Gut microbial ecology of nestling House Sparrows (Passer domesticus)

KOHL, KEVIN D.; ANTONIO BRUN; CAVIEDES-VIDAL E; KARASOV WH

San Francisco, CA

Congreso; SICB Annual Meeting; 2018

Society for Integrative and Comparative Biology

Recently, there has been a great deal of attention focused on the rolethat symbiotic bacteria play in the development, ecology, andevolution of hosts. Avian altricial nestlings represent an interestingstudy system in which to investigate these interactions, given thatthey exhibit the fastest growth rates among vertebrates, and growth islimited by their digestive capacity. We used 16S rRNA sequencing toinventory microbial communities in several experiments testingvarious questions. 1) How do microbial communities develop in thewild? 2) How responsive are gut microbes to dietary changes? 3)Does hosting microbes incur a cost to developing nestlings? Whensampling nestlings from the wild, we found that aspects of bacterialcommunity membership and structure changed significantly over thenestling period. The relative abundance of Proteobacteria decreasedaround day 9, while the relative abundance of Firmicutes increased.When we conducted feeding trials in captivity, we found that themicrobial communities were altered within 6 hours of a diet shift.Last, we treated some nestlings with antibiotics. Antibiotic treatmentsignificantly increased growth and food conversion efficiency innestlings. Antibiotics did not alter aspects of gut anatomy, butdepressed intestinal maltase activity. Thus, we conclude thatmicrobial-induced growth limitation in developing birds is not drivenby interactions with digestive capacity, but may be driven bydecreased energetic costs of immune function or beneficial effectsfrom microbes enriched under antibiotic treatment. Overall, thesestudies demonstrate that the digestive system and gut microbiota ofdeveloping House Sparrows respond rapidly to changes in diet.