Density of Antennal Sensilla Influences Efficacy of Communication in a Social Insect

Abstract

Effective communication requires reliable signals and competent receptors. Theoretical and empirical accounts of animal signaling focus overwhelmingly on the capacity of the signaler to convey the message. Nevertheless, the intended receiver's ability to detect a signal depends on the condition of its receptor organs, as documented for humans. The impact of receptor organ condition on signal reception and its consequences for functional behavior are poorly understood. Social insects use antennae to detect chemical odors that distinguish between nestmates and enemies, reacting aggressively to the latter. We investigated the impact of antennal condition, determined by the density of sensilla, on the behavior of the weaver ant Oecophylla smaragdina. Worker aggression depended upon the condition of their antennae: workers with fewer sensilla on their antennae reacted less aggressively to nonnestmate enemies. These novel data highlight the largely unappreciated significance of receptor organ condition for animal communication and may have implications for coevolutionary processes in animal communication.

Solitary bees reduce investment in communication compared with their social relatives

“…The first is an increase in surface area, which could increase the speed of discrimination. Previous work with ants supports this prediction: Workers with a greater density of sensilla more accurately recognized nonnestmates and responded with greater levels of aggression than workers with fewer sensilla (37). The extra sensilla found in social species may also represent an increase in the variety of chemoreceptors present on the antennae without compromising sensitivity and could accommodate more precise or complex signals used in social interactions.…”

“…Importantly, the number and density of antennal sensilla influence the perception of social signals. For example, workers of Oecophylla ants with fewer sensilla are less aggressive to nonnestmates (37). Similarly, antennal sensilla density is positively correlated with increased sensitivity to chemical signals and with body size in some bee species (38,39).…”

Behavioral Performance and Neural Systems Are Robust to Sensory Injury in Workers of the Ant Pheidole dentata

“…In the few cases where it has been examined in ants, antennal condition has been shown to significantly impact worker task performance. Workers of the weaver ant Oecophylla smaragdina having fewer antennal sensilla, possibly due to antennal wear or damage, behave less aggressively toward nonnestmates, which presumably impairs their ability to defend territory [Gill et al, 2013]. Additionally, unilaterally antennectomized workers of the desert ant Cataglyphis fortis are unable to locate their nest entrance due to the lack of concurrent (stereo) olfactory information to both antennae [Steck et al, 2010].…”

“…First, synapsin upgregulation in AL projection neurons could follow any reduction in AL activity, including that caused by partial antennal nerve damage (or perhaps even after wear and degradation of individual antennal sensilla) [c.f., Gill et al, 2013]. In this case, synapsin upregulation would be a general homeostatic mechanism that increases the gain of remaining afferent olfactory information entering the ipsilateral MB calyces from a damaged antenna.…”

“…Given the great importance of chemosensation for navigation and task performance by ants, antennal damage could be particularly costly for Pheidole workers. For example, weaver ants with fewer antennal sensilla, likely reflective of antennal wear, are less aggressive nest defenders [Gill et al, 2013].…”