Effects of Prolonged Fasting on Cloacal Microbiota of Crotalus durissus with Different Corporal Scores

Aims: This study provides a detailed analysis of the composition and diversity of the bacterial community within the cloacal cavity of Crotalus durissus (Cascavel) under the influence of diet and the corporal score of breeding snakes through metagenomics analysis. For this aim, the study also provides a body condition score protocol for the classification of snakes as thin, normal, and obese.

Study Design: The experimental groups were established from snake body conditions such as visibility of ribs, the aspect of the side view, the upper and ventral view, and the aspect of the final portion, of the neck and square bone.

Place and Duration of Study: The research was conducted at S-Inova Laboratory at Don Bosco Catholic University, between December 2017 and February 2019 (Mato Grosso do Sul, Brazil).

Methodology: There are 3 groups of score corporations: thin (n=3), normal (n=3), and obese (n=3). The first sample of each animal was obtained 7 days after feeding and the second sample after 50 days of fasting. The metagenomic DNA was extracted from all 18 swab samples through DNeasy® PowerSoil® Kit (Qiagen). Thereafter the samples were submitted to sequencing, performed using the 2 x 250bp paired-end sequencing on a single run of an Illumina HiSeq, followed by the application of bioinformatics tools.

Results: The most representative phyllo for all the samples was Proteobacteria (69,4%), followed by Bacteroidetes (19,2%) and Synergists (11,2%). In the group of obese snakes, the phylum Proteobacteria still being the group with the higher relative abundance in the two moments, with a decrease of 9,6%, as well as the phylum Bacteroidetes which decreased by 5,5% in the second moment (after fasting). Differently, the groups of the normal and thin have a decrease of 37,2% and 29,4% respectively of the phylum Proteobacteria and an increase of the relative abundance of 35% and 27,9% of the phylum Bacteroidetes. Before prolonged fasting the groups obtained 213 shared OTUs which reduced to 206 after the prolonged fasting, suggesting that, in general, the treatment influences microbial communities of the groups, which was possible to observe when analyzed and compared individually. The index of Shannon diversity showed that before the fasting, the groups of obese snakes and normal presented a bigger richness of species, differently from the thin group that showed more diversity after 50 days of fasting. The variance analysis showed that the obese snakes presented a bigger proximity to the samples collected before the prolonged fasting. The samples showed greater proximity in PCA analyses and ANOVA when considering the prolonged fasting time than when compared by body score.

Conclusion: With this study, it was possible to conclude that prolonged fasting can influence the cloacal microbiota of the snake Crotalus durissus, except in the individuals considered obese.