Cuticular hydrocarbon cues of immune‐challenged workers elicit immune activation in honeybee queens

Abstract

Recently, evidence has shown that variations in the cuticular hydrocarbons (CHCs) profile allow healthy honeybees to identify diseased nestmates, eliciting agonistic responses in the former. Here, we determined whether these 'immunologic cues' emitted by diseased nestmates were only detected by workers, who consequently took hygienic measures and excluded these individuals from the colony, or whether queens were also able to detect these cues and respond accordingly. Healthy honeybee queens were exposed to (i) healthy, (ii) Ringer-injected and (iii) lipopolysaccharide (LPS)-injected nestmates by allowing direct body contact. Quantitative differences in the CHC profiles of these three groups were measured using GC-MS. The transcript levels of the products of four genes that encode for antimicrobial peptides (AMPs), which are part of the queen's immune response, were measured in bees exposed to direct contact using qPCR. A significant increase in the transcript levels of these AMP genes over baseline levels in queens was observed when body contact was allowed between the queens and the Ringer-and LPS-injected nestmates. These results provide the first evidence that the detection of CHCs contributes to the initiation of an immune response in insects. In an additional experiment, CHCs were extracted from diseased workers and directly presented to queens, which also evoked a similar immune response. A potential mechanism that relied on volatile compounds could be ruled out by conducting a distance experiment. The study helps to expand our knowledge of chemical communication in insects and sheds light on a likely new mechanism of social immunity.

Behaviours indicating cannibalistic necrophagy in ants are modulated by the perception of pathogen infection level

“…These secretions can also be transmitted to other individuals by trophallaxis, improving their protection 69 . Such signals of an infection threat have already been described in other social insects, such as termites, that perform a vibrational display to increase their distance from the non-infected nestmates 70 , and honeybees, in which the cuticular chemical cues of the diseased nestmates can induce an immune response in queens 71 .…”

Destructive disinfection of infected brood prevents systemic disease spread in ant colonies

“…Upon detection, healthy animals usually respond by interacting with sick conspecifics less or avoiding them completely ( Poirotte et al, 2017 ; Kiesecker et al, 1999 ; Behringer et al, 2006 ; Anderson and Behringer, 2013 ). In addition, they may prophylactically increase the expression of their immune defences in preparation for a potential immune challenge ( Hernández López et al, 2017 ), and a similar phenomenon is observed in animals and plants in response to chemicals released by wounded conspecifics ( Heil and Silva Bueno, 2007 ; Peuß et al, 2015 ). Because there are downsides to being socially excluded, sick animals may, under some circumstances, attempt to hide their illness ( Lopes, 2014 ; Lopes et al, 2012 ).…”

The Mechanisms of Social Immunity Against Fungal Infections in Eusocial Insects

“…Chemoreception is able to facilitate social immunity by influencing not only the behavior defense, but also the physiological defense. In bees, societal members can immunize themselves by directly contacting with cuticular hydrocarbon (CHC) cues of immune-challenged workers [121,122,123], indicating a potential route to social immunization against bacterial pathogens in social insect societies. In addition, it has been reported that social transfer of low-dose fungal conidia promotes social immunization in social insects [14,62].…”