The two Daphnia magna shown here are genetically identical sisters, born at the same time and raised in identical environments, but the one on the right is infected with the bacterium Pasteuria ramosa. A recent study in Proc. B. by biology postdoc Clay Cressler and faculty Bill Nelson, Troy Day and Ed McCauley (U Calgary) has uncovered why Pasteuria causes its host to stop reproducing and grow to twice its normal mass. The answer has to do with the flow of energy in the host. Pasteuria gets its energy from the resources the host allocates to growth: by forcing the host to put all of the energy it normally uses for reproducing into growing instead, Pasteuria increases its access to resources, indirectly increasing host growth in the process. This paper is the second in a series of papers, following on an Ecology Letters study published earlier this year, exploring the role of energy allocation in disease processes. For more information, click on links to the Science News piece on the paper or the links to either open access publication below.
Science News article: http://news.sciencemag.org/plants-animals/2014/08/castrated-water-fleas-grow-gigantic-proportions
Proceedings B paper: http://rspb.royalsocietypublishing.org/content/281/1792/20141087.abstract
Ecology Letters paper: http://onlinelibrary.wiley.com/doi/10.1111/ele.12229/abstract