Perception of cuticular hydrocarbons and their interpretation in an ant species

Animals collect environmental information for decision-making. The ability to perceive an environmental cue and distinguish it from the background does, however, not necessarily lead to the use of this cue for decision-making. We investigated the use of cuticular hydrocarbon cues for nestmate discrimination in ants. Like other insects, the cuticle of ants is covered by a complex mixture of hydrocarbons. These hydrocarbons are used by many ants to identify colony members and discriminate against foreign individuals. The question is whether all of these hydrocarbons are equally well perceived, distinguished from other hydrocarbons, and used for nestmate discrimination. We applied single-sensillum recording of the antenna, classical conditioning bioassays for compound discrimination abilities, and individual compound supplementation for a nestmate discrimination bioassay to investigate this question in workers of the ant Camponotus floridanus. We tested linear alkanes, methylbranched alkanes, and dimethylbranched alkanes. Single-sensillum recording revealed that the ant antennae were sensitive to all tested hydrocarbons without statistically significant differences. Classical conditioning bioassays demonstrated that all except one hydrocarbon could be distinguished from the alkane hentriacontane, which was used as a reference. When transferred on nestmate workers, hentriacontane elicited the lowest number of attacks, the lowest duration of attacks, and the highest latency of attacks. This demonstrates that hydrocarbons are not equally used for nestmate discrimination, despite similar sensillar sensitivities and well-developed abilities to distinguish hentriacontane from other compounds.