Male-biased sex-ratio distortion caused by Octosporea bayeri, a vertically and horizontally-transmitted parasite of Daphnia magna

Roth, Olivia; Ebert, Dieter; Vizoso, Dita B.; Bieger, Annette; Lass, Sandra

doi:10.1016/j.ijpara.2007.11.009

Cited by 24 publications

(27 citation statements)

References 51 publications

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“…This high spore dose was used, as it resulted in 100% infection rates of susceptible genotypes, thus reducing the chance of failed infection in susceptible hosts due to stochastic effects. We knew from previous studies that variation in resistance manifests itself most clearly in the presence/absence patterns for P. ramosa (Carius et al, 2001) and in spore counts for H. tvaerminnensis (Ebert, 2008;Roth et al, 2008). At the age of 40 days, Pasteuria exposed animals were killed to check for infection and H.tvaerminensis exposed animals (and controls) were homogenized to quantify the number of spores in their body using a cell counting chamber.…”

Section: Infection Trial Designmentioning

confidence: 99%

Genetic architecture of resistance in Daphnia hosts against two species of host-specific parasites

Routtu

Ebert

2014

Heredity

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Understanding the genetic architecture of host resistance is key for understanding the evolution of host-parasite interactions. Evolutionary models often assume simple genetics based on few loci and strong epistasis. It is unknown, however, whether these assumptions apply to natural populations. Using a quantitative trait loci (QTL) approach, we explore the genetic architecture of resistance in the crustacean Daphnia magna to two of its natural parasites: the horizontally transmitted bacterium Pasteuria ramosa and the horizontally and vertically transmitted microsporidium Hamiltosporidium tvaerminnensis. These two systems have become models for studies on the evolution of host-parasite interactions. In the QTL panel used here, Daphnia's resistance to P. ramosa is controlled by a single major QTL (which explains 50% of the observed variation). Resistance to H. tvaerminnensis horizontal infections shows a signature of a quantitative trait based in multiple loci with weak epistatic interactions (together explaining 38% variation). Resistance to H. tvaerminnensis vertical infections, however, shows only one QTL (explaining 13.5% variance) that colocalizes with one of the QTLs for horizontal infections. QTLs for resistance to Pasteuria and Hamiltosporidium do not colocalize. We conclude that the genetics of resistance in D. magna are drastically different for these two parasites. Furthermore, we infer that based on these and earlier results, the mechanisms of coevolution differ strongly for the two host-parasite systems. Only the Pasteuria-Daphnia system is expected to follow the negative frequency-dependent selection (Red Queen) model. How coevolution works in the Hamiltosporidium-Daphnia system remains unclear.

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Section: Infection Trial Designmentioning

confidence: 99%

Genetic architecture of resistance in Daphnia hosts against two species of host-specific parasites

Routtu

Ebert

2014

Heredity

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“…However, this is not the only reason for reduced carrying capacity in infected populations. Daughter production and the survival of infected mothers also declines with age Roth et al 2008). Sex-specific effects of O. bayeri on D. magna go far beyond the assumptions of Lively's model (2006).…”

Section: Discussionmentioning

confidence: 98%

“…Laboratory experiments from the O. bayeri system suggest that the production of male offspring is a direct consequence of parasite infections (Roth et al 2008). Thus, the occurrence of male offspring may have influenced the host population dynamics in the longer-running second experiment.…”

Section: Discussionmentioning

confidence: 99%

“…Further analysis revealed that this effect was somewhat dependent on the sex of the offspring. D. magna infected with O. bayeri are known to produce more male offspring than uninfected mothers (Roth et al 2008). In addition, no significant density dependence was revealed when we included males in the prevalence and competitive-ability estimates [GLM with quasi-binomial distribution and a logit link function; initial density (log 10 transformed): t = -1.49, P = 0.14; n = 48; Fig.…”

Section: Prevalencementioning

confidence: 99%

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Expression of parasite virulence at different host population densities under natural conditions

Bieger

Ebert

2009

Oecologia

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It has recently been suggested that the expression of parasite virulence depends on host population density, such that infected hosts have a higher sensitivity to density, and thus reach their carrying capacity earlier than uninfected hosts. In this scenario, parasite-induced reduction in fitness (i.e., virulence) increases with host density. We tested this hypothesis experimentally, using outdoor mesocosm populations of Daphnia magna infected by the microsporidian Octosporea bayeri. Contrary to the prediction, virulence was independent of host density. In a competition experiment with initial prevalence of 50%, O. bayeri reduced the competitive ability of infected Daphnia within the asexual growth phase independent of initial host population density. In an additional experiment we set up populations with 100% and 0% prevalence and followed their population dynamics over the whole season. Consistent with the competition experiment, we found no difference in population dynamics within the asexual growth phase of the host, suggesting that infected hosts are not more sensitive to density than uninfected hosts. The additional experiment, however, included more than the initial growth phase as did the competition experiment. Eventually, after 100 days, 100% infected populations assumed a reduced carrying capacity compared to uninfected populations. We identify and discuss three reasons for the discrepancy between our experiment and the predictions.

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“…Notorious cases of microsporidiosis in arthropods include the pepper-disease affecting the silkworm Bombyx mori and provoked by the microsporidium Nosema bombycis (37,58) and the recent global decline in honey bees that has been associated with the presence of the microsporidium Nosema ceranae (33). Microsporidia can also distort the sex ratio of arthropod populations by feminizing males, a mechanism that dramatically enhances the vertical transmission of these parasites (50,73). In fish and shellfish, microsporidiosis results in large and spherical cysts (xenomas) that typically locate on the skin or muscle tissue.…”

Section: Introductionmentioning

confidence: 99%

Microsporidia: Eukaryotic Intracellular Parasites Shaped by Gene Loss and Horizontal Gene Transfers

Corradi

2015

Annu. Rev. Microbiol.

119

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Microsporidia are eukaryotic parasites of many animals that appear to have adapted to an obligate intracellular lifestyle by modifying the morphology and content of their cells. Living inside other cells, they have lost many, or all, metabolic functions, resulting in genomes that are always gene poor and often very small. The minute content of microsporidian genomes led many to assume that these parasites are biochemically static and uninteresting. However, recent studies have demonstrated that these organisms can be surprisingly complex and dynamic. In this review I detail the most significant recent advances in microsporidian genomics and discuss how these have affected our understanding of many biological aspects of these peculiar eukaryotic intracellular pathogens.

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Male-biased sex-ratio distortion caused by Octosporea bayeri, a vertically and horizontally-transmitted parasite of Daphnia magna

Cited by 24 publications

References 51 publications

Genetic architecture of resistance in Daphnia hosts against two species of host-specific parasites

Genetic architecture of resistance in Daphnia hosts against two species of host-specific parasites

Expression of parasite virulence at different host population densities under natural conditions

Microsporidia: Eukaryotic Intracellular Parasites Shaped by Gene Loss and Horizontal Gene Transfers

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