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- Title
Virulence of parasites in hosts under environmental stress: experiments with anoxia and starvation.
- Authors
Jokela, Jukka; Taskinen, Jouni; Mutikainen, Pia; Kopp, Kirstin
- Abstract
Most environments periodically impose severe stress that may cause high mortality and alter population structure, for example, by removing sick and old individuals. We examined how anoxic conditions and starvation of the host affect virulence of two closely related trematode parasites,Rhipidocotyle campanulaandR. fennica. These parasites differ by prevalence of infection and by exploitation rate of individual hosts (freshwater clam,Anodonta piscinalis). Infection byR. campanulais rare (<5% prevalence of infection) and destroys on average 90% of the gonad tissue of the individual host. Infection byR. fennicais more common (20–60% prevalence of infection) and leads to on average 30% gonad destruction. In the end, both infections lead to host infertility. We predicted thatR. campanulainduces higher host mortality thanR. fennicaunder host stress. In two laboratory experiments, we exposed naturally-infected and uninfected clams to anoxia and to starvation. Anoxia occasionally takes place during winter in eutrophic lakes, while some degree of starvation should occur seasonally. We found that mortality rate of clams was much higher under anoxia than under starvation, and that infection increased mortality rate under both types of host stress. As predicted,R. campanulainduced higher host mortality thanR. fennica. Host survival was population-specific, suggesting that clams of different origins carried different amount of energy reserves. Severe environmental perturbation may removeR. campanulainfected individuals from the host population, but recolonization from the fish host is likely to prevent extinction of the parasite suprapopulation. The observed high host mortality induced byR. campanulamay be one ecological explanation for the consistently lower prevalence of infection ofR. campanulawhen compared toR. fennica.
- Subjects
ENVIRONMENTAL engineering; HYPOXEMIA; STARVATION; PARASITES; MICROBIAL virulence
- Publication
Oikos, 2005, Vol 108, Issue 1, p156
- ISSN
0030-1299
- Publication type
Article
- DOI
10.1111/j.0030-1299.2005.13185.x