Symbiotic Bacteria in Juncos Scents

In recent decades it has become increasingly clear that complex animals are hosts to hordes of microorganisms, many of which are crucial symbiotes that contribute to the health and success of the animal.  The more we learn, the more we animals look like the infrastructure for societies of microbes.

This fall researchers from several Universities report on a fascinating study of microbes that live in common songbirds, the dark-eyed junco (Junco hyemalis) [1].  The particular bacteria studied live in the scent glands of the birds, and could be involved in producing chemical signals, i.e., smells.

The investigation examined the role of these bacteria in the life of the birds. Of particular interest are the components of “preen oil”, which include volatile compound (i.e., scents).  Some of these compounds sharply increase during mating times, and “most likely to play a role in sexual signalling and mating behaviour” (p. 2 )  (See the paper for details of the specific biochemicals involved.)

When the birds were treated with antibiotics which they showed killed the symbiotes.  This treatment also decreased a group of volatile compounds which have been connected to reproductive success.

Further study cultured bacteria extracted from preen oil, and found these compounds. I.e., these bacteria generate these important (to Juncos) compounds.

In short, the study suggests that the symbiotic bacteria produce compounds that are a critical part of Junco breeding behavior.  No bugs, no Juncos.

Assuming this study is validated by future work, there are interesting questions to answer.  How do these bacteria interact with the bird, e.g., to trigger the odors during mating season?  How are these strains passed down to descendants?  How are they shared within populations?  Are they shared across populations?

And, of course, it is interesting to wonder how this symbiosis coevolved over time.

  1. Danielle J. Whittaker, Samuel P. Slowinski, Jonathan M. Greenberg, Osama Alian, Andrew D. Winters, Madison M. Ahmad, Mikayla J. E. Burrell, Helena A. Soini, Milos V. Novotny, Ellen D. Ketterson, and Kevin R. Theis, Experimental evidence that symbiotic bacteria produce chemical cues in a songbird. The Journal of Experimental Biology, 222 (20):jeb202978, 2019.


PS.  Some good names for a band:

Preen Oil (and Carolina Preen Oil)
Carolina Junco
Dark eyed Junco


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