Date of Completion


Embargo Period



Hirudo verbana, Macrobdella decora, leech, microbiome, juvenile, transmission

Major Advisor

Joerg Graf

Associate Advisor

Daniel Gage

Associate Advisor

Spencer Nyholm

Associate Advisor

Jonathan Klassen

Associate Advisor

Victoria Robinson

Field of Study



Doctor of Philosophy

Open Access

Open Access


The medicinal leech is a developing experimental model of gut symbioses. Aeromonas veronii and Mucinivorans hirudinis are core members of the gut microbial community in Hirudo verbana and may aid the leech in digesting the blood meal, preserving the blood meal, and keeping invading bacteria from colonizing the gut. The bladders of H. verbana contain an entirely different microbial consortium. The scientific interest in this symbiosis is currently due to its simple nature and the extreme dietary habits of the leech. In order to increase the usefulness of this model, a more sophisticated understanding of processes by which the microbiome is acquired and develops is necessary. In my dissertation I have compared the gut and bladder microbiomes of H. verbana to that of M. decora (the North American medicinal leech) in order to determine the conservation of symbionts. I have additionally examined the potential for horizontal and vertical transmission of gut and bladder symbionts to hatchling and juvenile H. verbana. With such information, future researchers will be able to draw parallels between processes occurring in the leech to those occurring in other organisms. A more detailed understanding of processes conserved or lost between symbiotic partners will lead to a better understanding of processes required for colonization and persistence across a wide range of animals.