Comparative analysis of the fecal bacterial communities of hawksbill sea turtles (Eretmochelys imbricata) and green sea turtles (Chelonia mydas)

Blood and cloacal microbiome profile of captive green turtles (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata): Water quality and conservation implications

In this study, we studied the environment factors such as plastics and heavy metals affecting the blood and cloacal microbiome of green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) in captivity. By non-metric multidimensional scaling analysis, data has shown that the environment factors (p = 0.02), rather than species differences (p = 0.06), significantly influenced the composition of the cloacal microbiota of green and hawksbill turtles. The cloacal microbiota of both captive green and hawksbill turtles was dominated by several similar dominant phyla at differential abundance. Green turtles' cloacal microbiome was made up of 46% of Proteobacteria, 31% of Bacteroidota, 11% of Campylobacterota and 4% of Firmicutes, while the hawksbill turtles' cloacal microbiome was made up of 33% of Bacteroidota, 18% of Firmicutes, 17% of Proteobacteria, and 2% of Campylobacterota. Water conductivity, salinity, microplastic polymers (polycarbonate, polyethylene terephthalate, polystyrene), and copper are positively associated (p < 0.05) with blood urea nitrogen. Hematocrit and hemoglobin were found also negatively correlated (p < 0.05) with water pH, polyethylene terephthalate, iron, lead and zinc. The correlations established in this study shed light on the intricate interplay between water quality and the physiological responses of sea turtles. Recognizing these relationships is pivotal for monitoring and preserving the well-being of sea turtles in their natural habitats.

Culture-Independent Species-Level Taxonomic and Functional Characterisation of Bacteroides, the Core Bacterial Genus Within Reptile Guts

The genus Bacteroides is a widespread and abundant bacterial taxon associated with gut microbiotas. Species within Bacteroides fill many niches, including as mutualists, commensals and pathogens for their hosts. Within many reptiles, Bacteroides is a dominant, 'core' gut bacterium that sometimes exhibits increased abundance in times of food scarcity, such as during hibernation. Here, we take a two-pronged approach to better characterise Bacteroides populations in reptile guts. Firstly, we leverage published 16S rRNA gene sequence datasets to determine the species-level distributions of Bacteroides members in reptile hosts. Secondly, we mine publicly available metagenomes to extract data for Bacteroides from reptiles, birds, amphibians and mammals, to compare the functional potential of Bacteroides in different host taxa. The 16S rRNA gene analyses revealed that B. acidifaciens is the most common Bacteroides species in reptile guts, and that different orders of reptiles differ in which Bacteroides species they harbour. The taxonomy of Bacteroides species recovered from metagenomic assembly did not differ between reptile orders or substantially across birds, amphibians and mammals. Metagenome-assembled genomes for Bacteroides species were marginally more related when their hosts were more closely related, with reptile hosts in particular harbouring markedly more unique Bacteroides MAGs compared to other hosts. Our findings indicate that hosts harbour similar profiles of Bacteroides species across broad comparisons, but with some differences between reptile groups, and that Bacteroides appears to perform largely similar roles in vertebrate host guts regardless of host relatedness.

Pharmacokinetic characteristics of florfenicol in green sea turtles (Chelonia mydas) and hawksbill sea turtles (Eretmochelys imbricata) after intramuscular administration

The pharmacokinetics of florfenicol (FFC) in green sea and hawksbill sea turtles were evaluated following intramuscular (i.m.) administration at two different dosages of 20 or 30 mg/kg body weight (b.w.). This study (longitudinal design) used 5 green sea and 5 hawksbill sea turtles for the two dosages. Blood samples were collected at assigned times up to 168 h. FFC plasma samples were analyzed using validated high-performance liquid chromatography equipped with diode array detection. The pharmacokinetic analysis was performed using a non-compartment approach. The FFC plasma concentrations increased with the dosage. The elimination half-life was similar between the treatment groups (range 19-25 h), as well as the plasma protein binding (range 18.59%-20.65%). According to the surrogate PK/PD parameter (T > MIC, 2 μg/mL), the 20 and 30 mg/kg dosing rates should be effective doses for susceptible bacterial infections in green sea and hawksbill sea turtles.