Kelyn  Carlson,   '10 5
   Major: Biology
   Hometown: Grand Rapids, MI

Sponsor(s): Dean McCurdy
Support: FURSCA-Orpha Leiter Irwin Research Fellowship in Pre-Medicine, Pierce Cedar Creek Institute

Abstract: 
Amphibian populations are in decline worldwide and face threats from emerging infectious diseases. In the Great Lakes region, viral, bacterial, and fungal pathogens have been identified and connected to mass mortality events in amphibian populations, although relationships between parasitism, environmental conditions, and stress levels in frogs remain unclear. Using non-lethal methods, we tested green frogs (Rana clamitans) for the presence of the virus Ranavirus, and the opportunistic bacterium Aeromonas hydrophila at ponds in Western Michigan, USA. We also measured levels of the stress hormone corticosterone in plasma collected from frogs before and after the breeding season in 2008. Using PCR detection methods, we failed to detect Ranavirus in tissue samples, but prevalence of Aeromonas on frogs was high (>90%) in three years of study (2005, 2007, 2008) and colony counts increased over the breeding season. As expected, males had higher levels of corticosterone (measured using EIA kits) and frogs in lower body condition also exhibited higher stress hormone levels, but corticosterone levels did not vary significantly over time. Unusually high prevalence of Aeromonas on green frogs (20x that recorded in prior studies) does not seem to be associated with mass mortality of frogs in the populations we studied.

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