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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - DISEASE (Disease Risk And Immune Strategies In Social Insects)

Teaser

Summary

Group-living has been predicted to have opposing effects on disease risk and immune strategies. First, since repeated contacts between individuals facilitate pathogen transmission, sociality may favour high investment in personal immunity. Alternatively, because social animals can limit disease spread through collective sanitary actions (e.g., mutual grooming) or organisational features (e.g., division of the groupâ€™s social network into distinct subsets), sociality may instead favour low investment in personal immunity. The overall goal of this project is to experimentally test these conflicting predictions in ants using advanced data collection and analytical tools. I will first quantify the effect of social organisation on disease transmission using a combination of automated behavioural tracking, social network analysis, and empirical tracking of transmission markers (fluorescent beads). Experimental network manipulations and controlled disease seeding by a robotic ant will allow key predictions from network epidemiology to be tested, with broad implications for disease management strategies. I will then study the effect of colony size on social network structure and disease transmission, and how this in turn affects investment in personal immunity. This will shed light on far-reaching hypotheses about the effect of group size on social organisation (\'size-complexityâ€™ hypothesis) and immune investment (â€˜density-dependent prophylaxisâ€™). Finally, I will explore whether prolonged pathogen pressure induces colonies to reinforce the transmission-inhibiting aspects of their social organisation (e.g., colony fragmentation) or to invest more in personal immunity. This project will represent the first empirical investigation of the role of social organisation in disease risk management, and allow its importance to be compared with other immune strategies. It will significantly advance our understanding of the complex feedback between sociality and health, and uncover the antsâ€™ optimal investment in disease defences depending on colony size, social complexity, and disease pressure.

Work performed

During the first five months of the project, I have focused on (i) ordering all material and equipment necessary to build the 10 automated tracking systems for ants, (ii) selecting team members, (iii) collecting the ant colonies necessary for the first year of the project, and (iv) establishing the collaborations necessary for the implementation of the project. I have made significant progress in building the tracking systems - this task will be finished by the end of month 7 of the action. I have selected two PhD students and one post-doc, who will join me at my host Institution between months 6-11 of the action. I have collected 300 Lasius niger queens which have successfully started new colonies. I have successfully obtained all relevant information from Prof Thomas Flatt regarding methods to extract the hemolymph of single insects in view of analysing the immune investment of isolated individuals, and I have initiated a long-lasting collaboration with Prof Bruno Lemaitre (EPFL) to characterize the immune system of Lasius niger ants.

Final results

In spite of the change in Host institution 5 months after the beginning of the action, we have started the work on Aim 2 (effects of colony size on disease transmission risk) early, and we are on good track to keep to schedule so far. We expect to have collected and analysed all data related to the growth of unmanipulated colonies by the end of year 1 of the action.