Fish skin microbiomes shift dramatically as species transition from aquatic to terrestrial habitats
A new study characterizes the skin microbiomes of three combtooth blenny fish species occupying progressively more terrestrial habitats along Guam's intertidal zone, finding that microbiome composition closely mirrors each species' habitat. The most terrestrially adapted species showed the most divergent microbial community, enriched with land-associated bacterial taxa. The findings suggest microbial symbionts may play an active role in enabling fish to adapt to amphibious and terrestrial lifestyles.
Researchers used 16S rRNA amplicon sequencing to compare skin-associated bacterial communities in three combtooth blenny species — Blenniella paula (subtidal/aquatic), Praealticus labrovittatus (intertidal/amphibious), and Alticus arnoldorum (supratidal/terrestrial) — along with surrounding seawater and substrate biofilms in Guam. Skin microbiomes were consistently distinct from environmental microbial communities, indicating that the host fish actively filter and shape their own microbial assemblages rather than simply reflecting ambient conditions. The degree of divergence between skin and substrate microbiomes increased in parallel with each species' position higher on the intertidal gradient. The supratidal species A. arnoldorum showed the most distinctive microbiome, marked by elevated Gammaproteobacteria and enrichment of epiphytic and mucus-associated taxa not typically found in aquatic marine fish. Across all three species, 32 microbial orders were significantly enriched on the skin relative to environmental samples, including both common fish-mucosa taxa such as Vibrio and Alteromonas, and rarer groups like Rubritalea and Granulosicoccus. The authors propose this is the first comparative study of skin microbiome divergence across amphibious fish along an intertidal gradient, and suggest the framework could help predict how microbiomes respond to broader environmental change.
What's missing
The study is a preprint posted to bioRxiv and has not yet undergone peer review, so findings should be interpreted with caution. The authors do not establish causality — it remains unclear whether microbiome differences drive habitat adaptation or are simply a consequence of environmental exposure. Functional roles of the enriched microbial taxa in host physiology are inferred but not experimentally tested.
What different sources said
- bioRxivCenter
Phylogenetic coherence in microbiome composition across environmental gradients
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