Behavioral and microbial ecology in colonies of Atta sexdens (Hymenoptera: Formicidae): modeling defensive microbial responses

• Ano de defesa: 2025
• Autor(a) principal: Bueno, Isabella
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Entomopathogenic fungi; Formiga-cortadeira; Fungos entomopatogênicos; Imunidade social; Leaf-cutter ant; Simbiose; Social immunity; Symbiosis
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/11/11146/tde-04112025-122907/

Social immunity represents a key adaptation in eusocial insects, enabling collective protection against infections in densely populated environments with frequent social interactions. This research examines the behavioral and microbial ecology of Atta sexdens, focusing on the interactions among workers, symbionts, and pathogens. Chapter 1 provides a general introduction, outlining the significance of social immunity and defensive strategies in leaf-cutting ants. Chapter 2 explores the physiological and behavioral responses of workers to different fungal pathogens. Analyses of metapleural gland secretions revealed pathogen-specific variation, while behavioral observations showed distinct defensive responses specific to each challenge, suggesting the existence of complementary and adaptive strategies. In vitro assays confirmed the antifungal activity of the glandular secretions. Chapter 3 combines experimental data and mathematical modeling to assess the role of grooming in regulating ant and fungal symbiont biomass under entomopathogenic infection. Results indicate that although self-grooming plays a critical role in mitigating the effects of Metarhizium anisopliae, the pathogen still causes a significant reduction in colony biomass, even under optimal behavioral defense. The multicameral architecture of the colonies was shown to redistribute biomass and delay population collapse. In Chapter 4, Markov models were applied to characterize the dynamics of prophylactic behaviors, revealing that the presence of pathogens, fungal garden, and brood increases the frequency of specific forms of grooming. These findings highlight behavioral plasticity in response to environmental and social cues. Chapter 5 investigates how repeated fungal challenges influence social contact networks in mini-colonies. Successive exposures led to subtle reorganizations in social structure, including a reduction in the density of tightly connected subgroups. Finally, Chapter 6 evaluates the effects of homologous and heterologous pathogen exposures on mortality in experimental colonies. Repeated exposures to the same pathogen resulted in a significant decrease in mortality, consistent with the presence of social immune memory, whereas exposures to different pathogen species did not produce a comparable protective effect.