrimp juveniles remain inside the female marsupial brood pouch and are subject to the same risk of predation as their mothers. We explored the idea that juveniles from parasitized females would accelerate their development, or exit the marsupium at an earlier stage, to avoid predation by birds. But juveniles from parasitized females exited the marsupial brood pouch significantly later.
We studied the diversity of Borrelia spp. circulating in seabirds. Our findings indicate that Lyme disease spirochetes circulating in the marine system are more diverse than previously described and support the hypothesis that seabirds may be an important component in the global epidemiology and evolution of Lyme disease.
Following the ingestion of the insect host by fish or frogs, the parasitic hairworm is able to actively exit both its host and the gut of the predator. Using proteomics tools, we described the physiological basis of this anti-predator response. We also showed that the escaped response does not have a fitness cost.
As prisoners in their living habitat, parasites should be vulnerable to destruction by the predators of their hosts. We show that the parasitic hairworm is able to escape from the predators (fish or frog) of its insect hosts.
We studied the consequence of behavioural manipulation by parasites on the ecology of host populations. We compared several biological characteristics of two discrete subpopulations, one living at the surface (infected individuals) and the other living near the bottom (uninfected individuals). Infected gammarids are not simply normal hosts with an aberrant behaviour, they are more deeply modified in ways that may substantially alter host population ecology.