Termites shape their collective behavioural response based on stage of infection

Abstract

Social insects employ a range of behaviours to protect their colonies against disease, but little is known about how such collective behaviours are orchestrated. This is especially true for the social Blattodea (termites). We developed an experimental approach that allowed us to explore how the social response to disease is co-ordinated by multistep host-pathogen interactions. We infected the eastern subterranean termite Reticulitermes flavipes with the entomopathogenic fungus Metarhizium anisopliae, and then, at different stages of infection, reintroduced them to healthy nestmates and recorded behavioural responses. As expected, termites groomed pathogen-exposed individuals significantly more than controls; however, grooming was significantly elevated after fungal germination than before, demonstrating the importance of fungal status to hygienic behaviour. Significantly, we found that cannibalism became prevalent only after exposed termites became visibly ill, highlighting the importance of host condition as a cue for social hygienic behaviour. Our study reveals the presence of a coordinated social response to disease that depends on stage of infection. Specifically, we show how the host may play a key role in triggering its own sacrifice. Sacrificial self-flagging has been observed in other social insects: our results demonstrate that termites have independently evolved to both recognize and destructively respond to sickness.

Dissecting the genetic architecture of a stepwise infection process

“…holds the key to resolving the genetic architecture of the entire defence cascade and consolidate our understanding for how different defence components evolve (see also Davis, Meconcelli, Radek, & McMahon, 2018;Duneau et al, 2017;Lievens et al, 2018). In this study, we dissect the genetic architecture of a stepwise infection process using a bacterial pathogen of the water-flea Daphnia magna;…”

Inhibition of a Secreted Immune Molecule Interferes With Termite Social Immunity

“…The Petri dish nest was built as described elsewhere (Davis et al, 2018) to house experimental mini-colonies of R. flavipes. The petri dish experimental nest (94 × 16 mm) contained two cellulose pads (45.5 mm diameter, 0.9 mm thick) (Pall) which were placed on top of the two thin filter paper disc Whatman No.…”

“…However, understanding when and why different collective defenses are deployed in response to an infectious disease threat remains a significant challenge to research. We recently showed that termites can employ a range of collective responses depending on the individual's progression along the stepwise-infection process (Davis et al, 2018). But we do not understand the underlying mechanism(s) responsible for regulating the point at which these different responses are deployed.…”

“…As facultative pathogens, they are widespread in the environment surrounding insect colonies (Cremer et al, 2018). We selected M. anisopliae for use in our experiments as it is a natural pathogen of termites including Reticulitermes flavipes (Zoberi, 1995;Dong et al, 2007) and has served as an effective model entomopathogen in the study of virulence and termite immune defense (Chouvenc et al, 2009;Chouvenc and Su, 2010;Hamilton and Bulmer, 2012;Davis et al, 2018).…”

Defences against brood parasites from a social immunity perspective

“…Instead, the donor has to rely on visual or chemical signatures of infection being displayed by the infected individual, e.g. ants [72 -74] and termite [75], or even active transfer of information on infection status by the recipient, e.g. warning dances in termites [76,77].…”