Microbial transfer through fecal strings on eggs affects leaf beetle microbiome dynamics

Area of Science:

• Insect microbiology
• Microbial ecology
• Evolutionary biology

Background:

• Metamorphosis significantly impacts insect gut microbiomes.
• Specialized transmission routes are crucial for microbiome colonization between host life stages.
• The genus *Galerucella* exhibits varying maternal fecal string deposition behaviors on eggs.

Purpose of the Study:

• To investigate how different microbial transfer mechanisms affect gut microbial community dynamics across insect life stages.
• To compare gut microbiome stability in *Galerucella* species with and without fecal string deposition.
• To understand the role of maternal provisioning in insect gut microbiome establishment.

Main Methods:

• 16S rRNA gene amplicon sequencing was used to analyze gut microbial communities.
• Comparative analysis of gut microbial communities across larval, pupal, and adult stages.
• Five *Galerucella* species, differing in fecal string behavior, were studied.

Main Results:

• Gut microbiome alpha-diversity was more stable across life stages in species that deposit fecal strings.
• Consistent interspecific microbiome differences were observed, with several taxa present across all life stages.
• Fecal string deposition appears to facilitate stable vertical transfer of gut bacteria.

Conclusions:

• Maternal fecal strings play a key role in maintaining gut bacterial diversity and dynamics in *Galerucella*.
• Fecal string deposition enhances the vertical transmission of gut microbes between insect generations.
• Non-fecal string-placer species rely on alternative, less efficient transmission routes for microbiome establishment.