The Effects of Chytridiomycosis on Myocardial Oxygenation in Columbian Spotted Frogs (Rana luteiventris)

Abstract

Chytridiomycosis is an infection in amphibians caused by the fungus Batrachochytrium dendrobatidis that has been linked to world-wide amphibian decline. However, there is currently no clear explanation of how this infection is killing amphibians. I hypothesize that the fungus is preventing effective cutaneous gas exchange, causing hypoxia in the heart which could lead to myocardial ischemia. The objectives of this study are to find an organism that is susceptible to Chytridiomycosis which can be used as a model for detecting myocardial ischemia in frogs and to establish a protocol for ischemia detection. Rana luteiventris (Columbian Spotted Frogs) were collected and swabbed from two Montana lakes. Of the 23 total frogs sampled two from Park Lake and one from Krohn Lake tested positive for B. dendrobatidis according to a Taqman quantitative PCR assay. Captive R. luteiventris inoculated with the fungus showed signs of infection. A spleen sample was collected from a frog with artificially compromised cutaneous gas exchange. This sample was run out on a 10% polyacrylamide native gel and stained for LDH activity. When compared to a control spleen sample the frog with the compromised cutaneous gas exchange showed a 6.4% increase in Heart-type LDH indicating possible myocardial damage. In conclusion, the detection of Chytridiomycosis in wild-caught R. luteiventris and the results of the inoculations indicate that this species is an acceptable model organism. The established protocol using LDH isoenzyme native gels shows promise of being an effective method of assessing myocardial damage in amphibians.