Conservation rearing programs for Washington state-endangered Western Pond Turtles (Actinemys marmorata) occur in managed habitats and have been successful in promoting population recovery over the past 20 years. However, this species’ recovery in Washington is currently being threatened by a disease causing shell lesions associated with a recently detected fungal pathogen (Emydomyces testavorans). Artificial animal environments include intensive management (e.g. disinfection) that limits microbial abundance and diversity. While intensively-managed environments are intended to reduce exposure to potential pathogens, they may also reduce potential microbiome benefits as diverse environmental and host microbiomes allow few available ecological niches. Thus, diverse microbiomes are expected to limit pathogen colonization and encourage robust immune systems. Our objective is to determine if the rearing environment microbiome influences the host microbiome and the susceptibility of Western Pond Turtles to shell disease.
Microbial communities associated with major habitat elements, turtle shells, and turtle cloacae were characterized from natural and managed habitats, including experimental biofilter and outdoor treatments intended to enhance microbial diversity. Environmental and turtle microbiomes were described using bacterial 16S rRNA gene and fungal internal transcribed spacer (ITS) DNA sequencing. Major taxa and microbial diversity were evaluated using analyses within the phyloseq and DESeq2 R packages.
Results/Conclusions
Conservation rearing environments exhibited reduced microbial species richness (ANOVA, p<0.001) and harbored distinct microbial populations relative to natural environments (PERMANOVA R2 = 0.28-0.34, p=0.001). In addition, the managed biofilter treatment and natural habitat environments had a lower relative abundance of E. testavorans compared to the conventional management treatment environment (p<0.001). While the biofilter treatment did not enrich microbial diversity and alter microbial community composition to resemble that of the natural environment specifically, this treatment was successful in significantly reducing the relative abundance of E. testavorans in the conservation rearing habitat, which has the long-term potential to improve health outcomes for turtles in this conservation rearing program.
The practical applications of this project serve to increase the efficacy of intensive rearing efforts in species recovery programs, thereby improving conservation efforts. Furthermore, this study has long-term implications for the future success of conservation rearing and release programs: improving habitat management practices through the cultivation of appropriate microbiomes will enable these animals, and conservation programs as a whole, to have the greatest chance to prevent extinction of endangered species.