Wednesday, May 28, 2008 - 9:45 AM
376

Is habitat type a useful predictor of the susceptibility of local populations of tubifex tubifex to myxobolus cerebralis?

Julie D. Alexander1, Billie L. Kerans1, and Todd M. Koel2. (1) Department of Ecology, Montana State University, 310 Lewis Hall, Bozeman, MT 59715, (2) Yellowstone National Park, PO Box 168, Yellowstone Park, WY 82190

The aquatic oligochaete Tubifex tubifex is the intermediate host for the parasite, Myxobolus cerebralis, which causes salmonid whirling disease.  Although the relationship between disease severity in salmonids and infection in tubificid hosts is not well understood, previous research suggests that genetic variation within local stream populations of T. tubifex may be an important determinant of parasite success.  Our goals were to examine relationships between habitat features and abundance, infection prevalence, genetic diversity and susceptibility of T. tubifex in Yellowstone cutthroat trout spawning tributaries in Yellowstone National Park, where M. cerebralis was detected in 1998.  Abundance of tubificids and T. tubifex, and infection prevalence were positively correlated with fine sediments and organic matter, which characterized unconfined habitats.  Little mitochondrial genetic diversity was detected among T. tubifex assemblages; however, eight strains were identified using RAPDs, two of which were commonly infected.  We have assessed the susceptibility of four of these strains in the laboratory.  All strains were susceptible to infection; however, strains associated with high-risk (unconfined) habitats amplified the parasite more than strains associated with low-risk (confined) habitats.  Thus, there may be an association between habitat type and differences in susceptibility among genetically variable T. tubifex.


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