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Simpson, M.C. (2025) Investigating the role of metapleural glands in social immunity and the role of co-founding in pathogen resistance in Messor barbarus. MRes thesis, University of Nottingham.

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Abstract

The risk of pathogen infection due to increased within-group transmission is theorised to be a major potential cost of group-living and eusociality. Many eusocial insects have evolved defence mechanisms to mitigate this risk and mount collective defences against pathogens. Social immunity describes the behaviours which are used to minimise pathogen spread within a colony, such as allo-grooming and waste management. Additionally, ants have developed chemical defences, such as the antimicrobial substance produced by the metapleural gland. This thesis investigated how the availability of metapleural glands and social immunity affect the survival probability of Messor barbarus and their response to an entomopathogenic fungus, Metarhizium brunneum. The results showed that the presence of fungal spores or Triton X on the cuticle increased self-grooming, and in the control treatment, an ant groomed for a longer period of time if they had a blocked gland. There was no difference in allo-grooming between individuals. Additionally, there was a high mortality of ants exposed to M. brunneum. More experiments are required to see whether the behaviours explored in this thesis are important or not in modulating the efficacity of the metapleural gland. There could be some other mechanism, potentially passive, involved in how the metapleural gland protects the ants from disease.

Colony-founding queens do not have access to the colony-wide defensive system, and new colonies suffer high rates of mortality. In a number of eusocial insects, queens join together and co-found a colony collectively. This thesis investigated how being exposed to M. brunneum and group type affects the founding of new colonies. The results showed that exposed single queens and unexposed previously paired queens produced the highest number of brood and adults comparatively. These findings could support a newly discovered phenomenon called “hygienic cannibalism” where a queen will reinvest nutrients back into egg production from eating infected larvae. The presence of an unrelated queen could be viewed as interacting with a foreign substance, as being exposed to either another queen or a pathogen produced a large number of brood and adults. Exposed previously paired queens had the disadvantage of both an immune response and energy lost due to fighting so produced a small number of brood and adults in comparison.

Item Type:	Thesis (University of Nottingham only) (MRes)
Supervisors:	Evison, Sophie
Keywords:	Pathogen infection; Eusocial insects; Social immunity; Metapleural gland; Ant behaviours
Subjects:	Q Science > QL Zoology > QL750 Animal behaviour Q Science > QR Microbiology > QR171 Microorganisms in the animal body
Faculties/Schools:	UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences
Item ID:	80708
Depositing User:	Simpson, Molly
Date Deposited:	24 Jul 2025 04:40
Last Modified:	24 Jul 2025 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/80708

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