Loggerhead Sea Turtles Harbor Diverse Bacteria and Fungi

Greg Howard
31st May, 2024

Loggerhead Sea Turtles Harbor Diverse Bacteria and Fungi

Image Source: Natural Science News, 2024

Key Findings

  • The study focused on the microbial communities of loggerhead sea turtles in the Adriatic Sea
  • Bacterial diversity in the turtles' distal gut decreases with age
  • Tenacibaculum species are more abundant in juvenile turtles than in adults
Research on microbial communities associated with wild animals provides a valuable reservoir of knowledge that could be used for enhancing their rehabilitation and conservation. The loggerhead sea turtle (Caretta caretta) is a globally distributed species with its Mediterranean population categorized as least concern according to the IUCN Red List of Threatened Species as a result of robust conservation efforts. In our study, we aimed to further understand their biology in relation to their associated microorganisms. We investigated epi- and endozoic bacterial and endozoic fungal communities of cloaca, oral mucosa, carapace biofilm. Samples obtained from 18 juvenile, subadult, and adult turtles as well as 8 respective enclosures, over a 3-year period, were analysed by amplicon sequencing of 16S rRNA gene and ITS2 region of nuclear ribosomal gene. Our results reveal a trend of decreasing diversity of distal gut bacterial communities with the age of turtles. Notably, Tenacibaculum species show higher relative abundance in juveniles than in adults. Differential abundances of taxa identified as Tenacibaculum, Moraxellaceae, Cardiobacteriaceae, and Campylobacter were observed in both cloacal and oral samples in addition to having distinct microbial compositions with Halioglobus taxa present only in oral samples. Fungal communities in loggerheads’ cloaca were diverse and varied significantly among individuals, differing from those of tank water. Our findings expand the known microbial diversity repertoire of loggerhead turtles, highlighting interesting taxa specific to individual body sites. This study provides a comprehensive view of the loggerhead sea turtle bacterial microbiota and marks the first report of distal gut fungal communities that contributes to establishing a baseline understanding of loggerhead sea turtle holobiont. The loggerhead sea turtle (Caretta caretta) is a species of significant conservation interest. While conservation efforts have led to a stabilized population in the Mediterranean, understanding the microorganisms associated with these turtles can further enhance their rehabilitation and conservation. The University of Zagreb conducted a study to explore the bacterial and fungal communities associated with different body sites of loggerhead sea turtles[1]. The study involved analyzing samples from 18 juvenile, subadult, and adult turtles, as well as their enclosures, over a three-year period. The researchers used amplicon sequencing of the 16S rRNA gene and the ITS2 region of the nuclear ribosomal gene to identify microbial communities. They found that the diversity of bacterial communities in the distal gut decreased with the age of the turtles. Specifically, Tenacibaculum species were more abundant in juveniles than in adults. Additionally, the study identified different bacterial taxa such as Tenacibaculum, Moraxellaceae, Cardiobacteriaceae, and Campylobacter in both cloacal and oral samples. Halioglobus taxa were found exclusively in oral samples. The fungal communities in the cloaca varied significantly among individuals and were distinct from those in the tank water. This study builds on previous research that has highlighted the importance of microbial communities in animal biology. For instance, earlier studies have shown that bacteria play a crucial role in the development and homeostasis of animals[2]. The microbiome can also shape host traits and influence evolutionary potential[3]. In the context of sea turtles, previous research has primarily focused on macro-epibiotic communities, such as diatoms, but has largely ignored their micro-epibiotic counterparts[4]. This study fills that gap by providing a comprehensive view of the bacterial and fungal microbiota associated with loggerhead sea turtles. Moreover, understanding these microbial communities is essential for conservation efforts. All sea turtle populations in the United States are listed as threatened or endangered, and identifying methods to support their health and prevent disease is crucial[5]. The study's findings can help develop strategies for maintaining a healthy microbiome in loggerhead sea turtles, thereby enhancing their rehabilitation and conservation. In summary, the study conducted by the University of Zagreb provides valuable insights into the microbial communities associated with loggerhead sea turtles. It reveals a trend of decreasing bacterial diversity in the distal gut with age and identifies specific bacterial and fungal taxa associated with different body sites. These findings contribute to a better understanding of the loggerhead sea turtle holobiont and offer potential avenues for improving their conservation and rehabilitation.

Animal ScienceMarine Biology


Main Study

1) Loggerhead Sea Turtles as Hosts of Diverse Bacterial and Fungal Communities

Published 30th May, 2024


Related Studies

2) Animals in a bacterial world, a new imperative for the life sciences.


3) The microbiome extends host evolutionary potential.


4) Epibiotic Diatoms Are Universally Present on All Sea Turtle Species.


5) What lives on and in the sea turtle? A literature review of sea turtle bacterial microbiota.


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