Zebrafish ( <i>Danio rerio</i> ) behavioral phenotypes are not underscored by different gut microbiomes

Although bold and shy behavioral phenotypes in zebrafish (<i>Danio rerio</i>) have been selectively bred and maintained over multiple generations, it is unclear if they are underscored by different gut microbiota. Using the microbiota-gut-brain concept, we examined the relationship between gut microbiota and the behavioral phenotypes within this model animal system to assess possible gut microbe-mediated effects on host behavior. To this end, we amplified and sequenced 16S rRNA gene amplicons from the guts of bold and shy zebrafish individuals using the Illumina Miseq platform. We did not record any significant differences in within-group microbial diversity nor between-group community composition of the two behavioral phenotypes. Interestingly, though not statistically different, we determined that the gut microbial community of the bold phenotype was dominated by <i>Burkholderiaceae</i>, <i>Micropepsaceae</i>, and <i>Propionibacteriaceae</i>. In contrast, the shy phenotype was dominated by <i>Beijerinckaceae</i>, <i>Pirelullacaeae</i>, <i>Rhizobiales_Incertis_Sedis</i>, and <i>Rubinishaeraceae</i>. The absence of any significant difference in gut microbiome profiles between the two phenotypes would suggest that in this species, there might exist a stable core gut microbiome, regardless of behavioral phenotypes, and possibly, a limited role for the gut microbiota in modulating this selected-for host behavior. This study characterized the gut microbiomes of distinct innate behavioral phenotypes of the zebrafish (that are not considered dysbiotic states) and did not rely on antibiotic or probiotic treatments to induce changes in behavior. Such studies are crucial to our understanding of the modulating impacts of the gut microbiome on normative animal behavior.