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Aquatic Microbial Ecology

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AME 63:265-272 (2011)  -  DOI:

Spatiotemporal dynamics of free-living stages of a bacterial parasite of zooplankton

Sara H. Thomas1,4, Christopher Bertram2, Karla van Rensburg1, Carla E. Cáceres2,3, Meghan A. Duffy1,*

1School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
2Program in Ecology, Evolution and Conservation Biology, and 3School of Integrative Biology, University of Illinois, Urbana-Champaign, Illinois 61820, USA
4Present address: Marietta High School, 1171 Whitlock Ave SW, Marietta, Georgia 30064, USA
*Corresponding author. Email:

ABSTRACT: Parasites are generally thought of as being intimately tied to their hosts, yet many ­parasites produce free-living stages. This raises the question: what are parasites doing when they are not being parasitic? We studied the spatiotemporal dynamics of free-living infectious stages and asked whether these dynamics were correlated with infections in 2 focal host species. We used a common and virulent bacterial parasite, Spirobacillus cienkowskii, which infects Daphnia spp. Densities of free-living infective stages were high in a stratified, eutrophic lake (up to ~105 to 106 cells l–1), but also spatiotemporally variable. There was a positive correlation between the density of these free-­living stages and the prevalence of infected Daphnia on the subsequent sampling date. This suggests that free-living stages increase in environmental reservoirs prior to the start of epidemics in Daphnia. We also studied the ability of free-living stages to persist outside their hosts for long periods of time. In laboratory microcosms, we found that S. cienkowskii persisted under simulated environmental conditions for more than 2 mo, before declining to below our method’s detection limit after approximately 3 mo. Overall, our study of a common parasite of Daphnia reveals the potential importance of free-living stages to epidemic dynamics, and suggests that it is important to consider environmental reservoirs when studying disease dynamics.

KEY WORDS: Spores · Daphnia dentifera · Daphnia pulicaria · Curse of the pharaoh · qPCR · ­Environmental transmission · Pathogen

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Cite this article as: Thomas SH, Bertram C, van Rensburg K, Cáceres CE, Duffy MA (2011) Spatiotemporal dynamics of free-living stages of a bacterial parasite of zooplankton. Aquat Microb Ecol 63:265-272.

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