Limits...
Starvation reveals the cause of infection-induced castration and gigantism.

Cressler CE, Nelson WA, Day T, McCauley E - Proc. Biol. Sci. (2014)

Bottom Line: Because these processes will affect both host and parasite fitness, it can be challenging to determine who benefits from them.Our results show that starvation primarily affects investment in reproduction, and increasing starvation stress reduces gigantism and parasite fitness without affecting castration.These results are consistent with an energetic structure where the parasite uses growth energy as a resource.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Queen's University, Kingston, Ontario, Canada cressler@queensu.ca.

ABSTRACT
Parasites often induce life-history changes in their hosts. In many cases, these infection-induced life-history changes are driven by changes in the pattern of energy allocation and utilization within the host. Because these processes will affect both host and parasite fitness, it can be challenging to determine who benefits from them. Determining the causes and consequences of infection-induced life-history changes requires the ability to experimentally manipulate life history and a framework for connecting life history to host and parasite fitness. Here, we combine a novel starvation manipulation with energy budget models to provide new insights into castration and gigantism in the Daphnia magna-Pasteuria ramosa host-parasite system. Our results show that starvation primarily affects investment in reproduction, and increasing starvation stress reduces gigantism and parasite fitness without affecting castration. These results are consistent with an energetic structure where the parasite uses growth energy as a resource. This finding gives us new understanding of the role of castration and gigantism in this system, and how life-history variation will affect infection outcome and epidemiological dynamics. The approach of combining targeted life-history manipulations with energy budget models can be adapted to understand life-history changes in other disease systems.

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Carbon accounting in infected animals. (a) The solid line shows the 1 : 1 relationship between the expected carbon freed up by castration and the observed carbon in gigantism and parasite spores. (b) The solid line shows the 1 : 1 relationship between observed carbon in gigantism and in spores. Colours denote the feeding interval treatment as in figure 3.
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RSPB20141087F4: Carbon accounting in infected animals. (a) The solid line shows the 1 : 1 relationship between the expected carbon freed up by castration and the observed carbon in gigantism and parasite spores. (b) The solid line shows the 1 : 1 relationship between observed carbon in gigantism and in spores. Colours denote the feeding interval treatment as in figure 3.

Mentions: Simple carbon accounting further illustrates the connection between host size and spore load. Figure 4 shows the relationship between the amount of carbon ‘liberated’ by castration and the amount of carbon observed in gigantism and spores. The carbon liberated by castration is calculated as the difference between the expected amount of carbon in eggs for a control animal in each treatment and the observed carbon in eggs for each infected animal. The amount of carbon in gigantism is calculated as the difference between the observed size of each infected animal and the expected size for a control animal in each treatment. Across feeding treatments, the data show a strong correlation between the amount of carbon liberated by castration and the amount ending up in extra host tissue and spores (figure 4a; Pearson's r = 0.77). The data also suggest that host growth and parasites end up with nearly equal amounts of liberated carbon (figure 4b; Pearson's r = 0.68). The black line shows the one-to-one relationship in both panels of figure 4.Figure 4.


Starvation reveals the cause of infection-induced castration and gigantism.

Cressler CE, Nelson WA, Day T, McCauley E - Proc. Biol. Sci. (2014)

Carbon accounting in infected animals. (a) The solid line shows the 1 : 1 relationship between the expected carbon freed up by castration and the observed carbon in gigantism and parasite spores. (b) The solid line shows the 1 : 1 relationship between observed carbon in gigantism and in spores. Colours denote the feeding interval treatment as in figure 3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150321&req=5

RSPB20141087F4: Carbon accounting in infected animals. (a) The solid line shows the 1 : 1 relationship between the expected carbon freed up by castration and the observed carbon in gigantism and parasite spores. (b) The solid line shows the 1 : 1 relationship between observed carbon in gigantism and in spores. Colours denote the feeding interval treatment as in figure 3.
Mentions: Simple carbon accounting further illustrates the connection between host size and spore load. Figure 4 shows the relationship between the amount of carbon ‘liberated’ by castration and the amount of carbon observed in gigantism and spores. The carbon liberated by castration is calculated as the difference between the expected amount of carbon in eggs for a control animal in each treatment and the observed carbon in eggs for each infected animal. The amount of carbon in gigantism is calculated as the difference between the observed size of each infected animal and the expected size for a control animal in each treatment. Across feeding treatments, the data show a strong correlation between the amount of carbon liberated by castration and the amount ending up in extra host tissue and spores (figure 4a; Pearson's r = 0.77). The data also suggest that host growth and parasites end up with nearly equal amounts of liberated carbon (figure 4b; Pearson's r = 0.68). The black line shows the one-to-one relationship in both panels of figure 4.Figure 4.

Bottom Line: Because these processes will affect both host and parasite fitness, it can be challenging to determine who benefits from them.Our results show that starvation primarily affects investment in reproduction, and increasing starvation stress reduces gigantism and parasite fitness without affecting castration.These results are consistent with an energetic structure where the parasite uses growth energy as a resource.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Queen's University, Kingston, Ontario, Canada cressler@queensu.ca.

ABSTRACT
Parasites often induce life-history changes in their hosts. In many cases, these infection-induced life-history changes are driven by changes in the pattern of energy allocation and utilization within the host. Because these processes will affect both host and parasite fitness, it can be challenging to determine who benefits from them. Determining the causes and consequences of infection-induced life-history changes requires the ability to experimentally manipulate life history and a framework for connecting life history to host and parasite fitness. Here, we combine a novel starvation manipulation with energy budget models to provide new insights into castration and gigantism in the Daphnia magna-Pasteuria ramosa host-parasite system. Our results show that starvation primarily affects investment in reproduction, and increasing starvation stress reduces gigantism and parasite fitness without affecting castration. These results are consistent with an energetic structure where the parasite uses growth energy as a resource. This finding gives us new understanding of the role of castration and gigantism in this system, and how life-history variation will affect infection outcome and epidemiological dynamics. The approach of combining targeted life-history manipulations with energy budget models can be adapted to understand life-history changes in other disease systems.

Show MeSH
Related in: MedlinePlus