Saprolegniaceae identified on amphibian eggs throughout the Pacific Northwest, USA, by internal transcribed spacer sequences and phylogenetic analysis

Abstract

We assessed the diversity and phylogeny of Saprolegniaceae on amphibian eggs from the Pacific Northwest, with particular focus on Saprolegnia ferax, a species implicated in high egg mortality. We identified isolates from eggs of six amphibians with the internal transcribed spacer (ITS) and 5.8S gene regions and BLAST of the GenBank database. We identified 68 sequences as Saprolegniaceae and 43 sequences as true fungi from at least nine genera. Our phylogenetic analysis of the Saprolegniaceae included isolates within the genera Saprolegnia, Achlya and Leptolegnia. Our phylogeny grouped S. semihypogyna with Achlya rather than with the Saprolegnia reference sequences. We found only one isolate that grouped closely with S. ferax, and this came from a hatchery-raised salmon (Idaho) that we sampled opportunistically. We had representatives of 7–12 species and three genera of Saprolegniaceae on our amphibian eggs. Further work on the ecological roles of different species of Saprolegniaceae is needed to clarify their potential importance in amphibian egg mortality and potential links to population declines.

• Achlya
• amphibian decline
• egg
• lake
• Leptolegnia
• oomycete
• Saprolegnia ferax
• S. semihypogyna

This work was supported by the Idaho National Engineering and Environmental Laboratory (now INL) Education Outreach BBW Bechtel grant and a grant from the US Geological Survey Amphibian Research and Monitoring Initiative (ARMI). We thank V. Winston for his contributions throughout this project and G. Carroll for his thoughtful review of an earlier version of this manuscript. Samples were gathered under scientific collecting permits from the National Park Service, Washington Department of Fish and Wildlife, Oregon Department of Fish and Wildlife, Idaho Department of Fish and Game and Montana Department of Fish and Wildlife. We thank R. Hoffman (USGS FRESC), B. Samora (Mount Rainier National Park), P. Murphy (Idaho Department of Fish and Game) and B. Maxell (Montana National Heritage Program) for help identifying sampling sites. We thank S. Galvan for assembling the map and B. Cummings, J. Jones, J. Kittrell, B. McCreary, J. Oertley and C. Rombough for assistance in the field.