DNA Barcoding as a Means to Identify Organisms associated with Amphibian Eggs

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Biological Sciences

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Water molds, primarily in the genus Saprolegnia, have been implicated in large-scale mortality of amphibian eggs under a variety of environmental conditions. Although a number of water mold species infect amphibian eggs, the pathogens identified from die-offs or utilized in ecological studies often remain unidentified or identified as only one of two species (S. ferax and S. parasitica). Lack of adequate identification makes it difficult to assess factors of the host-parasite interaction that contribute to saprolegniasis in amphibians. We obtained isolates from three species of amphibian eggs and used traditional morphological characteristics and a DNA barcoding procedure to evaluate both types of identification. Traditional morphological identifications performed poorly and resulted in a number of apparent misidentifications and the failure to identify morphologically cryptic species associated with amphibian eggs. In addition, a large number of apparent species synonyms are in use. While DNA barcoding did not allow firm assignment of species names, the approach adequately assigned isolates to well-supported groupings. This phylogenetic approach should allow the eventual assignment of appropriate binomial names as we accumulate a larger more reliable database. These data also suggest that these pathogens require precise identification because we isolated multiple species of water molds from all three amphibian species. Further, we isolated some pathogens from only one of the three amphibian species. We recommend that future studies on amphibian saprolegniasis include DNA barcoding information for the pathogens to facilitate studies of host specificity and pathogenicity.


This article was originally published Open Access in Herpetological Conservation and Biology. The full-text article from the publisher can be found here.


Herpetological Conservation and Biology


Copyright © 2008. James E. Johnson. All rights reserved.