Trachemys scripta Eggs as Part of a Potential In Vivo Model for Studying Sea Turtle Egg Fusariosis

Summary

Sea turtles around the world face a serious threat from a fungal disease called fusariosis that destroys their eggs before they hatch. Scientists wanted to study how this fungus causes disease, but working with endangered sea turtles in tropical regions is difficult and heavily regulated. They discovered they could use eggs from red-eared slider turtles, an invasive species, as a substitute model to understand how the fungus infects eggs. The research showed that the fungus is highly virulent and modifies the acidity of egg surfaces to help it grow, providing valuable insights that could help protect endangered sea turtles.

Background

Sea turtle egg fusariosis (STEF) is an emerging fungal disease caused by Fusarium keratoplasticum and Fusarium falciforme that affects sea turtle eggs worldwide, resulting in low hatching success and mass mortalities. Research on this disease is challenging to conduct in natural settings due to environmental conditions in tropical regions and permit restrictions for threatened species. Identifying suitable model organisms is critical for advancing understanding of fungal pathogenicity and virulence mechanisms.

Objective

This study investigated the potential use of red-eared slider turtle (Trachemys scripta) eggs as an in vivo host model to study the biological properties of STEF pathogens. The research aimed to demonstrate that T. scripta eggs could replicate STEF disease signs, fulfill Koch’s postulates, and reveal pathogenic characteristics including virulence properties and pH modulation abilities.

Results

Fourteen of 15 inoculated eggs (93.3%) showed STEF signs compared to 33.3% in control 1 and 53.3% in control 2, with significantly higher disease severity in inoculated eggs. F. keratoplasticum was successfully reisolated from diseased eggs, confirming Koch’s postulates. The pathogen alkalinized infected egg surfaces (pH 8.0-9.0) while acidifying peptone glucose liquid media to pH 4.35, demonstrating pH modulation dependent on carbon availability.

Conclusion

Trachemys scripta eggs serve as a practical and effective in vivo host model for studying STEF-causing pathogens. F. keratoplasticum exhibits high virulence properties and pH-modulating capabilities that facilitate host colonization. This model system provides valuable opportunities for further research on pathogenic mechanisms and development of preventive strategies for this emerging fungal disease.
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