Haunted by the past: Evidence for dormant stage banks of microparasites and epibionts of Daphnia

Decaestecker, Ellen; Lefever, Christophe; Meester, Luc De; Ebert, Dieter

doi:10.4319/lo.2004.49.4_part_2.1355

Cited by 59 publications

(69 citation statements)

References 55 publications

(68 reference statements)

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“…An earlier study has further shown that O. bayeri spores survive drought (Vizoso et al 2005). Long-lasting parasite spore banks have been found for other Daphnia microparasites and are likely to be important for disease dynamics (Ebert 1995;Ebert et al 1997;Decastaecker et al 2002Decastaecker et al , 2004.…”

Section: Discussion (A) Diapause Drives Prevalence Cyclesmentioning

confidence: 99%

Apparent seasonality of parasite dynamics: analysis of cyclic prevalence patterns

Lass

Ebert

2005

Proc. R. Soc. B.

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Seasonal disease dynamics are common in nature, but their causes are often unknown. Our case study provides insight into the cyclic prevalence pattern of the horizontally and vertically transmitted microsporidium Octosporea bayeri in its Daphnia magna host. Data from several populations over a four year period revealed a regular prevalence increase during summer and a decrease over winter when hosts underwent diapause. Prevalence also decreased after summer diapause indicating that the decline is causally linked to diapause rather than to winter conditions. Experiments showed that host diapause itself can explain a certain proportion of the decline. The decline further depends on the environmental conditions during diapause: infected resting eggs suffered from higher mortality under experimental winter than under experimental summer diapause conditions. Investigating the mechanisms of prevalence increase after diapause, the parasite was found to survive winter outside its host, enabling horizontal infection of susceptible hosts in the following growing season. Allowing for horizontal transmission in experimental host populations resulted in a steep prevalence increase, while excluding it led to a pronounced decline. Thus, the apparent seasonality in O. bayeri prevalence is characterized by a decline during host diapause followed by horizontal spread of the parasite during the host's asexual growth phase.

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Section: Discussion (A) Diapause Drives Prevalence Cyclesmentioning

confidence: 99%

Apparent seasonality of parasite dynamics: analysis of cyclic prevalence patterns

Lass

Ebert

2005

Proc. R. Soc. B.

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“…We ignore the death rate of the parasite during exposure, since P. ramosa spores can survive several decades (Decaestecker et al 2004).…”

Section: (B) Experimental Setupmentioning

confidence: 99%

A quantitative test of the relationship between parasite dose and infection probability across different host–parasite combinations

2008

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Epidemiological models generally assume that the number of susceptible individuals that become infected within a unit of time depends on the density of the hosts and the concentration of parasites (i.e. mass-action principle). However, empirical studies have found significant deviations from this assumption due to biotic and abiotic factors, such as seasonality, the spatial structure of the host population and host heterogeneity with respect to immunity and susceptibility. In this paper, we examine the effect of the dose level of the bacterial endoparasite Pasteuria ramosa on the infection rate of its host, the water flea Daphnia magna. Using seven host clones and two parasite isolates, we measure the fraction of infected hosts after exposure to eight different parasite doses to determine whether there is variation in the infection process across different host clone-parasite isolate combinations. In five combinations, a pronounced dose-dependent infection pattern was found. Using a likelihood approach, we compare the infection data of these five combinations to the fit of three mathematical models: a mass-action model, a parasite antagonism model (i.e. an increase in the parasite dose leads to an under-proportionate increase in the infection rate per host) and a heterogeneous host model. We found that the host heterogeneity model, in which we assumed the existence of non-inherited phenotypic differences in host susceptibilities to the parasite, provides the best fit. Our analysis suggests that among 5 out of the 14 host clone-parasite isolate combinations that resulted in appreciable infections, non-genetic host heterogeneity plays an important role.

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“…Despite their widespread occurrence (de Meeus and Renaud 2002) and importance in regulating predation and competition (Hatcher et al 2006), there are very few long-term or landscape-level studies on parasite population dynamics. Perhaps the best-known factors affecting parasite persistence are abiotic conditions (Morgan et al 2004, Tseng 2006, which can have powerful consequences for parasites with a vulnerable, free-living stage outside the host, even extirpating local populations (Decaestecker et al 2004, Cattadori et al 2005, Pascual and Dobson 2005. A second set of potentially powerful factors involve biotic interactions, such as competition among parasites Hudson 1986, Hatcher et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Metapopulation Dynamics Override Local Limits on Long‐term Parasite Persistence

Ram

Preisser

Gruner

et al. 2008

Ecology

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Abstract. A simple null model, particularly germane to small and vulnerable organisms such as parasites, is that local conditions set a stage upon which larger-scale dynamics play out. Soil moisture strongly influences survival of entomopathogenic nematodes (EPN), which in turn drive trophic cascades by protecting vegetation from root-feeding herbivores. In this study, we examine the mechanisms responsible for patchy occurrence of an entomopathogenic nematode, Heterorhabditis marelatus, in a California coastal prairie. One hypothesis proposes that biotic factors such as competition and natural enemies could regulate occurrence of EPN populations. We found that fungi and other enemies of EPN, although locally potent, did not explain the patterns of incidence across sites. Abiotic factors also have strong effects on EPN persistence, especially for vulnerable free-living stages. Thus, we tested the hypothesis that patchy occurrence of EPN on a large landscape was driven by differences in soil moisture.Our research uses long-term data on nematode incidence in combination with a landscapelevel experiment to demonstrate the lack of a correlation between soil moisture and long-term persistence. A year-long experiment showed EPN mortality was weakly correlated with soil moisture among our study sites. Thirteen years of data, however, showed that colonization rates were highly correlated with long-term persistence. Sites with highest long-term persistence experienced the highest rates of rhizosphere colonization, extinction, and turnover. As a result, we concluded that metapopulation dynamics override limitations set by local and short-term abiotic conditions to determine long-term persistence in this parasite-driven trophic cascade.

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Haunted by the past: Evidence for dormant stage banks of microparasites and epibionts of Daphnia

Cited by 59 publications

References 55 publications

Apparent seasonality of parasite dynamics: analysis of cyclic prevalence patterns

Apparent seasonality of parasite dynamics: analysis of cyclic prevalence patterns

A quantitative test of the relationship between parasite dose and infection probability across different host–parasite combinations

Metapopulation Dynamics Override Local Limits on Long‐term Parasite Persistence

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