Fast acquisition of a polysaccharide fermenting gut microbiome by juvenile green turtles Chelonia mydas after settlement in coastal habitats

Abstract

BackgroundTetrapods do not express hydrolases for cellulose and hemicellulose assimilation, and hence, the independent acquisition of herbivory required the establishment of new endosymbiotic relationships between tetrapods and microbes. Green turtles (Chelonia mydas) are one of the three groups of marine tetrapods with an herbivorous diet and which acquire it after several years consuming pelagic animals. We characterized the microbiota present in the feces and rectum of 24 young wild and captive green turtles from the coastal waters of Brazil, with curved carapace length ranging from 31.1 to 64.7 cm, to test the hypotheses that (1) the ontogenetic dietary shift after settlement is followed by a gradual change in the composition and diversity of the gut microbiome, (2) differences exist between the composition and diversity of the gut microbiome of green turtles from tropical and subtropical regions, and (3) the consumption of omnivorous diets modifies the gut microbiota of green turtles.ResultsA genomic library of 2,186,596 valid bacterial 16S rRNA reads was obtained and these sequences were grouped into 6321 different operational taxonomic units (at 97% sequence homology cutoff). The results indicated that most of the juvenile green turtles less than 45 cm of curved carapace length exhibited a fecal microbiota co-dominated by representatives of the phyla Bacteroidetes and Firmicutes and high levels of Clostridiaceae, Prophyromonas, Ruminococaceae, and Lachnospiraceae within the latter phylum. Furthermore, this was the only microbiota profile found in wild green turtles > 45 cm CCL and in most of the captive green turtles of any size feeding on a macroalgae/fish mixed diet. Nevertheless, microbial diversity increased with turtle size and was higher in turtles from tropical than from subtropical regions.ConclusionsThese results indicate that juvenile green turtles from the coastal waters of Brazil had the same general microbiota, regardless of body size and origin, and suggest a fast acquisition of a polysaccharide fermenting gut microbiota by juvenile green turtles after settlement into coastal habitats.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0454-z) contains supplementary material, which is available to authorized users.

The effect of diet on the gastrointestinal microbiome of juvenile rehabilitating green turtles (Chelonia mydas)

“…This is a common assumption in the literature, although variation in community composition has been demonstrated among gastrointestinal sampling sites in horses, another hindgut fermenter [30]. In sea turtles, the most common sample types are feces and cloacal swabs; thus our results are comparable to other studies [10][11][12][13]. Our results show that regardless of diet, the fecal bacterial phyla of green turtles consists primarily of Firmicutes and Bacteroidetes, a feature that appears to be conserved across many vertebrate taxa, including other marine herbivores and green turtles elsewhere [11,13,[31][32][33][34].…”

“…Rarefaction curves showing alpha diversity indices (Chao1, Shannon and Observed OTUs) and beta-diversity analysis using principal coordinate analysis (PCoA) plots and weighted and unweighted UniFrac distance metrics were generated within QIIME 1.9 [28]. QIIME 1.9 has recently been replaced by QIIME 2.0, however the authors do not feel that analysis using QIIME 1.9 reduces the reliability of the conclusions drawn in this study, and allows comparison to other studies using similar versions of the program [12,13].…”

“…Despite considerable advancements in the study of the GI microbiota and a seemingly exponential increase in the number of studies in various taxa of animals, the reptilian microbiome remains poorly understood [8]. Knowledge about the microbiome of sea turtles, all species of which are listed internationally as either Threatened or Endangered [9], is limited but expanding [10][11][12][13][14][15][16]. Understanding endangered sea turtle core microbiota and what influences its composition is likely to influence how we manage conservation efforts.…”

Household Pet Ownership and the Microbial Diversity of the Human Gut Microbiota

“…OTU 784, Akkermansia, was not present when only assessing the microbiome of cat and dog owners, though this genera has previously been identified in rodents (Nagpal et al, 2018) and reptiles (Campos et al, 2018). Akkermansia was the only differentially abundant OTU we were able to tentatively to the species level.…”

Green turtle diet is dominated by seagrass in the Western Indian Ocean except amongst gravid females

“…Food selection may correlate with differences in intestinal microflora (Bjorndal 1980), which varies as turtles transition from pelagic to neritic habitats (Campos et al 2018;Price 2016) and with state of health (Ahasan et al 2017). It follows that intestinal microflora typical of individuals that feed on seagrass likely differs from that of algivores and they are less efficient at digesting algae and vice versa (Bjorndal et al 1991), but diets comprising large amounts of both seagrass and algae are also sometimes reported (e.g., López-Mendilaharsu et al 2005;Shimada et al 2014;Whiting et al 2014).…”