Characterization of oral and cloacal microbial communities of wild and rehabilitated loggerhead sea turtles (Caretta caretta)

Klara Filek,Romana Gračan,Antonio Di Bello,Sunčica Bosak,Adriana Trotta,Marialaura Corrente

doi:10.1186/s42523-021-00120-5

Klara Filek, Romana Gračan + Show 4 more

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https://doi.org/10.1186/s42523-021-00120-5

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Abstract

BackgroundMicrobial communities of wild animals are being increasingly investigated to provide information about the hosts’ biology and promote conservation. Loggerhead sea turtles (Caretta caretta) are a keystone species in marine ecosystems and are considered vulnerable in the IUCN Red List, which led to growing efforts in sea turtle conservation by rescue centers around the world. Understanding the microbial communities of sea turtles in the wild and how affected they are by captivity, is one of the stepping stones in improving the conservation efforts. Describing oral and cloacal microbiota of wild animals could shed light on the previously unknown aspects of sea turtle holobiont biology, ecology, and contribute to best practices for husbandry conditions.ResultsWe describe the oral and cloacal microbiota of Mediterranean loggerhead sea turtles by 16S rRNA gene sequencing to compare the microbial communities of wild versus turtles in, or after, rehabilitation at the Adriatic Sea rescue centers and clinics. Our results show that the oral microbiota is more sensitive to environmental shifts than the cloacal microbiota, and that it does retain a portion of microbial taxa regardless of the shift from the wild and into rehabilitation. Additionally, Proteobacteria and Bacteroidetes dominated oral and cloacal microbiota, while Kiritimatiellaeota were abundant in cloacal samples. Unclassified reads were abundant in the aforementioned groups, which indicates high incidence of yet undiscovered bacteria of the marine reptile microbial communities.ConclusionsWe provide the first insights into the oral microbial communities of wild and rehabilitated loggerhead sea turtles, and establish a framework for quick and non-invasive sampling of oral and cloacal microbial communities, useful for the expansion of the sample collection in wild loggerhead sea turtles. Finally, our investigation of effects of captivity on the gut-associated microbial community provides a baseline for studying the impact of husbandry conditions on turtles’ health and survival upon their return to the wild.

Highlights

Microbial communities of wild animals are being increasingly investigated to provide information about the hosts’ biology and promote conservation
Wild animals are sensitive to environmental perturbations caused by climate change and anthropogenic habitat disruption, investigating wild animal-associated microbial communities contributes to improving existing conservation efforts [7, 8]
There are seven extant sea turtle species listed on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species [19]: Kemp’s ridley (Lepidochelys kempii) and hawksbill sea turtles (Eretmochelys imbricata) are critically endangered; the green turtle (Chelonia mydas) is considered to be endangered; loggerhead (Caretta caretta), olive ridley (Lepidochelys olivacea) and leatherback (Dermochelys coriacea) sea turtles are listed as vulnerable, while data are deficient for the flatback sea turtle (Natator depressus)

Summary

Introduction

Microbial communities of wild animals are being increasingly investigated to provide information about the hosts’ biology and promote conservation. Loggerhead sea turtles (Caretta caretta) are a keystone species in marine ecosystems and are considered vulnerable in the IUCN Red List, which led to growing efforts in sea turtle conservation by rescue centers around the world. Understanding the microbial communities of sea turtles in the wild and how affected they are by captivity, is one of the stepping stones in improving the conservation efforts. Most studies of microbial communities have focused on the distal gut of humans or captive mammals [2, 6] but there are recent growing efforts in investigations of. Marine mammals have been the focus of most vertebrate microbial community studies that undertook a wider sampling effort of body sites other than the distal gut or feces [12,13,14,15,16]. The efforts of sea turtle rescue and rehabilitation initiatives facilitate access for sea turtle-focused research [20] and, studies on microbial communities of sea turtles are increasing

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