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

Abstract

Social insect colonies are characterized by an efficient division of labor, allowing high-value individuals (i.e., reproductives and brood) to be sheltered from tasks associated with increased risk of pathogen exposure, such as foraging or corpse disposal. This social organization helps limit the transmission of disease throughout the colony. Further, individuals can actively respond to imminent disease threats by altering their behaviors as a means of social immunity. In subterranean termites, although workers typically avoid detected pathogens, they can be attracted to pathogen cues when a nestmate is infected. Infected termites are usually groomed, but they may instead be cannibalized if the infection has already become lethal. The mechanisms governing these changes in behavior are unclear. We set out to examine immediate changes in individual behaviors, investigating the role that the infected individual plays in communicating its infection status to nestmates. We also assessed gradual changes in social organization after the re-introduction of an infected termite to the colony. Our results reveal that infected termites likely do not signal their infection status to nestmates through shaking behaviors and reduced movements, suggesting the occurrence of other mechanisms used in communicating infection. We also found that infected termites do not self-isolate and may travel to the densest part of the colony, where they can potentially benefit from grooming by large groups of nestmates. These results provide new insights into how individual changes in immune behaviors contribute to overall colony health, highlighting that, at early stages of infection, termites favor a rescuing strategy rather than isolation and/or cannibalization.

Different strategies between queens and workers against fungal pathogens in the termite Reticulitermes chinensis

“…In our study, we found that termite workers groomed infected queens more intensely than infected workers after the workers and queens were simultaneously infected. This is consistent with queens having a higher value to workers than other workers, which might make workers more expendable to other colony members (Moran et al, 2022).…”

“…Typically, sterile castes responsible for such tasks have limited or no contact with the queen (and king in termites) and the larval brood (Guo et al, 2020; Stroeymeyt et al, 2018), even to the point of pathogen‐infected individuals self‐isolating from the colony (Geffre et al, 2020; Heinze & Walter, 2010). However, some pathogen‐infected nonreproductive termites do not self‐isolate and may still move in and out of all parts of the colony, where they can potentially benefit from being groomed by other nestmates (Moran et al, 2022). However, this also poses a potential infection risk to the queen.…”

Overcoming Immune Deficiency with Allogrooming

“…LOMs are positively correlated with R. flavipes worker aggregation and allogrooming [ 23 ], which suggests that individuals exhibiting alarm in this study solicited more grooming from nestmates. LOMs are rarely reported in research investigating Metarhizium infections in termites and have been discounted as playing a role in signaling pathogen exposure [ 30 ]. However, they may be missed because they do not occur in isolated individuals, are not substantially elicited by certain strains and species of Metarhizium , take approximately 3 min after a challenge before they escalate, and subside after approximately 30 min [ 22 , 23 ].…”

Cross-talk between immunity and behavior: insights from entomopathogenic fungi and their insect hosts

“…M. ruba infected by M. anisopliae ) (Leclerc and Detrain 2016 ). Reticulitermes flavipes termite workers can even be reintegrated into a colony after infection with Metarhizium fungi (Moran et al 2022 ). Founding queens of the ant Formica selysi appear attracted to soil “contaminated” with Beauveria or Metarhizium (Bruetsch et al 2014 ).…”