A context-dependent alarm signal in the antTemnothorax rugatulus

Abstract

Because collective cognition emerges from local signaling among group members, deciphering communication systems is crucial to understanding the underlying mechanisms. Alarm signals are widespread in the social insects and can elicit a variety of behavioral responses to danger, but the functional plasticity of these signals has not been well studied. Here we report an alarm pheromone in the ant Temnothorax rugatulus that elicits two different behaviors depending on context. When an ant was tethered inside an unfamiliar nest site and unable to move freely, she released a pheromone from her mandibular gland that signaled other ants to reject this nest as a potential new home, presumably to avoid potential danger. When the same pheromone was presented near the ants' home nest, they were instead attracted to it, presumably to respond to a threat to the colony. We used coupled gas chromatography/mass spectrometry to identify candidate compounds from the mandibular gland and tested each one in a nest choice bioassay. We found that 2,5-dimethylpyrazine was sufficient to induce rejection of a marked new nest and also to attract ants when released at the home nest. This is the first detailed investigation of chemical communication in the leptothoracine ants. We discuss the possibility that this pheromone's deterrent function can improve an emigrating colony's nest site selection performance. KEY WORDS: Alarm pheromone, Collective decision-making, Temnothorax INTRODUCTIONIn many taxa, from slime molds to humans, groups cooperatively process information to achieve collective cognition (Couzin, 2009;. By distributing the burden of cognition across many individuals, groups can assess their environment and make consensus decisions, oftentimes more rapidly and accurately than a solitary animal could do (Biro et al., 2006;Sasaki et al., 2013;Ward et al., 2011). Collective cognition emerges in non-obvious ways from a complex network of local interactions among group members. Understanding this process requires decoding the specialized signals that group members exchange in these interactions (Sumpter, 2010). Communication systems, and the group behavior they underlie, have reached especially great diversity and complexity in the eusocial insects (Hölldobler and Wilson, 2009;Seeley, 1989;Wheeler, 1912 bees has revealed much about the physical nature and information content of signals, and how they contribute to emergent colony properties (Franks, 1989;Hirsh and Gordon, 2001;Passino and Seeley, 2006;Pratt, 2005;Seeley and Buhrman, 2001;Seeley, 1997;Visscher, 2007).Most of this work has concerned recruitment signals used by successful foragers or nest site scouts, but another fundamental type of communication is alarm signaling. In social insects, defensive behavior is closely connected with alarm signals that either recruit nestmates to combat a potential danger or warn them to stay away (Blum, 1969;Crewe and Fletcher, 1974;Maschwitz, 1964). Besides an early report (Goetsch, 1953), the first thorough study of chemical alar...

Colony-level non-associative plasticity of alarm responses in the stingless honey bee, Tetragonisca angustula

“…Alarm pheromones are a common class of pheromones, which elicit defensive and escape behavior in social insects (Maschwitz 1964; Blum 1969). The nature of the response in any individual depends upon its caste and the context in which the alarm pheromone is presented (Maschwitz 1966; Shorey 1973; Sasaki et al 2014). At or near the colony, alarm pheromones elicit defensive behaviors, especially among specialized guard castes (Wilson 1965; Maschwitz 1966; Blum 1969; Sasaki et al 2014).…”

“…The nature of the response in any individual depends upon its caste and the context in which the alarm pheromone is presented (Maschwitz 1966; Shorey 1973; Sasaki et al 2014). At or near the colony, alarm pheromones elicit defensive behaviors, especially among specialized guard castes (Wilson 1965; Maschwitz 1966; Blum 1969; Sasaki et al 2014). Classically, honeybees sacrifice themselves in colony defense against mammals through stinging and subsequently eviscerating themselves to defend the colony (Hermann 1971).…”

Influence of colony associated factors on nest selection in an Indian queenless ant

“…In cases where she was tethered and the colony selected an alternate nest, tandem leaders continued to put their efforts in releasing her. In T. rugatulus alarm pheromone released by the tethered individual repels the selection of that site (Sasaki et al, 2014). We found that there was no significant difference between the number of times the site containing the tethered gamergate and free gamergate were chosen as the final nest.…”

“…In T. rugatulus alarm pheromone released by the tethered individual repels the selection of that site (Sasaki et al, 2014). In cases where she was tethered and the colony selected an alternate nest, tandem leaders continued to put their efforts in releasing her.…”

Task switching is associated with temporal delays inTemnothorax rugatulusants

“…Individuals may switch tasks because all of the work in the first task is now completed. Alternatively, signals or cues in other modalities could cause individuals to switch to a task that has higher demand (Sasaki et al 2014;Vander Meer et al 1998). Individuals may even interrupt a current task to assess the need of the colony, as seen in honeybees (Johnson 2008(Johnson , 2009); or they may be spontaneously ending tasks, as seen in T. albipennis individuals when building (Franks and Deneubourg 1997), to wander inside the nest to assess demand for other tasks.…”