title: Variation and covariation in infectivity, virulence and immunodepression in the host-parasite association Gammarus pulex-Pomphorhynchus laevis.
abstract: Parasites often manipulate host immunity for their own benefit, either by exacerbating or suppressing the immune response and this may directly affect the expression of parasite virulence. However, genetic variation in immunodepression, which is a prerequisite to its evolution, and the relationship between immunodepression and virulence, have rarely been studied. Here, we investigated the variation among sibships of the acanthocephalan parasite, Pomphorhynchus laevis, in infecting and in immunodepressing its amphipod host, Gammarus pulex. We also assessed the covariation between infectivity, parasite-induced immune depression and host mortality (parasite virulence). We found that infectivity, the intensity of immunodepression and virulence were variable among parasite sibships. Infectivity and the level of immunodepression were not correlated across parasite sibships. Whereas infectivity was unrelated to host mortality, we found that gammarids that were exposed to the parasite sibships that immunodepressed their hosts the most survived better. This positive covariation between host survival and immunodepression suggests that gammarids exposed to the less immunodepressive parasites could suffer from damage imposed by a higher activity of the phenoloxidase.
authors.affiliation: Université de Bourgogne, UMR CNRS 5561 Biogéosciences, Equipe Ecologie Evolutive, 6 Bd Gabriel, 21000 Dijon, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Cornet
authors.forename: Nathalie
authors.initials: N
authors.lastname: Franceschi
authors.forename: Loïc
authors.initials: L
authors.lastname: Bollache
authors.forename: Thierry
authors.initials: T
authors.lastname: Rigaud
authors.forename: Gabriele
authors.initials: G
authors.lastname: Sorci
mesh_terms: D000049:Acanthocephala / Q000276:immunology / Q000472:pathogenicity*; D033304:Amphipoda / Q000276:immunology* / Q000469:parasitology*; D000818:Animals; D005602:France; D006790:Host-Parasite Interactions; D007108:Immune Tolerance / Q000276:immunology*; D014442:Monophenol Monooxygenase / Q000276:immunology; D045483:Rivers; D016019:Survival Analysis; D014774:Virulence
chemical_list: D014442:Monophenol Monooxygenase