Loggerhead sea turtles are the latest microbe hosts

Photo: Goran/Adobe Stock

A loggerhead sea turtle near Brijuni National Park in Croatia.

The relationship between animal hosts and their microbial communities is vital to the animals’ development, physiology, immune response, metabolism, and reproduction. This relationship has recently gained more attention in sea turtles because human egg poaching, habitat disruptions, climate change, and accidental bycatch has increased their susceptibility to microbial changes. Conservation and rehabilitation efforts have increased interest in sea turtle gut, skin, nest, and egg microbiota.

A team of researchers from Croatia, Italy, and Austria, sparked by this interest, investigated the bacterial and fungal communities of loggerhead sea turtles belonging to the Adriatic Sea and published their findings with the Microbial Ecology Forum. The researchers found loggerheads of ranging ages at various points along the Adriatic Sea coast and brought them to locations where samples were collected or over 3 years. Investigators sequenced the samples’ ribosomal RNA to identify microbial and fungal species.

Previous research in this area focused on pathogenic bacteria and gut microbiota as it relates to hatching failure, rehabilitation efforts, plastic pollution, and various other points of interest. These investigators discovered more microbial diversity and fungal communities than were previously known, individual variation in microbes amongst the loggerheads, and a microbial exchange with the loggerhead environment.

The microbial and fungal communities had a few important characteristics. Distinct microbial communities occupied the carapace (top shell), cloacal (opening for feces, urine, and reproductive product removal, as well as breathing), and oral mucosa. Microbial communities were distinct to each sampling site and cloacal microbial diversity showed a negative correlation with turtle age and size. This correlation may be attributed to stronger bite force and diving capabilities developed in juvenile loggerheads. Fungal communities were highly heterogeneous among individual turtles and did not indicate patterns with regards to age or sex.

Because of shifts in turtle behavior leading to increased human interaction, understanding the microbial communities present within loggerhead sea turtles is important to anticipate risk, especially with bacterial and fungal pathogens. Even with increased interest and research into loggerhead microbiota, challenges to establishing a healthy microbiome persist. The investigators stressed that future studies should attempt to establish healthy loggerhead microbiomes at various developmental stages and consider the role of probiotics and prebiotics to improve conservation efforts.

Amanda Bean, BS, is a 2025 PharmD candidate studying veterinary pharmacy at the University of Connecticut School of Pharmacy in Storrs.

Reference

Filek K, Vuković BB, Žižek M, et al. Loggerhead sea turtles as hosts of diverse bacterial and fungal communities. Microb Ecol. 2024;87(1):79. doi:10.1007/s00248-024-02388-x