Indirect effects of a trematode parasite on a benthic community.
Bernot, Randall*,1, 1 Murray State University, Murray, KY
ABSTRACT- Parasites are ubiquitous components of food webs, yet the role of parasites in the structure and function of freshwater communities remains unclear. Many digenetic trematodes parasitize freshwater snails that are key components of lake and stream food webs. I investigated the effects of the trematode, Posthodiplostomum minimum, on a pulmonate snail, Physa acuta, and subsequent parasite effects on a benthic algal community. In individual grazing trials, trematode-infected snails grazed more rapidly than uninfected snails by 22%. In a laboratory experiment, P. minimum affected periphyton biomass and community structure. Experimental aquaria were stocked with periphyton-covered ceramic tiles and snail populations at trematode infection levels of 0%, 10%, and 50% infected. Periphyton biomass did not differ among aquaria with 0% and 10% snail infection. However, after 8 days, periphyton biomass was >30% lower in high-infection aquaria compared to other aquaria, presumably due to higher grazing rates of infected snails. Furthermore, filamentous green algae dominated high-infection aquaria; whereas diatoms were more prevalent in no- and low-infection aquaria. Thus, by altering snail grazing, a trematode altered snail-periphyton interactions and overall benthic community structure.
Key words: parasitism, aquatic, gastropod
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