Ecological Archives E087-096-A1

Lara J. Rachowicz, Roland A. Knapp, Jess A. T. Morgan, Mary J. Stice, Vance T. Vredenburg, John M. Parker, and Cheryl J. Briggs. 2006. Emerging infectious disease as a proximate cause of amphibian mass mortality. Ecology 87:1671–1683.

Appendix A. Reliability of jaw sheath depigmentaion as an indicator of chytridiomycosis.

To evaluate the reliability of jaw sheath depigmentation as an indicator of chytridiomycosis, we conducted a study in which we compared the extent of jaw sheath depigmentation in R. muscosa tadpoles at individual sites with the result of PCR assays conducted on one or more R. muscosa specimens from the same site. These results are described in detail in Knapp and Morgan (2006) and are summarized here. Mouthpart inspections were conducted in 2003 and 2004 and included a total of at least five tadpoles from each of 82 sites. One or more of the inspected tadpoles was collected from each site and subjected to real-time PCR assays of B. dendrobatidis presence/absence (see Appendix B for details of the real-time PCR methods).

Comparisons of the site-specific extent of upper jaw sheath pigmentation (0–100%, averaged across all inspected tadpoles at a site) with results from PCR assays indicated a close correspondence between disease status as determined from mouthpart inspections and PCR assays. Of the tadpoles collected from sites with an average jaw sheath pigmentation score of 100%, 0 of 38 (0%) were B. dendrobatidis-positive. In contrast, of the tadpoles collected from sites with average jaw sheath pigmentation scores of <100%, 37 of 44 (84%) were B. dendrobatidis-positive. Therefore, using a rule that sites with an average jaw sheath pigmentation score of 100% are not infected and those with scores <100% are infected would produce an overall misclassification rate of 8% (rate of false-negatives = 0% (0/38), rate of false-positives = 16% (7/44)). Therefore, the jaw sheath pigmentation score we used to categorize sites as B. dendrobatidis-positive or negative provides a reasonably accurate measure of site-specific B. dendrobatidis status.

LITERATURE CITED

Knapp, R. A., and J. A. T. Morgan. 2006. Tadpole mouthpart depigmentation as an accurate indicator of chytridiomycosis, an emerging disease of amphibians. Copeia 2006:188–197.



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