The Advantageous Microbiome of a Celebrity Cichlid

Access to resources enjoyed by dominant animals within a social hierarchy leads to distinct behavioural and physiological changes. This induces dynamic, population-level shifts in microbiome composition, mediated by the presence of certain bacterial clades. Singh et al. (2019) performed bioinformatic analysis of 16S rDNA sequences from faecal samples to examine if the social hierarchy in the cichlid fish, Astatotilapia burtoni, influences their gut microbiome. At high social rank, gut microbial diversity and the abundance of beneficial microbial clades increased, stabilizing the community by broadening available niche space. In subordinate animals, an increase in pathogen load, specifically Enterobacteriaceae, was seen, resulting in a loss of microbial community diversity.

The fish microbiome has been shown to direct the development and function of host neural, endocrine and immune systems and is considered vital to maintaining host physiological and metabolic homeostasis, highlighting the importance to integrate microbiome derived physiological effects into future studies of behaviour. In this study, the OTU number was lower than those in similar studies that directly sampled gut tissue, indicating that non-invasive faecal samples cannot provide a complete synopsis of gut microbiota. This may explain why Firmicutesand Verrucomicrobia were absent here, yet found to be part of the core gut microbiome in similar cichlid studies.

Singh, A., Hammond, J. J. F., O'Rourke, C. F., & Renn, S. C. (2019). Gut microbial diversity increases with social rank in the African cichlid fish, Astatotilapia burtoni. Animal Behaviour, 152, 79-91. This article can be found at: https://www.sciencedirect.com/science/article/pii/S0003347219301125