Symbiotic relationships between host and microbiome can play a major role in local adaptation. Previous studies with freshwater organisms have shown that microbiome performs numerous important biochemical functions for the host, playing a key role in metabolism, physiology or health. Experimental studies in fish groups have found an effect of enzymatic activity of gut microbiota on a variety of metabolic processes. The goal of this 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. 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. Therefore, and unexpectedly, the microbiota of A. mexicanus is not linked with the contrasting conditions of the habitat considered here but is related to water parameters.

Symbiotic relationships between host and microbiome can play a major role in local adaptation. Previous studies with freshwater organisms have shown that microbiome performs numerous important biochemical functions for the host, playing a key role in metabolism, physiology or health. Experimental studies in fish groups have found an effect of enzymatic activity of gut microbiota on a variety of metabolic processes. The goal of this study was to compare stomach microbiome from cave and surface Astyanax mexicanus, in order to evaluate the potential response of microbiota to locally contrasting environmental conditions and physiological adaptations of the host. Stomach biopsies were 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 Betaprotobacteria were the most abundant phyla across the samples. 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 (caves vs surface rivers). Rather, we observed a consistent association between β-diversity and dissolved oxygen concentration in water. Therefore, and unexpectedly, the microbiota of A. mexicanus is not linked with the habitat but results from water conditions.

Here, we present the mitogenome of the blood feeding leech Haementeria acuecueyetzin (Hirudinida: Glossiphoniidae) based on specimens collected in Tabasco, Mexico. The circular genome is 14,985 bp in length, and consists of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and an AT-rich control region. Phylogenetic analysis based on the 13 protein-coding genes and two rRNA genes places H. acuecueyetzin sister to H. officinalis within the family Glossiphoniidae. Mitochondrial gene order in H. acuecueyetzin is consistent with other members of Clitellata with no evidence of gene gain/loss, duplication, or rearrangement.

Symbiotic relationships between host and microbiome can play a major role in local adaptation. Previous studies with freshwater organisms have shown that microbiome performs numerous important biochemical functions for the host, playing a key role in metabolism, physiology or health. Experimental studies in fish groups have found an effect of enzymatic activity of gut microbiota on a variety of metabolic processes. The goal of this study was to compare stomach microbiome from cave and surface Astyanax mexicanus, in order to evaluate the potential response of microbiota to locally contrasting environmental conditions and physiological adaptations of the host. Stomach biopsies were 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 Betaprotobacteria were the most abundant phyla across the samples. 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 (caves vs surface rivers). Rather, we observed a consistent association between β-diversity and dissolved oxygen concentration in water. Therefore, and unexpectedly, the microbiota of A. mexicanus is not linked with the habitat but results from water conditions. 28 and V9. A high diversity was observed across samples, including 16 phyla, 120 families and 178 29 genera. Gammaproteobacteria, Firmicutes, Bacteroidetes and Betaprotobacteria were the most 30 abundant phyla across the samples. Although the relative abundance of the core OTUs at genus 31 level were highly contrasting among populations, we did not recover differences in stomach 32 microbiome between contrasting habitats (caves vs surface rivers). Rather, we observed a 33 consistent association between β-diversity and dissolved oxygen concentration in water.34 Therefore, and unexpectedly, the microbiota of A. mexicanus is not linked with the habitat but 35 results from water conditions. 36 37