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Isolation and molecular identification of pathogens causing sea turtle egg fusariosis in key nesting beaches in Costa Rica

Summary

Researchers in Costa Rica discovered that a dangerous fungal disease affecting sea turtle eggs is more widespread than previously known. The disease, called sea turtle egg fusariosis, is caused by two types of fungi that can kill developing turtle embryos. Scientists used advanced genetic testing to identify these fungi at major turtle nesting beaches on both coasts of Costa Rica, finding one fungus present at all locations while another was found only on the Caribbean coast. While the disease is not severely harming Costa Rican sea turtles yet, environmental changes could make it worse in the future.

Background

Sea turtle egg fusariosis (STEF) is an emerging fungal disease caused by Fusarium falciforme and Fusarium keratoplasticum that threatens endangered sea turtle populations globally. The disease is associated with high embryo mortality rates and represents a significant conservation challenge. Accurate identification of STEF-causing species is essential for guiding conservation efforts on important nesting beaches.

Objective

This study aimed to identify and characterize the presence of STEF-causing pathogens at four key nesting beaches in Costa Rica using multilocus sequence typing (MLST) analysis. The researchers conducted fungal isolations from sea turtle eggshells and nest sand to evaluate the distribution of Fusarium falciforme and Fusarium keratoplasticum across the Pacific and Caribbean coasts.

Results

Of 147 axenic cultures obtained, 47 (32%) belonged to STEF-causing species: Fusarium falciforme (n=32) and Fusarium keratoplasticum (n=15). Fusarium falciforme was detected across all study locations on both coasts, while Fusarium keratoplasticum was found exclusively in failed leatherback eggs at Pacuare on the Caribbean coast. This represents the first survey accurately identifying STEF-causing species in Costa Rica using MLST methodology.

Conclusion

The study confirms widespread presence of STEF-causing pathogens on Costa Rica’s main sea turtle nesting beaches, with Fusarium falciforme being more geographically distributed than Fusarium keratoplasticum. While STEF is not currently severely affecting Costa Rican sea turtles, various environmental factors could increase disease incidence, making monitoring and understanding pathogen distribution critical for conservation efforts.
  • Published in:PLoS One,
  • Study Type:Observational Survey,
  • Source: PMID: 40997043, DOI: 10.1371/journal.pone.0333280
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