Sublethal Parasites and Host Energy Budgets: Tapeworm Infection in White‐Footed Mice

Abstract

One way to study a parasite's effect on the individual and population ecology of its host is to examine effects on the host's energy budget. A relatively innocuous effect of a gut parasite, such as decreased digestive efficiency, can potentially translate into an effect costly to host fitness, such as decreased reproduction, if other compensations (such as increased rate of food intake) do not occur. We found that infection by the tapeworm Hymenolepis citelli caused a 2% drop in dry—matter digestibility in host white—footed mice (Peromyscus leucopus). A crowding experiment indicated that this result should be applicable to a wide range of intensities of infection. However, we detected no compensation for this decreased digestive efficiency either in amount of food consumed or in mass change (which would indicate use of fat stores or changes in growth). In field experiments we used doubly labeled water to measure effects of tapeworms on field metabolic rate and water influx (potentially a measure of food intake rate), and temperature—sensitive transmitters to measure body temperature. We detected no compensations via these routes either. Our failure to detect compensations indicates that in the nonreproductive mice studied the decrease in digestive efficiency is not of sufficient importance to engender substantial compensations and is therefore unlikely to lead to fitness—altering effects. It is in reproductive animals or in animals subjected to food shortage that such effects would be expected.

Moderate Echinostoma trivolvis Infection Has No Effects on Physiology and Fitness-Related Traits of Larval Pickerel Frogs (Rana palustris)

“…However, we predicted such changes would only occur if energy demands were elevated which, based on the SMR results, does not seem to be the case. In addition, generous rations provided to individually maintained tadpoles might have hindered our ability to detect intestinal plasticity because it eliminated the need to develop a more-efficient digestive system to maintain optimal growth rates (Munger and Karasov, 1989). Therefore, we postulate that plasticity of the intestines remains a plausible response to parasitism in tadpoles.…”

An Experimental Study on the Effects of Polymorphiasis in Common Eider Ducklings

“…Potentially, parasites can affect the population size of their host through various direct and indirect mechanisms. Parasites may cause mortality, disease that renders their hosts more susceptible to predation and infectious agents, nutritional stresses, and reduced reproductive success (Munger and Karasov, 1989;Toft, 1991;Gulland, 1995). Parasites with low or moderate virulence and high transmission rates have been considered potentially most effective as long-term regulators of host population size (Anderson, 1979).…”

Primates and the Ecology of their Infectious Diseases: How will Anthropogenic Change Affect Host-Parasite Interactions?

“…40 Some parasites extract significant amounts of nutrients from hosts, resulting in marked reduction in energy uptake, 41 but others appear to have little or no effect on host energetics. 42,43 Animal body condition and reproductive status can be compromised when parasites inflict substantial energetic costs. 44 However, parasites do not necessarily induce negative effects if hosts have adequate energy reserves or nutrient supplies concurrent with infection, 32,35,42 suggesting that the outcome of host-parasite associations may be contingent on host nutritional status and infection severity.…”