Immune challenges increase network centrality in a queenless ant

Abstract

Social animals display a wide range of behavioural defences against infectious diseases, some of which increase social contacts with infectious individuals (e.g. mutual grooming), while others decrease them (e.g. social exclusion). These defences often rely on the detection of infectious individuals, but this can be achieved in several ways that are difficult to differentiate. Here, we combine non-pathogenic immune challenges with automated tracking in colonies of the clonal raider ant to ask whether ants can detect the immune status of their social partners and to quantify their behavioural responses to this perceived infection risk. We first show that a key behavioural response elicited by live pathogens (allogrooming) can be qualitatively recapitulated by immune challenges alone. Automated scoring of interactions between all colony members reveals that this behavioural response increases the network centrality of immune-challenged individuals through a general increase in physical contacts. These results show that ants can detect the immune status of their nest-mates and respond with a general ‘caring’ strategy, rather than avoidance, towards social partners that are perceived to be infectious. Finally, we find no evidence that changes in cuticular hydrocarbon profiles drive these behavioural effects.

Immune Stimulation via Wounding Alters Chemical Profiles of Adult Tribolium castaneum

“…The CHC profiles of immune-stimulated beetles in the present study, especially the wounded ones, were characterized by higher proportions of shorter methyl-branched alkanes. This is in line with studies on other insect species, in which specifically methyl alkane CHCs were altered by immune challenge (Richard et al 2008; Baracchi et al 2012; Alciatore et al 2021), and could therefore contribute to social transfer of immunity. Despite higher metabolic costs for these CHCs (Nelson 1993), a generally more important role of methyl alkanes in comparison to linear n -alkanes as interspecific recognition cues is well documented in social insects (van Zweden and d’Ettorre 2010).…”

“…They serve as pheromones or allelochemicals for recognition of species, sex, mutualistic partners, or hosts, and for nestmate recognition and regulation of social interactions in eusocial insects (van Zweden and d’Ettorre 2010; Leonhardt et al 2016). Many behavioral reactions to immunological and disease cues of nestmates in social insects, and even in a non-social insect species, could be directly related to changes in CHC profiles (Richard et al 2008; Nielsen and Holman 2012; Baracchi et al 2012; Hernández López et al 2017; Alciatore et al 2021). However, in an ant species immune experiences resulted in changes in the CHCs, but their role in the observed nestmate responses were unclear, suggesting volatile chemicals or behavioral cues as mediators (Alciatore et al 2021).…”

“…Many behavioral reactions to immunological and disease cues of nestmates in social insects, and even in a non-social insect species, could be directly related to changes in CHC profiles (Richard et al 2008; Nielsen and Holman 2012; Baracchi et al 2012; Hernández López et al 2017; Alciatore et al 2021). However, in an ant species immune experiences resulted in changes in the CHCs, but their role in the observed nestmate responses were unclear, suggesting volatile chemicals or behavioral cues as mediators (Alciatore et al 2021). These findings underline that different infochemicals can be involved in information transfer among conspecifics (Müller et al 2020).…”

Rescue Strategy in a Termite: Workers Exposed to a Fungal Pathogen Are Reintegrated Into the Colony

“…This strong detection ability allows social insects to adjust their behavior to reduce disease transmission risk. In several species of ants and bees, infected and contagious individuals self-isolate themselves, either by reducing their contact with nestmates or by leaving the nest entirely (Walker and Hughes, 2009;Chapuisat, 2010;Heinze and Walter, 2010;Bos et al, 2012;Stroeymeyt et al, 2018;Geffre et al, 2020;Alciatore et al, 2021).…”

Emergent regulation of ant foraging frequency through a computationally inexpensive forager movement rule

“…Accordingly, it may be that nest architecture will affect the sampling characteristics of the foragers, and consequently their foraging frequency ( [50], [51]). Other factors that may affect the forager's sample include the number of nest entrances ( [52], [53]), the density of ants in the nest, and the topology of the colony's trophallactic network ( [9], [14]- [17], [54]- [57]). Fortunately, modern tracking methods enable to acquire more data on trophallactic networks to explore these potential effects ( [28], [58]).…”