Symbiotic relationships between host and microbiome can play a major role in local adaptation.
In this respect, gut microbiome performs numerous important biochemical functions for the host,
playing a key role in metabolism, physiology or health. Astyanax mexicanus species, which
presents an extraordinary capability adapt to contrasting conditions, giving us a unique
opportunity to explore the role of gut microbiome in the adaption to extreme conditions, as the
ones in the caves. Thus, the goal of our study was to compare stomach microbiome from cave
and surface Astyanax mexicanus, in order to evaluate the potential response of microbiota to
contrasting environmental conditions and physiological adaptations of the host. Stomach
microbiota was obtained from three different populations: Pachón cave, and two surface rivers
(Rascón and Micos rivers). The stomach microbiome was analyzed using the Ion 16S
Metagenomic kit considering seven variable regions: V2, V3, V4, V6-7, V8 and V9. A high diversity
was observed across samples, including 16 phyla, 120 families and 178 genera.
Gammaproteobacteria, Firmicutes, Bacteroidetes and Betaproteobacteria were the most
abundant phyla across the samples, the abundance of this groups is concordant with other fish
gut microbiota. Although the relative abundance of the core OTUs at genus level were highly
contrasting among populations, we did not recover differences in stomach microbiome between
contrasting habitats (cave vs. surface rivers). Rather, we observed a consistent association
between β-diversity and dissolved oxygen concentration in water. Thus, microbiota of A.
mexicanus is related to water parameters, rather than contrasting habitats (i.e. troglobitic vs