Ģ��ֱ��

This thesis explores the contribution bacteria make to the defence secretions of the wood tiger moth. Bacteria were found in the defence secretions that this moth uses to slow or stop attacks by birds. Moths treated with antibiotics had their defences tested with multiple approaches. Defences from treated moths suffered faster attacks from birds. No differences were seen in the amount of important chemicals, called pyrazines. The taxonomic identification of the bacteria in the defensive secretions found hundreds of taxa. Subsequently, potential key bacterial groups and their occurrence patterns were searched for in wild wood tiger moth populations across Finland and Estonia and within a Finnish population over a four years. The bacteria in wild moth populations were consistent across Finland and Estonia within a single season. However, bacterial communities changed from year to year, leaving no obvious bacterial species which could be a permanent, functional resident in the moths.

Wood tiger moths treated with antibiotics had their gene expression and development examined to investigate how the moths reacted to bacterial depletion during their larval stages. Wood tiger moths reached adulthood significantly quicker following bacterial depletion than untreated relatives. Additionally, immune-related genes were less active in bacteria-depleted moths, while growth-related genes were highly active.

When the results are viewed together, a complicated picture of bacterial contribution, variability, and costs for the host emerges. The bacteria provide an uncharacterised functionality to the defensive secretions that slow bird attacks, but they do not impact the important pyrazines in the secretions. Overall, the bacteria present in the defensive secretions of wood tiger moths come at a cost requiring investment in the immune system, while simultaneously providing some protection benefits against bird predators.

The dissertation is published in JYU Dissertations series, number 517, Jyväskylä 2022. ISBN 978-951-39-9141-8 (PDF), URN:ISBN:978-951-39-9141-8, ISSN 2489-9003. Link to publication:

M.Sc. Liam Murphy defends his doctoral dissertation ”Defensive symbiosis of the wood tiger moth (Arctia plantaginis)” on 13 May at 15. Opponent Professor Keith Clay (Tulane University, USA) and Custos Docent Juan Galarza (Ģ��ֱ��). The doctoral dissertation is held in English.

The audience can follow the dissertation in the lecture hall or online.

Link to the Zoom Webinar event (Zoom application or Google Chrome web browser recommended):