Shell lesion prevalence and bacteriome associations in threatened western pond turtles (Actinemys marmorata and Actinemys pallida) in California, USA
Western pond turtles in the San Francisco Bay Area face widespread shell lesions, yet the microbial patterns underlying these conditions remain poorly understood. Sampling turtles from six ponds, researchers compared bacteriomes from whole‑shell swabs and keratin scrapes and assessed lesion types using photographic inspections. While alpha diversity did not differ between turtles with and without lesions, swabs showed higher richness than scrapes. Keratin‑associated bacterial composition was strongly influenced by pond location and lesion presence, with turtles exhibiting lesions showing higher relative abundances of Actinobacteriota, Bacteroidota, Cyanobacteria and Deinococcota. Because western pond turtles are under consideration for Endangered Species Act listing, identifying microbial signatures linked to shell disease is essential for conservation and management.
Subject Tags
- Biodiversity
- Wildlife
- Health
Abstract
Bacteriome characterization studies can provide insights into the microbial ecology associated with disease. We collected western pond turtles (Actinemys marmorata and Actinemys pallida) from six San Francisco Bay Area, California, USA, ponds; assessed their shells for lesions; and collected shell swabs and keratin scrape samples to evaluate bacteriome differences between the whole shell (swabs) and the affected tissues (scrapes). We quantified shell lesion type and prevalence by using visual inspections of photographs collected of the plastron and carapace and then applied 16S rRNA amplicon sequencing to characterize the associated bacteriomes of shells that observed pits, ulcerations, or no lesions. We observed shell lesions at high frequencies throughout our sites, with larger individuals (>100-mm plastron length) more likely to possess injuries. We saw no differences in alpha diversities between shells presenting with lesions and those on which we did not observe lesions; however, swab samples showed higher bacterial richness than keratin scrapes. The bacterial composition within the scrapes was influenced by pond location and then lesion presence. We observed a higher relative abundance of Actinobacteriota, Bacteroidota, Cyanobacteria and Deinococcota in the shell keratin microflora of turtles with shell lesions. Because western pond turtles are under consideration for listing under the Endangered Species Act of 1973 in the USA, understanding patterns of shell disease pathologies and the bacteria associated with disease is imperative for the management of current populations.
Citation
Green, N., Norwood, A., Sidhe, C., Mutlow, A., Aymen, J., Stiles, R., ... & Hernández-Gómez, O. (2025). Shell Lesion Prevalence and Bacteriome Associations in Threatened Western Pond Turtles (Actinemys marmorata and Actinemys pallida) in California, USA. The Journal of Wildlife Diseases, 61(3), 574-586. https://doi.org/10.7589/JWDD-24-00142
TNC Authors
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Max R. Lambert
Director of Science, Washington
The Nature Conservancy
Email: max.lambert@tnc.org